Method for the production of L-lysine employing thermophilic corynebacterium thermoaminogenes
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method for producing L-lysine by fermentation and to an L-lysine producing mutant. 
     2. Description of the Background 
     L-lysine, which is important as an additive for livestock feed, and the like has been mainly prepared by fermentation. 
     In the industrial preparation of L-lysine by fermentation, some technical factors must be considered in order to achieve economic improvement of the process. These factors include, for example, improvements in yield based on sugar, improvements in concentration of L-lysine which accumulates, shortening of culturing time, and the like. 
     In culturing, it is important to elevate the temperature for culturing. Culturing is generally carried out at an optimum temperature for L-lysine fermentation. Where conventional L-lysine-producing bacteria are used, the temperature is generally between 28° and 35° C. When culturing begins, the heat of fermentation is generated so that when the system is allowed to stand, the temperature of the culture medium increases with the result that the amount of L-lysine which forms seriously decreases. In order to maintain the temperature of the culture medium in the optimum range, it is necessary to mount a heat exchanger in the fermentation tank and cyclize cool water into the tank. In order to obtain cool water, a cooler must be used. However, since the heat of fermentation generated is very large, the amount of electric energy consumed by the cooler is very large. Accordingly, if the culture temperature for fermentation of L-lysine is increased, the cooling load decreases so that economy of L-lysine production in an industrial scale can be improved. 
     The method described in Korean Patent Publication No. 85-231 (published August 23, 1985) proposes to increase the culture temperature in the fermentation of L-lysine. That is, the method disclosed employs the L-lysine-producing variant TR-3579 (KFCC 10065) which belongs to the genus Corynebacterium, which has resistance to a lysine analogue and resistance to temperature and further requires homoserine, leucine and valine in combination. Culturing of the variant occurs in a medium at a high temperature (37° to 45° C), thereby producing and accumulating L-lysine in the culture medium. 
     Since the L-lysine-producing variant used in this method is obtained by improving conventional L-lysine-producing bacteria (grown at 30° to 35° C.) by a mutation which results in the production of L-lysine at a high temperature (37° to 45° C.). the variant has complex auxotrophy of homoserine, leucine and valine as described above, because of the several step mutation employed. Therefore, this method is not practical. 
     Japanese Patent Application Laid-Open No. 58-170487 discloses a method for producing L-lysine by fermentation which comprises culturing a mutant belonging to the genus Corynebacterium, having a reduced pyruvate kinase acivity, which is capable of producing L-lysine and also which has optional resistance to S-(2-aminoethyl)-L-cysteine in a medium thereby producing and accumulating L-lysine in the culture broth and then collecting L-lysine. 
     The temperature for fermentation in the method is set at 20° to 40° C., but as is assumed from the only working example (Example 1) in the reference where a temperature of 30° C. is adopted, the growth of the bacteria used is not significant at about 40° C. which is the upper limit of the temperature range for fermentation. Marked formation and accumulation of L-lysine are not observed either. This has been confirmed by experimentation. A need therefore continues to exist for an improved method of producing L-lysine by fermentation. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide bacteria which are capable of producing L-lysine by fermentation at a high temperature which can withstand practical use conditions. 
     Another object of the present invention is to provide a method for producing L-lysine by fermentation under practical conditions at a high temperature. 
     Briefly, these objects and other objects of the invention as hereinafter will become apparent can be attained in a method for producing L-lysine by fermentation which comprises culturing, in a medium, an L-lysine-producing mutant belonging to the genus Corynebacterium which is capable of growing even at 40° C. or higher and which has a resistance to S-(2-aminoethyl)-L-cysteine thereby producing and accumulating L-lysine in the culture medium and collecting L-lysine from the culture medium. 
     The invention also provides an L-lysine-producing mutant per se which can be advantageously utilized in the method described above for producing L-lysine by fermentation. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As a result of extensive investigations it has now been found that by using a mutant modified into L-lysine-producing bacteria by imparting AEC resistance to thermophilic bacteria belonging to the genus Corynebacterium which are capable of growing at 40° C. or higher, the objectives described above can be achieved. Based on this finding, the present invention has been accomplished. 
     The L-lysine-producing mutant of the invention which belongs to the genus Corynebacterium is capable of growing at 40° C. or higher and has AEC resistance. It is obtained by subjecting bacteria belonging to the genus Corynebacterium which are capable of growing at 40° C. or higher, such as for example, L-glutamic acid-producing bacteria, as the parent strain, to a mutation process. 
     Suitable parent strains include, for example, bacteria belonging to Corynebacterium thermoaminogenes which are described in Japanese Patent Applicant Laid-Open No. 63-240779 and which are isolated from nature. 
     There is no particular difficulty in collecting the L-lysine-producing mutant after subjecting the parent strain to a mutation process, but a conventionally known method for collecting a chemical-resistant mutant can be used. For example, the parent strain, which has been subjected to a mutation process with N-methyl N&#39;-nitro-N-nitrosoguanidine (250 ug/ml, 30° C., 30 minutes), or the like, is inoculated on an ordinary agar plate medium containing 1 to 2 g/dl of AEC in which the parent strain cannot be grown, and cultured at 40° C. or higher, e.g., 43° C. The resulting colony is collected and the desired mutant obtained. 
     Examples of the thus collected L-lysine-producing mutant include the following: Corynebacterium thermoaminogenes AJ 12521, Corynebacterium thermoaminogenes AJ 12522, Corynebacterium thermoaminogenes AJ 12523, and Corynebacterium thermoaminogenes AJ 12524. The bacteriological properties of these mutants are shown in Tables 1, 1 through 6. 
     Corynebacterium thermoaminogenes AJ 12308 and AJ 12309 which are parent strains, have been internationally deposited in the Fermentation Research Institute of the Agency of Industrial Science and Technology of Japan under Accession Nos. FERM BP-1540 and FERM BP-1541, respectively. Furthermore, the mutants Corynebacterium thermoaminogenes AJ 12521, AJ 12522, AJ 12523, and AJ 12524 have also been internationally deposited in the Fermentation Research Institute of the Agency of Industrial Science and Technology of Japan under Accession Nos.FERM BP-3304 , FERM BP-3305, FERM BP-3306 and FERM BP-3307, respectively. 
     
