advantages of the present invention will become more apparent from the detailed description given hereinafter . however , it should be understood that the detailed description and specific examples , while indicating preferred embodiments of the invention , are given by way of illustration only , since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description . commercialized stevia extract ( lanzhou julong high - tech food industry co ., ltd , china ), containing stevioside ( 38 - 40 %), rebaudioside a ( 41 - 42 %), rebaudioside c ( 7 - 8 %), and dulcoside ( 1 - 1 . 5 %), with total content of 90 %, was dissolved in distilled water to prepare a 5 - 10 %, more preferably 7 - 8 % solution . then , the ph was adjusted to 9 . 5 - 10 . 0 by calcium hydroxide or any other suitable basic material such as calcium carbonate . after mixing at 45 - 50 ° c . for 20 - 30 min , the solution was cooled to ambient temperature and was neutralized by fecl 3 . after mixing for 20 - 30 min the precipitate was removed by filtration and the filtrate was deionized and decolorized by amberlite fpc23h , amberlite fpa51 , and amberlite fpa98cl in a conventional manner . the clear solution was passed through polysulfone - based ultrafiltration membranes with a filtering discrimination of 2 . 5 kda ( liumar technologies , ottawa , canada ) with diafiltration , concentrated under vacuum and spray dried . however , the invention is not restricted to polysulfone membranes , and any suitable type of membrane can be used . any type of existing stevia extract with various ratios of sweet glycosides can be used . a white powder with content of stevioside , rebaudioside a , rebaudioside c , and dulcoside more than 98 % was obtained ( fig1 ). the hplc analysis of the obtained product was performed using an agilent technologies 1100 series ( usa ) equipped with a zorbax - nh 2 column using an acetonitrile - water gradient from 80 : 20 , v / v ( 2 minutes ) to 50 : 50 , v / v during 70 minutes and uv detector at 210 nm . the enzymatic transglucosylation of sweeteners obtained was developed with cgtases produced by bacillus stearothermophilus vrpm b - 4905 ( russian national collection of industrial microorganisms ). in this step , any cgtase possessing a intermolecular transglucosylation activity can by applied . the cultivation of b . stearothermophilus was conducted under aerobic conditions at 56 ° c . at a ph range of 5 - 8 , preferably 6 . 8 - 7 . 2 . the cultivation time was 20 - 22 hours . the aeration rate was adjusted in the range of 0 . 5 : 1 . 0 v / v per one minute , preferably , 1 : 1 v / v . the cultivation can be carried out in a batch or continuous conditions . any synthetic and natural nutrient culture media can be used for the cultivation of the microorganisms . any carbon - containing substances can be used in the invention as carbon sources . for instance , saccharides such as sucrose , maltose , dextrin , glucose , lactose , galactose , cyclodextrins , and starch , as well as saccharide - containing products such as molasses and yeast extracts , can be used as the carbon sources . the concentrations of these carbon sources in nutrient culture media are selectively chosen depending on their types . however , the best results are obtained in the case of 0 . 5 - 2 . 0 % of starch , preferably , 0 . 7 - 0 . 9 %. the nitrogen sources usable in the invention are , for example , inorganic nitrogen - containing compounds such as ammonium salts ; and organic nitrogen - containing compounds such as urea , corn steep liquor , casein , peptone , yeast extract , and beef extract . the inorganic ingredients usable in the present invention are , for example , calcium salts , magnesium salts , potassium salts , sodium salts , phosphates and others . since the cgtase activity was found in the cell - free nutrient media , the media can be collected and used as a crude enzyme . conventional liquid - solid separation methods can be used to remove cells . for example , methods to directly centrifuge the culture and those to filtrate with pre - coat filters or to separate cells by membrane filtration using plain filters or hollow - fibers . the resulting cell - free culture broth can be used