We studied the effect of polysaccharides: native and soluble potato starch, amylopectin, amylose, dextrin and maltodextrin, disugars ? maltose, saccharose and lactose, and of simple sugars ? glucose, mannose and xylose on intensity of biosynthesis of amylases, being expressed as an activity of alpha-amylase and glucoamylase, contained in the liquid after cultivation of bacteria strains: Lactobacillus plantarum K, Lactobacillus plantarum C and Lactobacillus amylovorus. It was found that native and soluble potato starch, being used as the only source of carbon in culture medium, stimulated the process of amylases biosynthesis by the examined bacterial strains. The highest level of alpha-amylase activity, equal to 13-14 JA and of glucoamylase ? 0,37-0,39 JGA in 1 ml of post-cultivation liquid was obtained after 72 h of cultivation of Lactobacillus plantarum K and Lactobacillus plantarum C when the native potato starch was the only source of carbon in medium. Lactobacillus amylovorus strain synthetised amylases with the highest level of alpha-amylase activity, amounting to 17 JA and glucoamylase ? 0,24 JGA/ml of post-cultivation liquid, after 72 h of cultivation when the potato starch was the only carbon source in the medium. On the other hand, when the native potato starch was used, the activity of alpha-amylase was equal to 9 JA and that of glucoamylase 0,09 JGA in 1 ml of post-cultivation liquid. The amylolytic activity in post-cultivation liquids was increased to smaller extent when the carbon source in culture of the examined bacterial strains was dextrin, maltodextrin, saccharose, maltose or mannose.