                                           TABLE 1-1                               
__________________________________________________________________________
                  Mutant          Parent Strain                           
                                          Mutant                          
          Parent Strain                                                   
                  AJ 12521                                                
                          AJ 12522                                        
                                  AJ 12309                                
                                          AJ 12523                        
                                                  AJ 12524                
          AJ 12308                                                        
                  FERM    FERM    FERM    FERM    FERM                    
          FERM BP-1540                                                    
                  BP-3304 BP-3305 BP-1541 BP-3306 BP-3307                 
__________________________________________________________________________
Shape:                                                                    
(1)                                                                       
  Shape and                                                               
          Rod of 0.7-                                                     
                  Rod of 0.7-                                             
                          Rod of 0.7-                                     
                                  Rod of 0.7-                             
                                          Rod of 0.7-                     
                                                  Rod of 0.7-             
  size of cell                                                            
          1.0 × 1.0-4.0                                             
                  1.0 × 1.0-4.0                                     
                          1.0 × 1.0-4.0                             
                                  1.0 × 1.0-4.0                     
                                          1.0 × 1.0-4.0             
                                                  1.0 × 1.0-4.0     
          μm; Cell edges                                               
                  μm; Cell edges                                       
                          μm; Cell edges                               
                                  μm; Cell edges                       
                                          μm; Cell edges               
                                                  μm; Cell edges       
          are rounded.                                                    
                  are rounded.                                            
                          are rounded.                                    
                                  are rounded.                            
                                          are rounded.                    
                                                  are rounded.            
          V-shaped con-                                                   
                  V-shaped con-                                           
                          V-shaped con-                                   
                                  V-shaped con-                           
                                          V-shaped con-                   
                                                  V-shaped con-           
          figuration based                                                
                  figuration based                                        
                          figuration based                                
                                  figuration based                        
                                          figuration based                
                                                  figuration based        
          on snapping                                                     
                  on snapping                                             
                          on snapping                                     
                                  on snapping                             
                                          on snapping                     
                                                  on snapping             
          division is                                                     
                  division is                                             
                          division is                                     
                                  division is                             
                                          division is                     
                                                  division is             
          noted.  noted.  noted.  noted.  noted.  noted.                  
(2)                                                                       
  Polymorphism                                                            
          No poly-                                                        
                  No poly-                                                
                          No poly-                                        
                                  No poly-                                
                                          No poly-                        
                                                  No poly-                
          morphism is                                                     
                  morphism is                                             
                          morphism is                                     
                                  morphism is                             
                                          morphism is                     
                                                  morphism is             
          noted but de-                                                   
                  noted but de-                                           
                          noted but de-                                   
                                  noted but de-                           
                                          noted but de-                   
                                                  noted but de-           
          pending on the                                                  
                  pending on the                                          
                          pending on the                                  
                                  pending on the                          
                                          pending on the                  
                                                  pending on the          
          phase of incu-                                                  
                  phase of incu-                                          
                          phase of incu-                                  
                                  phase of incu-                          
                                          phase of incu-                  
                                                  phase of incu-          
          bation, long rod                                                
                  bation, long rod                                        
                          bation, long rod                                
                                  bation, long rod                        
                                          bation, long rod                
                                                  bation, long rod        
          cells, mast cells                                               
                  cells, mast cells                                       
                          cells, mast cells                               
                                  cells, mast cells                       
                                          cells, mast cells               
                                                  cells, mast cells       
          and premature                                                   
                  and premature                                           
                          and premature                                   
                                  and premature                           
                                          and premature                   
                                                  and premature           
          cells are rarely                                                
                  cells are rarely                                        
                          cells are rarely                                
                                  cells are rarely                        
                                          cells are rarely                
                                                  cells are rarely        
          noted.  noted.  noted.  noted.  noted.  noted.                  
(3)                                                                       
  Motility                                                                
          None    None    None    None    None    None                    
(4)                                                                       
  Spore   None    None    None    None    None    None                    
(5)                                                                       
  Gram Staining                                                           
          Positive                                                        
                  Positive                                                
                          Positive                                        
                                  Positive                                
                                          Positive                        
                                                  Positive                
(6)                                                                       
  Antacid Negative                                                        
                  Negative                                                
                          Negative                                        
                                  Negative                                
                                          Negative                        
                                                  Negative                
__________________________________________________________________________
 