intact as a crude enzyme , and preferably , used after concentration . the concentration methods usable in the present invention are , for example , salting out using ammonium sulfate , sedimentation using acetone and / or alcohol , and concentration using ultrafiltration membranes such as plain filters and hollow - fibers . however , any suitable collection and concentration methods can be used . crude enzymes can be immobilized by conventional methods such as adsorption , covalent biding , and entrapping . crude enzymes can be used intact or after purification . for example , cell - free culture broth was concentrated using ultrafiltration membranes , and purified successively on beta - cyclodextrin polymers to obtain an enzyme preparation exhibiting an electrophoretically single protein band . the activity of cgtases according to the invention was determined by the following assay : the mixture of 10 μl enzyme and 0 . 2 % amylose solution in 0 . 2m buffer was incubated at 50 ° c . for 10 min . the reaction was stopped by adding 1 ml 0 . 5m acetic acid and 0 . 5 ml 0 . 02 % i 2 / 0 . 2 % ki solution . the mixture volume was brought up to 10 ml with distilled water , and extinction was determined under 700 nm . the enzyme activity unit was accepted as the enzyme quantity that has reduced the intensity of blue color by 10 % for 1 min . starches of various origins , for example , from wheat , corn , potato , tapioca , and sago can be used as donors for glucosyl units . the dextrose equivalent of the partially hydrolyzed starch can be in the range of 10 - 25 , preferably 12 - 16 . the amount of enzyme to be used for liquefaction of starch was within the limits of 1 - 5 units / gram of starch , preferably 2 - 3 units . in the stage of transglucosylation the quantity of enzyme was 7 - 15 units / gram of starch , preferably 8 - 11 units . however , the larger amount of enzyme raises the yield of transglucosylated products and shortens the duration of enzymatic reaction . the process temperature was 65 - 75 ° c ., preferably 68 - 72 ° c . increasing the reaction temperature increases the reaction rate . low temperatures are not favorable . after about 12 - 13 hours of reaction between glycosides and starch , the remaining maltooligosaccharides are transformed into the fructose - terminated oligosaccharides ( fto ) by adding to the reaction mixture the sucrose in an amount of 50 - 100 %, preferably 50 - 70 % from the content of maltooligosaccharides . then , the reaction was continued for another 5 - 6 hours at the same temperature . the ftos are less prone to fermentation and acid production by streptococcus mutans , which are usually abundant in oral cavity , in contrast to traditional sugars used in food products , which are digested with forming acids and insoluble glucans and thus give rise to various forms of caries . the reaction was stopped by heating at 95 ° c . for 15 minutes to inactivate the enzyme , and the solution was decolorized with a small amount of activated carbon and then desalted by passage through ion exchange resins , such as amberlite fpc23 ( h type ) and amberlite fpa51 ( oh type ), concentrated and dried . the resulting product ( sample no . 2 ) contains non - modified glycosides , their glycosylated derivatives and a mixture of fructose - terminated oligosaccharides . sample no . 1 , which along with glycosides , contains about 17 - 20 % of various maltooligosaccharides , was obtained without using sucrose . other appropriate decolorizing and desalting methods can be used . in order to prepare a sweetener with higher content of total sweet glycosides only ( the sum of glycosylated and non - glycosylated glycosides ), the malto - or fructose - terminated oligosaccharides were removed from the reaction mixture using amberlite xad16 hp or dowex 50w - x4 ( ca 2 + ), and the solution of glycosides are powdered by spray drying ( sample no . 3 and sample no . 