Exopolysaccharides produced by lactic acid bacteria of kefir grains.

A Lactobacillus delbrueckii subsp. bulgaricus HP1 strain with high exopolysaccharide activity was selected from among 40 strains of lactic acid bacteria, isolated from kefir grains. By associating the Lactobacillus delbrueckii subsp. bulgaricus HP1 strain with Streptococcus thermophilus T15, Lactococcus lactis subsp. lactis C15, Lactobacillus helveticus MP12, and Sacharomyces cerevisiae A13, a kefir starter was formed. The associated cultivation of the lactobacteria and yeast had a positive effect on the exopolysaccharide activity of Lactobacillus delbrueckii subsp. bulgaricus HP1. The maximum exopolysaccharide concentration of the starter culture exceeded the one by the Lactobacillus delbrueckii subsp. bulgaricus HP1 monoculture by approximately 1.7 times, and the time needed to reach the maximum concentration (824.3 mg exopolysacharides/l) was shortened by 6 h. The monomer composition of the exopolysaccharides from the kefir starter culture was represented by glucose and galactose in a 1.0:0.94 ratio, which proves that the polymer synthesized is kefiran.