    
     
                                           TABLE 1-2                               
__________________________________________________________________________
         Parent Strain                                                    
                  Mutant            Parent Strain                         
                                             Mutant                       
         AJ 12308 AJ 12521 AJ 12522 AJ 12309 AJ 12523 AJ                  
__________________________________________________________________________
                                                      12524               
Physiological                                                             
properties:                                                               
(1)                                                                       
  Bouillon agar                                                           
         Abundant or mod-                                                 
                  Abundant or mod-                                        
                           Abundant or mod-                               
                                    Abundant or mod-                      
                                             Abundant or                  
                                                      Abundant or mod-    
  plate culture                                                           
         erate growth;                                                    
                  erate growth;                                           
                           erate growth;                                  
                                    erate growth;                         
                                             erate growth;                
                                                      erate growth;       
         Colonies are cir-                                                
                  Colonies are cir-                                       
                           Colonies are cir-                              
                                    Colonies are cir-                     
                                             Colonies are                 
                                                      Colonies are cir-   
         cular, smooth, en-                                               
                  cular, smooth, en-                                      
                           cular, smooth, en-                             
                                    cular, smooth, en-                    
                                             cular, smooth,               
                                                      cular, smooth, en-  
         tire convex,                                                     
                  tire convex,                                            
                           tire convex,                                   
                                    tire convex,                          
                                             tire convex,                 
                                                      tire convex,        
         glossy,  glossy,  glossy,  glossy,  glossy,  glossy,             
         opaque or trans-                                                 
                  opaque or trans-                                        
                           opaque or trans-                               
                                    opaque or trans-                      
                                             opaque or trans-             
                                                      opaque or trans-    
         lucent, dull                                                     
                  lucent, dull                                            
                           lucent, dull                                   
                                    lucent, dull                          
                                             lucent, dull                 
                                                      lucent, dull        
         yellow butyrous.                                                 
                  yellow butyrous.                                        
                           yellow butyrous.                               
                                    yellow butyrous.                      
                                             yellow butyrous.             
                                                      yellow butyrous.    
(2)                                                                       
  Bouillon agar                                                           
         Abundant or mod-                                                 
                  Abundant or mod-                                        
                           Abundant or mod-                               
                                    Abundant or mod-                      
                                             Abundant or                  
                                                      Abundant or mod-    
  slant culture                                                           
         erate growth;                                                    
                  erate growth;                                           
                           erate growth;                                  
                                    erate growth;                         
                                             erate growth;                
                                                      erate growth;       
         filiform, glossy,                                                
                  filiform, glossy,                                       
                           filiform, glossy,                              
                                    filiform, glossy,                     
                                             filiform, glossy,            
                                                      filiform, glossy,   
         dull yellow                                                      
                  dull yellow                                             
                           dull yellow                                    
                                    dull yellow                           
                                             dull yellow                  
                                                      dull yellow         
(3)                                                                       
  Bouillon                                                                
         Moderate growth;                                                 
                  Moderate growth;                                        
                           Moderate growth;                               
                                    Moderate growth;                      
                                             Moderate growth;             
                                                      Moderate growth;    
  liquid colony becomes                                                   
                  colony becomes                                          
                           colony becomes                                 
                                    colony becomes                        
                                             colony becomes               
                                                      colony becomes      
  culture                                                                 
         turbid almost                                                    
                  turbid almost                                           
                           turbid almost                                  
                                    turbid almost                         
                                             turbid almost                
                                                      turbid almost       
         uniformly but                                                    
                  uniformly but                                           
                           uniformly but                                  
                                    uniformly but                         
                                             uniformly but                
                                                      uniformly but       
         some cells                                                       
                  some cells                                              
                           some cells                                     
                                    some cells                            
                                             some cells                   
                                                      some cells          
         precipitate.                                                     
                  precipitate.                                            
                           precipitate.                                   
                                    precipitate.                          
                                             precipitate.                 
                                                      precipitate.        
(4)                                                                       
  Bouillon                                                                
         Moderate growth;                                                 
                  Moderate growth;                                        
                           Moderate growth;                               
                                    Moderate growth;                      
                                             Moderate growth;             
                                                      Moderate growth;    
  gelatin stab                                                            
         no gelatin is                                                    
                  no gelatin is                                           
                           no gelatin is                                  
                                    no gelatin is                         
                                             no gelatin                   
                                                      no gelatin is       
  culture                                                                 
         liquefied.                                                       
                  liquefied.                                              
                           liquefied.                                     
                                    liquefied.                            
                                             liquefied.                   
                                                      liquefied.          
(5)                                                                       
  Litmus milk                                                             
         Slightly weakly                                                  
                  Slightly weakly                                         
                           Slightly weakly                                
                                    Slightly weakly                       
                                             Slightly weakly              
                                                      Slightly weakly     
         alkaline; Neither                                                
                  alkaline; Neither                                       
                           alkaline; Neither                              
                                    alkaline; Neither                     
                                             alkaline; Neither            
                                                      alkaline; Neither   
         liquefaction nor                                                 
                  liquefaction nor                                        
                           liquefaction nor                               
                                    liquefaction nor                      
                                             liquefaction                 
                                                      liquefaction nor    
         solidification is                                                
                  solidification is                                       
                           solidification is                              
                                    solidification is                     
                                             solidification               
                                                      solidification is   
         noted.   noted.   noted.   noted.   noted.   noted.              
__________________________________________________________________________
 