4 , respectively ) ( fig2 ). the typical hplc chart of fructose terminated oligosaccharides is presented in the fig3 ). the composition of the samples obtained is summarized in the table 1 . based on the results of preliminary test on the sweetening power of the sweeteners , an aqueous solutions were prepared that exhibited a sweetness comparable to that of 10 % aqueous sucrose solution . the organoleptic test was carried out at 25 ° c ., with 20 panel members , and , by the panel , the most desirable and most undesirable sweeteners were chosen along with comments on their taste qualities . as the control the usual type of glycosylated stevioside was prepared . the results are shown in table 1 . as apparent from the results in table 2 , sweetness quality of the samples no . 2 , no . 3 , and no . 4 was rated as most superior . the further purified sweetener , with low content of intact stevioside ( sample no . 4 ), was observed as being slightly superior to samples no . 2 and no . 3 . the sweeteners can be used for seasoning of various food products ( for example , soy sauce , soy sauce powder , soy paste , soy paste powder , dressings , mayonnaise , vinegar , powder vinegar , bakery products and confectioneries , frozen - desserts , meat products , fish - meat products , potato salad ; bottled and canned foods , fruits and vegetables ) in intact or mixed forms with other sweeteners , such as corn syrup , glucose , maltose , sucrose , lactose , aspartame , saccharin , sugar alcohols , organic and amino acids , flavors and / or coloring agents . the products are favorably usable as a low - cariogenic and low - calorie sweetener because it is less fermentable by oral dental - caries causative microorganisms ; for example , low - cariogenic food products , such as confectioneries including chewing gum , chocolate , biscuits , cookies , toffee and candy ; and soft drinks such as coffee , cocoa , juice , carbonated drinks , sour milk beverage , and yogurt drinks ; alcoholic drinks , such as brandy , whisky , vodka and wine . in addition to the above - described uses , the sweeteners are usable for sweetening drugs and cosmetics . a strain of bacillus stearothermophilus vkpm b - 4905 was inoculated on 10 liters of a sterilized culture medium ( ph 7 . 0 - 7 . 2 ) containing 0 . 7 % ( w / v ) soluble starch , 0 . 5 % ( w / v ) corn steep liquor , 0 . 53 % ( w / v ) ammonium chloride , and 0 . 2 % ( w / v ) calcium carbonate . the mixture was incubated at a temperature of 56 ° c . for 20 hours with aeration and stirring . the resultant culture broth was centrifuged , and the supernatant was concentrated up to five times on ultrafiltration membranes . the concentrated solution was diluted with three volumes of distilled water and again concentrated to the initial concentrate volume . the process was repeated for three times . a crude enzyme preparation with an activity of about 90 , 000 units was obtained . 150 grams of commercialized stevia extract ( ganzhou julong high - tech food industry co ., ltd , china ), containing stevioside ( 40 %), rebaudioside a ( 42 %), rebaudioside c ( 7 %), and dulcoside a ( 1 %), with total content of 90 %, were dissolved in 2000 ml of distilled water . after complete dissolving the ph of the solution was adjusted to 9 . 5 by about 3 grams of calcium hydroxide and maintained with slow agitation for 30 minutes at 50 ° c . then , the suspension was cooled to ambient temperature , neutralized with about 6 grams of fecl 3 and agitation was continued for another 30 minutes . the precipitate formed was removed by filtration , and the filtrate was deionized and decolorized by amberlite fpc23h , amberlite fpa51 , and amberlite fpa98cl in the conventional manner . the clear solution was passed through polysulfone based ultrafiltration membranes with a filtering discrimination of 2 . 5 kda ( liumar technologies , ottawa , canada ) with diafiltration , concentrated under vacuum and spray dried . 135 grams of purified extract was obtained with 98 . 2 % of total content of glycosides . 100 grams of tapioca starch was suspended in 600 ml of distilled water ( ph 6 . 5 - 7 . 0 ), 200 units of cgtase obtained in example 1 was added , and the liquefaction of starch was carried out at 75 - 80 ° c . for about one hour to dextrose equivalent about 15 . after cooling to 70 ° c ., the purified stevia extract in an amount of 100 grams was added and mixed until a homogeneous solution was obtained . 