Physiological studies of Leuconostoc mesenteroides strain NRRL B-1149 during cultivation on glucose and fructose media

Glycosyltransferases are extracellular and cell-associated sucrase enzymes produced mainly by lactic acid bacteria Leuconostoc mesenteroides, oral Streptococcus species and also Lactobacillus species. According to the synthesized polymer (glucan or fructan) in the presence of sucrose, these enzymes are divided into two groups: glucosyltransferases (GTFs) and fructosyltransferases (FTFs). Only Streptococcus, Lactobacillus and Leuconostoc strains are known as producers of both GTFs and FTFs. The enzymes from Lactobacillus and Leuconostoc spp. are implicated in the synthesis of polymers and oligosaccharides (OS) important for human health because of their prebiotic properties and immunomodulating activity. In the present work, we studied the production of extracellular and cell-associated glycosyltransferases by Leuconostoc mesenteroides strain NRRL B-1149 during its growth on media containing glucose or fructose as a main carbon source. The enzyme activities, pH and biomass formation were measured and compared during the cultivation. We have shown that glucose and fructose have not an equal role for enzyme production. The highest extracellular activity was detected at the 4th hour during the cultivation of the strain in medium with fructose – 5.45 U/mg. When the strain was cultivated in medium with glucose, the maximum of extracellular enzyme activity was detected at the 5th hour of the cultivation but the measured activity was about 9 times lower compared to these, obtained after cultivation in fructose medium. The studied strain produced mainly extracellular glycosyltransferases in glucose or fructose medium, which were 92.4% and 97.1% of the total enzyme activity, respectively. In order to characterize the produced enzymes, cell-associated and extracellular enzymes were determined using SDS-PAGE and in situ Periodic Acid Schiff′s staining after incubation with 10% sucrose. When the investigated strain was grown in media with sucrose, glucose or fructose, several types of glycosyltransferases were detected – dextransucrase with molecular weight 180 kDa and two fructosyltransferases, corresponding to 120 kDa and 86 kDa molecular weights.