    
     
                                           TABLE 1-3                               
__________________________________________________________________________
            Parent Strain                                                 
                    Mutant           Parent Strain                        
                                              Mutant                      
            AJ 12308                                                      
                    AJ 12521 AJ 12522                                     
                                     AJ 12309 AJ 12523                    
                                                      AJ                  
__________________________________________________________________________
                                                      12524               
Physiological                                                             
properties:                                                               
(1)                                                                       
  Reduction of                                                            
            Positive                                                      
                    Positive Positive                                     
                                     Positive Positive                    
                                                      Positive            
  nitrate                                                                 
(2)                                                                       
  Denitration                                                             
            Negative                                                      
                    Negative Negative                                     
                                     Negative Negative                    
                                                      Negative            
(3)                                                                       
  MR test   Negative or                                                   
                    Negative or                                           
                             Negative or                                  
                                     Negative or                          
                                              Negative or                 
                                                      Negative or         
            slight positive                                               
                    slight positive                                       
                             slight positive                              
                                     slight positive                      
                                              slight positive             
                                                      slight positive     
(4)                                                                       
  VP test   Positive                                                      
                    Positive Positive                                     
                                     Positive Positive                    
                                                      Positive            
(5)                                                                       
  Indole formation                                                        
            Negative                                                      
                    Negative Negative                                     
                                     Negative Negative                    
                                                      Negative            
(6)                                                                       
  Formation of                                                            
            Positive                                                      
                    Positive Positive                                     
                                     Positive Positive                    
                                                      Positive            
  hydrogen sulfide                                                        
(7)                                                                       
  Starch hydrolysis                                                       
            Negative                                                      
                    Negative Negative                                     
                                     Negative Negative                    
                                                      Negative            
(8)                                                                       
  Utilization of                                                          
            Does not grow                                                 
                    Does not grow                                         
                             Does not grow                                
                                     Does not grow                        
                                              Does not grow               
                                                      Does not grow       
  citrate   in Koser me-                                                  
                    in Koser me-                                          
                             in Koser me-                                 
                                     in Koser me-                         
                                              in Koser me-                
                                                      in Koser me-        
            dium but grows                                                
                    dium but grows                                        
                             dium but grows                               
                                     dium but grows                       
                                              dium but grows              
                                                      dium but grows      
            in Christensen                                                
                    in Christensen                                        
                             in Christensen                               
                                     in Christensen                       
                                              in Christensen              
                                                      in Christensen      
            medium; ren-                                                  
                    medium; ren-                                          
                             medium; ren-                                 
                                     medium; ren-                         
                                              medium; ren-                
                                                      medium; ren-        
            ders medium                                                   
                    ders medium                                           
                             ders medium                                  
                                     ders medium                          
                                              ders medium                 
                                                      ders medium         
            alkaline.                                                     
                    alkaline.                                             
                             alkaline.                                    
                                     alkaline.                            
                                              alkaline.                   
                                                      alkaline.           
(9)                                                                       
  Utilization of                                                          
            Does not utilize                                              
                    Does not utilize                                      
                             Does not utilize                             
                                     Does not utilize                     
                                              Does not utilize            
                                                      Does not utilize    
  inorganic nitrates but util-                                            
                    nitrates but util-                                    
                             nitrates but util-                           
                                     nitrates but util-                   
                                              nitrates but                
                                                      nitrates but util-  
  nitrogen  izes ammonium                                                 
                    izes ammonium                                         
                             izes ammonium                                
                                     izes ammonium                        
                                              izes ammonium               
                                                      izes ammonium       
            salts.  salts.   salts.  salts.   salts.  salts.              
__________________________________________________________________________
 
    
     
                                           TABLE 1-5                               
__________________________________________________________________________
        Parent Strain                                                     
               Mutant    Parent Strain                                    
                                Mutant                                    
        AJ 12308                                                          
               AJ 12521                                                   
                    AJ 12522                                              
                         AJ 12309                                         
                                AJ 12523                                  
                                     AJ 12524                             
__________________________________________________________________________
(17) Acid formation                                                       
from sugar:                                                               
 1 L-Arabinose                                                            
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
 2 D-Xylose                                                               
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
 3 D-Glucose                                                              
        Positive                                                          
               Positive                                                   
                    Positive                                              
                         Positive                                         
                                Positive                                  
                                     Positive                             
 4 D-Mannose                                                              
        Positive                                                          
               Positive                                                   
                    Positive                                              
                         Positive                                         
                                Positive                                  
                                     Positive                             
 5 D-Fructose                                                             
        Positive                                                          
               Positive                                                   
                    Positive                                              
                         Positive                                         
                                Positive                                  
                                     Positive                             
 6 D-Galactose                                                            
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
 7 Maltose                                                                
        Positive                                                          
               Positive                                                   
                    Positive                                              
                         Positive                                         
                                Positive                                  
                                     Positive                             
 8 Sucrose                                                                
        Positive                                                          
               Positive                                                   
                    Positive                                              
                         Positive                                         
                                Positive                                  
                                     Positive                             
 9 Lactose                                                                
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
10 Trehalose                                                              
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
11 D-Sorbitol                                                             
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
12 D-Mannitol                                                             
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
13 Inositol                                                               
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
14 Glycerine                                                              
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
15 Starch                                                                 
        Negative                                                          
               Negative                                                   
                    Negative                                              
                         Negative                                         
                                Negative                                  
                                     Negative                             
__________________________________________________________________________
 