800 units of cgtase was added to the solution and allowed to incubate at a temperature of 70 ° c . for 18 hours . at 55 ° c . and 60 ° c . the reaction time was 48 hours and 32 hours , respectively . at 75 ° c . the reaction was completed in 12 - 13 hours . the obtained reaction mixture was heated at 95 ° c . for 15 minutes to inactivate the enzyme , decolorized with 0 . 2 % ( w / v ) of activated carbon , and desalted by passage through ion exchange resins amberlite fpc23h ( h type ) and amberlite fpa51 ( oh type ). the solution was concentrated at 65 ° c . under reduced pressure , and dried into a powder form . 196 grams of product were obtained ( corresponds to sample no . 1 ). the reaction between purified stevia extract and starch was carried out according to the procedure of example 2 . after 12 hours , 20 grams of sucrose were added to reaction mixture and transformation was continued at 70 ° c . for another 5 hours . the obtained reaction mixture was treated similar to sample 1 . 217 grams of product were obtained ( corresponds to sample no . 2 ). 10 grams of sample 2 , prepared according to the example 3 , were dissolved in the 20 ml of distilled water and at ambient temperature was passed through a column packed with amberlite xad16 hp ( 5 . 0 × 50 cm ) with spacial velocity of 0 . 2 hour − 1 . the column was washed sequentially with water ( 1000 ml ), 20 % ethanol ( 1000 ml ), 50 % ethanol ( 1000 ml ), and 70 % ethanol ( 1000 ml ). the water fraction contained mainly monosaccharides , while 20 % ethanol fraction comprised oligosaccharides . in 50 % ethanol mainly glycosylated products were detected . non - modified forms of glycosides with a small amount of glycosylated derivatives were eluted by 70 % ethanol . the 50 % and 70 % ethanol fractions were combined , concentrated and dried into powder form . 6 . 2 grams of product were obtained ( sample no . 3 ). 10 grams of sample 2 , prepared according to example 3 , were dissolved in the 20 ml of distilled water and at ambient temperature was passed through the column packed with dowex 50w - x4 ( ca 2 + ) ( 5 . 0 × 50 cm ). the elution was performed using distilled water with spacial velocity of 0 . 3 hour − 1 . the main fractions containing glycosylated derivatives of sweet glycosides were combined , concentrated , and dried into powder form . 5 . 8 grams of product were obtained ( sample no . 4 ). a composition containing 30 kg of cacao liquor , 11 . 5 kg of cacao butter , 14 kg of milk powder , 44 kg of sorbitol , 0 . 1 kg of salt , and 0 . 1 kg of sweetener , obtained according to the examples 2 , 3 , 4 , or 5 , was kneaded sufficiently , and the mixture was then placed in a refiner to reduce its particle size for 24 hours . thereafter , the content was transferred into a conche , 300 grams of lecithin was added , and the composition was kneaded at 50 ° c . for 48 hours . then , the content was placed in a shaping apparatus , and solidified . the products were low - cariogenic and low - calorie chocolate with excellent texture . however , the organoleptic test carried out with 20 panelists , revealed the no lingering after - taste for the chocolate prepared using sweetener of sample no . 1 . the most desirable one was the product with sample no . 4 ( 8 members ), sample no . 2 ( 7 members ), and sample no . 3 ( 5 members ). 1 . 50 kg of whole milk were heated to 45 ° c ., and 300 grams of milk cream , 100 grams of tagatose , 90 grams of sorbitol , 6 grams of carrageenan as a stabilizer , 3 grams of polysorbate - 80 as an emulsifier , and 1 . 0 gram of sweetener , obtained according to the examples 2 , 3 , 4 , or 5 , were added into the milk and was stirred until the ingredients completely dissolved . the mixture then was pasteurized at a temperature of 80 ° c . for 25 seconds . the homogenization of the obtained mixture was carried out at a pressure of 800 bars and the samples were kept at a temperature of 4 ° c . for 24 hours to complete the aging process . vanilla flavor ( 1 . 0 % of the mixture weight ) and coloring ( 0 . 