EFFECTS OF CULTURE MEDIUM COMPOSITION ON BIOSYNTHESIS OF EXOPOLYSACCHARIDES

摘要

The study investigated the influence of culture medium composition on the amount and structure of exopolysaccharides produced by the fermentation of lactic acid bacteria. It was established that the most favorable culture medium composition was the standard MRS prepared in milk supplemented with sucrose. Dynamic conditions were found more suitable for the biosynthesis of exopolysaccharides. An amount of 9 g dry polymer/L of culture medium was obtained. Gel permeation chromatography highlighted the presence of multiple exopolysaccharide fractions, mainly with a low degree of heterogeneity. FTIR, H-1 and C-13-NMR analyses showed that dextran was the main biosynthesis product. The thermal stability of the obtained biopolymers was determined by TGA and DSC analyses. Both methods indicated a pure and stable polymer, comparable with dextran.