    
     
                                           TABLE 1-6                               
__________________________________________________________________________
             Parent Strain                                                
                     Mutant          Parent Strain                        
                                              Mutant                      
             AJ 12308                                                     
                     AJ 12521                                             
                             AJ 12522                                     
                                     AJ 12309 AJ 12523                    
                                                      AJ                  
__________________________________________________________________________
                                                      12524               
Other                                                                     
characterisitcs:                                                          
(1)                                                                       
  Temperature                                                             
             By capillary                                                 
                     By capillary                                         
                             By capillary                                 
                                     By capillary                         
                                              By capillary                
                                                      By capillary        
  resistance method in                                                    
                     method in                                            
                             method in                                    
                                     method in                            
                                              method in                   
                                                      method in           
             skimmed milk:                                                
                     skimmed milk:                                        
                             skimmed milk:                                
                                     skimmed milk:                        
                                              skimmed milk:               
                                                      skimmed milk:       
             Alive ab 60° C.,                                      
                     Alive ab 60° C.,                              
                             Alive ab 60° C.,                      
                                     Alive ab 60° C.,              
                                              Alive ab 60°         
                                                      Alive ab 60° 
                                                      C.,                 
             10 mins.                                                     
                     10 mins.                                             
                             10 mins.                                     
                                     10 mins. 10 mins.                    
                                                      10 mins.            
             Dead ab 65° C.,                                       
                     Dead ab 65° C.,                               
                             Dead ab 65° C.,                       
                                     Dead ab 65° C.,               
                                              Dead ab 65° C.,      
                                                      Dead ab 65°  
                                                      C.,                 
             10 mins.                                                     
                     10 mins.                                             
                             10 mins.                                     
                                     10 mins. 10 mins.                    
                                                      10 mins.            
(2)                                                                       
  Sodium chloride                                                         
             Grows in                                                     
                     Grows in                                             
                             Grows in                                     
                                     Grows in Grows in                    
                                                      Grows in            
  resistance medium con-                                                  
                     medium con-                                          
                             medium con-                                  
                                     medium con-                          
                                              medium con-                 
                                                      medium con-         
             taining 5%                                                   
                     taining 5%                                           
                             taining 5%                                   
                                     taining 5%                           
                                              taining 5%                  
                                                      taining 5%          
             saline. saline. saline. saline.  saline. saline.             
(3)                                                                       
  Nutrient   Requires biotin                                              
                     Requires biotin                                      
                             Requires biotin                              
                                     Requires biotin                      
                                              Requires biotin             
                                                      Requires biotin     
  auxotrophy for growth.                                                  
                     for growth.                                          
                             for growth.                                  
                                     for growth.                          
                                              for growth.                 
                                                      for growth.         
(4)                                                                       
  Nucleotide 60.2% GC                                                     
                     60.2% GC                                             
                             60.2% GC                                     
                                     59.5% GC 59.5% GC                    
                                                      59.5% GC            
  composition of                                                          
  DNA (Tm method)                                                         
(5)                                                                       
  Dibasic amino                                                           
             Meso-   Meso-   Meso-   Meso-    Meso-   Meso-               
  acid contained                                                          
             diaminopimelic                                               
                     diaminopimelic                                       
                             diaminopimelic                               
                                     diaminopimelic                       
                                              diaminopimelic              
                                                      diaminopimelic      
  in cell wall                                                            
             acid    acid    acid    acid     acid    acid                
(6)                                                                       
  Source     Fruit   --      --      Vegetable                            
                                              --      --                  
__________________________________________________________________________
 
    
     
