the organism was isolated from a soil sample collected from rajshahi , bangladesh at the depth of 0.75 m using crowded plate technique ( hammond and lambert , 1978 ) .
the organism was identified as a novel , streptomyces species on the basis of morphological , physiological , biochemical ( shirling and gottlieb , 1969 ) and 16s rdna studies ( genbank accession number bankit1256035 gq500975 ) and designated as streptomyces sp .
pure culture of the strain was maintained on czapek dox ( alkaline ) agar slant .
shake flask fermentations were run in 500 ml flasks containing 100 ml czapek - dox ( alkaline ) broth .
the flasks were allowed to cool and the liquid media inoculated with spores of the organisms from previously prepared agar slant were poured into it
. then they were incubated at 37 for optimum yields on a rotary shaker at 250 rpm . at every 24 h interval ,
the flasks were harvested and antimicrobial metabolites production determined in terms of their antimicrobial spectrum .
the concentrates were tested for antibacterial activity by disc diffusion method ( bauer et al . , 1966 ) against b. subtilis for 15 consecutive days .
the effect of ph and temperature on the antimicrobial production by the strain was studied by inoculating 24 h old culture in czapek - dox ( alkaline ) broth .
the ph of the media was adjusted using hydrochloric acid ( 1 m ) and sodium hydroxide ( 1 m ) . for temperature study , after sterilizing and inoculating with spores the flask were incubated at different temperatures ( 25~45 ) .
the production of antimicrobial metabolites was tested for antimicrobial activity after 120 h of incubation by disc diffusion method against b. subtilis . to determine the effect of carbon sources on antimicrobial metabolites production , different carbon sources such as sucrose , d - glucose , d - fructose , mannitol , d-(+ ) galactose , xylosa , lactose , d ( + ) mannose , rhamnose and maltose were added to the basal medium containing kcl ( 0.05% ) , kh2po4 ( 0.1% ) , mgso4 , 7h2o ( 0.05% ) and feso4 , 7h2o ( 0.001% ) .
carbon sources were added in 3% concentration to the basal medium supplemented with nano3 ( 0.2% ) as nitrogen source .
the effect of various nitrogen sources such as nano3 , yeast extract , kno3 , ammonium sulphate , ammonium chloride , peptone , casein , l - asparagine and beef extract was studied by adding nitrogen source ( 0.2% ) to the basal medium containing glucose ( 3% ) .
final ph of the medium adjusted to 8 and antibacterial activity was checked by disc diffusion method against b. subtilis for 15 consecutive days .
salt concentration has a profound effect on the production of antibiotic from microorganism due to its effect on the osmotic pressure to the medium ( pelczer et al . , 1993 ) .
to observe this effect nacl was added to culture media at different concentrations such as 0% , 0.5% , 1% , 2% , 3% , 4% and 5% respectively .
glucose ( 3% ) and yeast extract ( 0.2% ) was used as carbon and nitrogen source respectively .
the organism was isolated from a soil sample collected from rajshahi , bangladesh at the depth of 0.75 m using crowded plate technique ( hammond and lambert , 1978 ) .
the organism was identified as a novel , streptomyces species on the basis of morphological , physiological , biochemical ( shirling and gottlieb , 1969 ) and 16s rdna studies ( genbank accession number bankit1256035 gq500975 ) and designated as streptomyces sp .
pure culture of the strain was maintained on czapek dox ( alkaline ) agar slant .
shake flask fermentations were run in 500 ml flasks containing 100 ml czapek - dox ( alkaline ) broth .
the flasks were allowed to cool and the liquid media inoculated with spores of the organisms from previously prepared agar slant were poured into it
. then they were incubated at 37 for optimum yields on a rotary shaker at 250 rpm . at every 24 h interval ,
the flasks were harvested and antimicrobial metabolites production determined in terms of their antimicrobial spectrum .
the concentrates were tested for antibacterial activity by disc diffusion method ( bauer et al . , 1966 ) against b. subtilis for 15 consecutive days .
the effect of ph and temperature on the antimicrobial production by the strain was studied by inoculating 24 h old culture in czapek - dox ( alkaline ) broth .
the ph of the media was adjusted using hydrochloric acid ( 1 m ) and sodium hydroxide ( 1 m ) . for temperature study , after sterilizing and inoculating with spores the flask were incubated at different temperatures ( 25~45 ) .
