ANALYSIS OF THE EXOPOLYSACCHARIDES PRODUCED BY LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS NCFB-2772 GROWN IN CONTINUOUS-CULTURE ON GLUCOSE AND FRUCTOSE

The exopolysaccharides produced by Lactobacillus delbrueckii subsp, bu lgaricus NCFB 2772 grown in defined medium were investigated, At equal cell densities, the strain produced 95 mg l(-1) exopolysaccharides wi th glucose and 30 mg l(-1) with fructose as the carbohydrate source. H igh-performance size-exclusion chromatography of the exopolysaccharide s produced on glucose showed the presence of two fractions with relati ve molecular masses (M-r) of 1.7 x 10(6) and 4 x 10(4) in almost equal amounts, The exopolysaccharides produced on fructose contained mainly a fraction of low M-r of 4 x 10(4). The high-M-r fraction of the puri fied exopolysaccharides produced on glucose appeared to have a sugar c omposition of galactose, glucose and rhamnose in the molar ratio of 5: 1:1, whereas the low-M-r weight fraction contained galactose, glucose and rhamnose in the molar ratio of approximately 11:1:0.3. The purifie d exopolysaccharide fractions produced on fructose showed comparable r atios, The high-molecular-mass fractions contained terminally linked g alactose, 1,2,3-linked galactose, 1,3,3-linked galactose, 1,3-linked g lucose and terminally linked rhamnose, The low-molecular-mass fraction s contained mainly 1,3-linked galactose and 1,6-linked galactose and l ower amounts of other sugar linkages, The production of the high-M-r f ractions appeared to be dependent on the carbohydrate source, whereas the low-M-r fractions were produced more continuously.