                                           TABLE 1-4                               
__________________________________________________________________________
            Parent Strain                                                 
                    Mutant           Parent Strain                        
                                              Mutant                      
            AJ 12308                                                      
                    AJ 12521 AJ 12522                                     
                                     AJ 12309 AJ 12523                    
                                                      AJ                  
__________________________________________________________________________
                                                      12524               
(10)                                                                      
   Pigment  No pigment is                                                 
                    No pigment is                                         
                             No pigment is                                
                                     No pigment is                        
                                              No pigment                  
                                                      No pigment is       
   formation                                                              
            formed extra-                                                 
                    formed extra-                                         
                             formed extra-                                
                                     formed extra-                        
                                              formed extra-               
                                                      formed extra-       
            cellularly.                                                   
                    cellularly.                                           
                             cellularly.                                  
                                     cellularly.                          
                                              cellularly.                 
                                                      cellularly.         
(11)                                                                      
   Urease test                                                            
            Negative or                                                   
                    Negative or                                           
                             Negative or                                  
                                     Negative or                          
                                              Negative or                 
                                                      Negative or         
            slightly positive                                             
                    slightly positive                                     
                             slightly positive                            
                                     slightly positive                    
                                              slightly positive           
                                                      slightly positive   
(12)                                                                      
   Oxidase  Negative                                                      
                    Negative Negative                                     
                                     Negative Negative                    
                                                      Negative            
(13)                                                                      
   Catalase Positive                                                      
                    Positive Positive                                     
                                     Positive Positive                    
                                                      Positive            
(14)                                                                      
   Growth range                                                           
            Grows well at                                                 
                    Grows well at                                         
                             Grows well at                                
                                     Grows well at                        
                                              Grows well                  
                                                      Grows well at       
            Ph 7-8.5;                                                     
                    Ph 7-8.5;                                             
                             Ph 7-8.5;                                    
                                     Ph 7-8.5;                            
                                              Ph 7-8.5;                   
                                                      Ph 7-8.5;           
            grows well at                                                 
                    grows well at                                         
                             grows well at                                
                                     grows well at                        
                                              grows well                  
                                                      grows well at       
            35-45° C.;                                             
                    35-45° C.;                                     
                             35-45° C.;                            
                                     35-45° C.;                    
                                              35-45° C.;           
                                                      35-45° C.;   
            grows slightly                                                
                    grows slightly                                        
                             grows slightly                               
                                     grows slightly                       
                                              grows slightly              
                                                      grows slightly      
            at 46-50° C.                                           
                    at 46-50° C.                                   
                             at 46-50° C.                          
                                     at 46-50° C.                  
                                              at 46-50° C.         
                                                      at 46-50°    
                                                      C.                  
(15)                                                                      
   Behavior to                                                            
            Aerobic or                                                    
                    Aerobic or                                            
                             Aerobic or                                   
                                     Aerobic or                           
                                              Aerobic or                  
                                                      Aerobic or          
   oxygen   facultative                                                   
                    facultative                                           
                             facultative                                  
                                     facultative                          
                                              facultative                 
                                                      facultative         
            anerobic                                                      
                    anerobic anerobic                                     
                                     anerobic anerobic                    
                                                      anerobic            
(16)                                                                      
   O-F test Grows fer-                                                    
                    Grows fer-                                            
                             Grows fer-                                   
                                     Grows fer-                           
                                              Grows fer-                  
                                                      Grows fer-          
   (glucose)                                                              
            mentatively to                                                
                    mentatively to                                        
                             mentatively to                               
                                     mentatively to                       
                                              mentatively                 
                                                      mentatively to      
            form acid.                                                    
                    form acid.                                            
                             form acid.                                   
                                     form acid.                           
                                              form acid.                  
                                                      form                
__________________________________________________________________________
                                                      acid.               
 
    
     The medium used for producing and accumulating L-lysine using the present L-lysine-producing mutant, may be any conventional known medium for producing L-lysine. Conventional media containing carbon sources, nitrogen sources, inorganic salts, and, if necessary, other organic trace nutrients which the microorganism uses, can be used. Any carbon source may be used so long as the mutant used can use the same. Examples of the carbon sources include glucose, sucrose, maltose, starch hydrolysates containing them, sugars such as molasses, and the like; alcohols such as ethanol, propanol and the like; organic acids such as acetic acid, propionic acid, and the like. In addition, normal paraffin, and the like may also be used singly or in combination with other carbon sources, depending on the strain. As nitrogen sources, inorganic and organic nitrogen sources may be used including ammonium salts such as ammonium acetate, ammonium chloride, ammonium phosphate, and the like., nitrates, urea, ammonia, and furthermore, meat extract, and the like. Suitable inorganic salts include KH 2  PO 4 , MgSO 4 , FeSO 4 , MnSO 4  and the like which are ordinarily used. Suitable organic trace nutrients include vitamins, fatty acids and nucleic acids, and peptone, casamino acid, yeast extract or protein hydrolysate containing them. 
     Incubation is preferably carried out under aerobic conditions. By carrying out shake culture or aerial spinner culture for 2 to 4 days, and adjusting the pH of the medium to a range from 5 to 9, preferably 7 to 8.5 at the growth temperature of the bacteria used, i.e., about 25° to about 50° C., preferably about 35° to about 45° C. in order to achieve high L-lysine productivity, L-lysine can be produced and accumulated in the culture medium in a marked quantity. 
     Conventional methods for collecting L-lysine from the culture medium can be used. For example, L-lysine may be recovered by the conventional ion exchange resin method, crystallization, or the like in an appropriate combination. 
     As described above, the temperature for fermentation of L-lysine in accordance with the present invention is at the growth temperature of bacteria used, namely about 25° to about 50° C., preferably 35° to 45° C. at which L-lysine productivity increases. Examples 2 and 3 actually demonstrate that L-lysine was formed and accumulated in a remarkable quantity, by regulating the fermentation temperature at 43° C. on a laboratory scale. 
     Based on the experimental results, the cooling load for removing heat generated by fermentation on a commercial scale was calculated by trial. In the event that fermentation of L-lysine was performed using a fermentation tank having a volume of, e.g., 200 kiloliters, the cooling load for maintaining the optimum fermentation temperature, e.g., 30° C., for L-lysine-producing bacteria was 30 millionkilocalories per batch, whereas in the present invention the cooling load for maintaining the fermentation temperature not exceeding 43° C. was 3 million kilocalories per batch, when the L-lysine-producing mutant of the present invention was used. As is clear from the above data, the cooling load can be reduced by 90% by the method of the present invention. 
    