the production of antimicrobial metabolites was tested for antimicrobial activity after 120 h of incubation by disc diffusion method against b. subtilis .
to determine the effect of carbon sources on antimicrobial metabolites production , different carbon sources such as sucrose , d - glucose , d - fructose , mannitol , d-(+ ) galactose , xylosa , lactose , d ( + ) mannose , rhamnose and maltose were added to the basal medium containing kcl ( 0.05% ) , kh2po4 ( 0.1% ) , mgso4 , 7h2o ( 0.05% ) and feso4 , 7h2o ( 0.001% ) .
carbon sources were added in 3% concentration to the basal medium supplemented with nano3 ( 0.2% ) as nitrogen source .
the effect of various nitrogen sources such as nano3 , yeast extract , kno3 , ammonium sulphate , ammonium chloride , peptone , casein , l - asparagine and beef extract was studied by adding nitrogen source ( 0.2% ) to the basal medium containing glucose ( 3% ) .
final ph of the medium adjusted to 8 and antibacterial activity was checked by disc diffusion method against b. subtilis for 15 consecutive days .
salt concentration has a profound effect on the production of antibiotic from microorganism due to its effect on the osmotic pressure to the medium ( pelczer et al . , 1993 ) .
to observe this effect nacl was added to culture media at different concentrations such as 0% , 0.5% , 1% , 2% , 3% , 4% and 5% respectively .
glucose ( 3% ) and yeast extract ( 0.2% ) was used as carbon and nitrogen source respectively .
the production of antimicrobial metabolites at different days was determined by disc diffusion assay method measuring the zone of inhibition against b. subtilis .
the highest level was obtained after 10 days of incubation and then production was declined gradually ( fig .
1 ) . thus the organism was allowed to incubate for 10 days for the production of antimicrobial metabolites .
the effect of ph and temperature on antimicrobial metabolites production by the strain is presented in fig . 2 and 3 .
the organism produced high levels of antibiotic production when culture medium incubated at 39. therefore the strain was strictly mesophilic for secondary metabolites production .
extreme ph and temperature were unfavorable for antibiotic production ( fig . 2 and 3 ) .
the effect of different carbon sources on antibiotic production by the strain is presented in fig .
4 . among the carbon sources , glucose proved to be the best carbon source for both cell growth as well as antimicrobial metabolites production by the strain .
sucrose also gave a similar pattern result followed by mannose , fructose , mannitol , rhamnose and xylose respectively .
no antibiotic was produced when the medium was supplemented with galactose , lactose , raffinose and maltose as a sole carbon source .
carbohydrates such as glycerol , maltose , lactose and some others are known to have interference with the production of secondary metabolites ( demain and fang , 1995 ) . in the present study , the strain was found to produce high levels of antimicrobial metabolites in the medium supplemented with glucose ( 2% ) as sole carbon source . in case of streptomyces species , with regards to carbon sources
species specific variation may occur for cell growth and secondary metabolites production ( jonsbu et al . , 2002 ) .
medium supplemented with nano3 and peptone gave similar results followed by kno3 , beef extract , casine , l - asparazine , ammonium sulphate and ammonium chloride .
it was observed that the production of antimicrobial metabolites was maximum in presence of 1% nacl .
6 . among different minerals tested only k2hpo4 and mgso47h2o had positive effects on antibiotic production followed by nacl , kcl and kh2po4
 an actinomycete strain was isolated from northern part of bangladesh and identified as a new streptomyces species on the basis of its morphological , biochemical , cultural characteristics and 16s rrna data . 
 attempts were made to optimize the culture conditions for the production of antimicrobial metabolites by this strain . 
 antimicrobial metabolites production was started after 7 days of incubation of culture broth and reached its maximum levels after 10 days and thereafter gradually decreased . 
 the maximum production of antimicrobial metabolites was obtained when the culture medium ph was adjusted to 8 . 
 the optimum temperature for antimicrobial metabolites production was 39 , indicated the new strain as mesophilic organism . 
 basel medium supplemented with glucose and yeast extract as carbon and nitrogen sources , respectively , was proved to be the best for the production of bioactive metabolites . 
 maximum production of bioactive metabolites was when nacl concentration was 1% and among different minerals tested , k2hpo4 and nacl showed positive influence on antibiotic production by the strain . 