025 % of the mixture weight ) are added into the mixture after the aging process . the mixture was then transferred to ice cream maker to produce ice cream automatically . samples of ice creams produced were transferred to sealed containers and were kept in the freezer at a temperature of − 18 ° c . the application of sweeteners does not affect the physicochemical properties of ice cream , as well as the overall attributes of color , smoothness , surface texture , air cell , vanilla aroma intensity , vanilla taste , chalkiness , iciness and melting rate . an organoleptic test carried out with 20 panelists . the most desirable one was the product with sample no . 4 ( 8 members ), sample no . 2 ( 6 members ), and sample no . 3 ( 6 members ). orange concentrate ( 35 %), citric acid ( 0 . 38 %), ascorbic acid ( 0 . 05 %), sodium benzoate ( 0 . 02 %); orange red color ( 0 . 01 %), orange flavor ( 0 . 20 %), and a sweetener ( 0 . 06 %), obtained according to the examples 2 , 3 , 4 , or 5 were blended and dissolved completely in water ( up to 100 %) and pasteurized . the sensory evaluations of the samples are summarized in the table 3 . the data shows that best results can be obtained using of high purity sweeteners . 1 kg of flour , 37 . 38 grams of fructooligosaccharide syrup , 80 grams of margarine , 20 grams of salt , 20 grams of yeast , and 0 . 25 grams of sweetener , obtained according to the examples 2 , 3 , 4 , or 5 were placed into a blender and mixed well . 600 nil of water were poured into the mixture and kneaded sufficiently . at the completion of the kneading process , the dough has taken to be shaped and raised for 30 to 45 minutes . the ready dough was put into oven and baked for 45 minutes . bread samples were in creamy white in color , with a smooth texture . they displayed similar properties and taste . flour ( 50 . 0 %), margarine ( 30 . 0 %) fructose ( 10 . 0 %), maltitol ( 8 . 0 %), whole milk ( 1 . 0 %), salt ( 0 . 2 %), baking powder ( 0 . 15 %), vanillin ( 0 . 1 %) and sweetener obtained according to the examples 2 , 3 , 4 or 5 ( 1 . 0 %) were kneaded well in dough - mixing machine . after molding of the dough the cookies were baked at 200 ° c . for 15 minutes . the product is a low - calorie diet cookie with excellent properties and appropriate sweetness . in 5 kg of defatted milk 4 . 0 grams of sweetener , prepared according to examples 2 , 3 , 4 or 5 , were dissolved , and after pasteurizing at 82 ° c . for 20 minutes , the milk was cooled to 40 ° c . a starter in amount of 150 grams was added and the mixture was incubated at 37 ° c . for 6 hours . then , the fermented mass was maintained at 10 - 15 ° c . for 12 hours . the product is a low - calorie and low - cariogenic yoghurt without foreign taste and odor . a mixture containing 58 . 5 % lactose , 10 % calcium silicate , 5 % cross - carmellose , 5 % l - leucine , 1 % aerosol 200 , 0 . 5 % magnesium stearate , and 20 % of a sweetener obtained according to the examples 2 , 3 , 4 , or 5 , was kneaded sufficiently . then the mixture was shaped with the use of a tabletting machine , equipped with punchers of 6 . 2 mm diameter , into tablets of 70 mg each , 3 . 0 mm thick , and 10 ± 1 kg hardness the tablets can be easily administrated due to their appropriate sweetness . however , the formulations using sample no . 1 and sample no . 2 were somewhat sticky with a solubility of about 3 - 4 minutes in water at 25 ° c . the tablets , prepared with sample no . 3 and no . 4 , show the best characteristics with the solubility at around 20 - 30 seconds . a toothpaste was prepared by kneading a composition formulated from calcium phosphate , ( 45 . 0 %), carboxymethylcellulose ( 1 . 5 %), carrageenan ( 0 . 5 %), glycerol ( 18 . 0 %), polyoxyethylene sorbitan mono - ester ( 2 . 0 %), beta - cyclodextrin ( 1 . 5 %), sodium laurylsarcosinate ( 0 . 2 %), flavoring ( 1 . 0 %), preservative ( 0 . 1 %), a sweetener obtained similarly as in examples 2 , 3 , 4 or 5 ( 0 . 2 %) and water to 100 %, were blended in the usual way . it is to be understood that the foregoing descriptions and specific embodiments shown herein are merely illustrative of the best mode of the invention and the principles thereof , and that modifications and additions may be easily made by those skilled in the art without departing for the spirit and scope of the invention , which is therefore understood to be limited only by the scope of the appended claims .