    
     Having now generally described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein. 
     EXAMPLE 1 
     (harvest of mutant) 
     After Corynebacterium thermoaminogenes AJ 12308 was treated with N-methyl-N-nitro-N-nitrosoguanidine (250 μg/ml, 30° C., 30 minutes) in a conventional manner, incubation was conducted at 43° C. in a medium obtained by supplementing the minimum medium below with 1.5 g/dl of AEC. Colonies grown at 43° C. in the medium were harvested. 
     
         ______________________________________                                    
Composition of minimum medium:                                            
______________________________________                                    
Glucose          2.0          g/dl                                        
Urea             0.25         g/dl                                        
Ammonium sulfate 1.0          g/dl                                        
KH.sub.2 PO.sub.4                                                         
                 0.1          g/dl                                        
MgSO.sub.4.7H.sub.2 O                                                     
                 0.04         g/dl                                        
FeSO.sub.4.7H.sub.2 O                                                     
                 1.0          mg/dl                                       
L-Alanine        50           mg/dl                                       
Nicotinamide     0.5          mg/dl                                       
MnSO.sub.4.4H.sub.2 O                                                     
                 1.0          mg/dl                                       
Biotin           5.0          μg/dl                                    
Thiamine hydrochloride                                                    
                 10           μg/dl                                    
NaCl             5            mg/dl                                       
pH 7.2                                                                    
______________________________________                                    
 
    
     Among the mutants thus obtained, AJ 12521 and AJ 12522 were harvested as mutants having excellent L-lysine productivity. 
     In a similar manner, AJ 12523 and AJ 12524 were harvested using Corynebacterium thermoaminogenes AJ 12309 as the parent strain. 
     The four mutants thus obtained were previously grown on glucose-bouillon agar medium at 43° C. One platinum loop aliquotos were inoculated respectively on 20 ml of sterile medium charged into a shaking flask of 500 ml volume and having the following composition. 
     
         ______________________________________                                    
Composition of medium:                                                    
______________________________________                                    
Beat molasses       10         g/dl                                       
Ammonium sulfate    5          g/dl                                       
KH.sub.2 PO.sub.4   0.1        g/dl                                       
MgSO.sub.4.7H.sub.2 O                                                     
                    40         mg/dl                                      
Biotin              50         μg/dl                                   
Calcium carbonate (separately                                             
                    5          g/dl                                       
sterilized and added)                                                     
pH 7.0                                                                    
______________________________________                                    
 
    
     These mutants were cultured at 43° C. for 72 hours. Lysine was accumulated as shown in Table 2. 
     
                       TABLE 2                                                     
______________________________________                                    
Strain   Concentration of L-lysine accumulated (g/dl)                     
______________________________________                                    
AJ 12521 3.2                                                              
AJ 12522 2.9                                                              
AJ 12523 2.8                                                              
AJ 12524 3.0                                                              
______________________________________                                    
 
    
     EXAMPLE 2 
     In a shaking 500 ml volume flask, 20 ml of aqueous medium having the following composition was separately charged followed by sterilization at 110° C. for 10 minutes with steam. 
     
         ______________________________________                                    
Composition of medium:                                                    
______________________________________                                    
Glucose          10           g/dl                                        
Ammonium sulfate 4.5          g/dl                                        
KH.sub.2 PO.sub.4                                                         
                 0.1          g/dl                                        
MgSO.sub.4.7H.sub.2 O                                                     
                 0.04         g/dl                                        
FeSO.sub.4.7H.sub.2 O                                                     
                 1.0          mg/dl                                       
MnSO.sub.4.4H.sub.2 O                                                     
                 1.0          mg/dl                                       
Biotin           5.0          μg/dl                                    
Thiamine hydrochloride                                                    
                 20           μg/dl                                    
Concentrate of soybean                                                    
                 1.5          ml/dl                                       
protein hydrolysate                                                       
with hydrochloric acid                                                    
(total nitrogen, 7%)                                                      
Calcium carbonate                                                         
                 5            g/ml                                        
(separately sterilized                                                    
and added)                                                                
pH 7.0                                                                    
______________________________________                                    
 
    
     One platinum loop of Corynebacterium thermoaminogenes AJ 12521 which had been previously grown on a glucose bouillon slant was inoculated on the thus prepared medium charged in a flask. Shaking culture was conducted at 43° C. for 72 hours. 
     The amount of L-lysine produced in the medium after culturing for 72 hours was colorimetrically determined using the ninhydrin reaction. The results indicate that L-lysine was produced in an amount of 3.0 g/dl. 
     Furthermore, solutions corresponding to 50 flasks cultured in a similar manner which completed incubation were collected and the cells and calcium salt were removed by centrifugation. About 1 liter of the thus obtained supernatant was passed through a strongly acidic ion exchange resin (AMBERLITE&#34; IR-120 (OH type)) to adsorb L-lysine thereonto. The adsorbed L-lysine was eluted with 3% ammonia water and the eluate was concentrated under reduced pressure. After hydrochloric acid was added to the concentrate, the mixture was cooled and L-lysine was precipitated as L-lysine hydrochloride dihydrate to give 26.5 g of crystals. 
     EXAMPLE 3 
     One platinum loop each of Corynebacterium thermoaminogenes AJ 12523 and the parent strain AJ 12309 Was taken from the slant and inoculated on 50 ml of the aqueous seed culture medium described below. Aerial spinner culturing was performed at 43° C. for 18 hours to prepare a seed culture medium. 
     
         ______________________________________                                    
Composition of seed culture medium:                                       
______________________________________                                    
Glucose          1.5          g/dl                                        
Ammonium sulfate 0.3          g/dl                                        
Urea             0.1          g/dl                                        
KH.sub.2 PO.sub.4                                                         
                 0.1          g/dl                                        
MgSO.sub.4.7H.sub.2 O                                                     
                 0.04         g/dl                                        
FeSO.sub.4.7H.sub.2 O                                                     
                 1.0          mg/dl                                       
MnSO.sub.4.4H.sub.2 O                                                     
                 1.0          mg/dl                                       
Biotin           5.0          μg/dl                                    
Thiamine hydrochloride                                                    
                 20           μg/dl                                    
Concentrate of soybean                                                    
                 2.0          ml/dl                                       
protein hydrolysate                                                       
with hydrochloric acid                                                    
(total nitrogen, 7%)                                                      
pH 7.5                                                                    
______________________________________                                    
 
    
     On the other hand, 300 ml aliquots of aqueous medium for main fermentation having the composition described below were each charged into a glass-made jar fermenter of 1 liter volume and sterilized in a conventional manner. 
     Each medium was inoculated with 15 ml of the seed culture medium and aerial spinner culturing was initiated at 43° C. 
     
         ______________________________________                                    
Composition of medium for main fermentation:                              
______________________________________                                    
Glucose          2.0          g/dl                                        
Ammonium sulfate 0.5          g/dl                                        
Urea             0.2          g/dl                                        
KH.sub.2 PO.sub.4                                                         
                 0.1          g/dl                                        
MgSO.sub.4.7H.sub.2 O                                                     
                 0.04         g/dl                                        
FeSO.sub.4.7H.sub.2 O                                                     
                 1.0          mg/dl                                       
MnSO.sub.4.4H.sub.2 O                                                     
                 1.0          mg/dl                                       
Biotin           5.0          μg/dl                                    
Thiamine hydrochloride                                                    
                 50           μg/dl                                    
Nicotinamide     1.0          mg/dl                                       
Concentrate of soybean                                                    
                 3.0          ml/dl                                       
protein hydrolysate                                                       
with hydrochloric acid                                                    
(total nitrogen, 7%)                                                      
pH 7.2                                                                    
______________________________________                                    
 
    
     A mixture of acetic acid and ammonium acetate (molar ratio of acetic acid:ammonium acetate in the mixture was 1:0.25; concentration of acetic acid in the mixture was 60%) was added to the culture medium to maintain the pH of the medium between 7.2 and 8.0. Incubation was performed at 43° C. for 55 hours. 
     The results are shown in Table 3. 
     
                       TABLE 3                                                     
______________________________________                                    
             Amount of L-Lysine                                           
Strain Used  Accumulated (g/dl)                                           
______________________________________                                    
AJ 12523     3.2                                                          
AJ 12309     0.03                                                         
(parent)                                                                  
______________________________________                                    
 
    
     From 300 ml of the solution obtained after completion of fermentation of AJ 12323, 1.0 g of L-lysine hydrochloride dihydrate was obtained as crystals in a manner similar to Example 2. 
     EXAMPLE 4 
     In a shaking flask of 500 ml volume, 20 ml of the same medium as used in Example 2 was charged followed by sterilization at 110° C. for 10 minutes with steam. One platinum loop of Corynebacterium thermoaminogenes AJ 12524, which had been previously grown on glucose-bouillon slant, was inoculated on the medium followed by shaking culturing at 43° C. for 50 hours. 
     After 0.2 ml of the culture medium was charged into a glass-made jar fermenter, 5 ml of cooled physiological saline was added thereto. After stirring, the mixture was centrifuged at 4500 rpm for 10 minutes and the supernatant was discharged. 
     A mixture of 1.5 ml of 0.2 M phosphate buffer (pH 7.5) and 1.5 ml of the reaction solution described below was added and the mixture was stirred. The cells were suspended followed by a shaking reaction (120 rpm) at 43° C. for 2 hours. 
     
         ______________________________________                                    
Reaction solution:                                                        
______________________________________                                    
Glucose        1             g/dl                                         
(NH.sub.4).sub.2 SO.sub.4                                                 
               0.4           g/dl                                         
MgSO.sub.4.7H.sub.2 O                                                     
               0.04          g/dl                                         
Biotin         500           μg/dl                                     
pH 7.5                                                                    
______________________________________                                    
 
    
     Thereafter, centrifugation (4500 rpm, 10 minutes) was carried out and the concentration of L-lysine in the supernatant was analyzed by liquid chromatography. The results showed that 0.2 g/dl of L-lysine had accumulated. 
     The present invention provides a method for producing L-lysine on a industrial scale in which the cooling load for eliminating heat generated upon fermentation is reduced. Further, the method requires no amino acid nutrients and can be practically used. 
     Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.