Glucansucrases produced by fructophilic lactic acid bacteria Lactobacillus kunkeei H3 and H25 isolated from honeybees

Twenty fructophilic isolates from the stomachs of honeybee Apis mellifera ligustica from the region of Plovdiv, Bulgaria were obtained. Fructophilic isolates H3 and H25 showed formation of mucous colonies during cultivation on medium with sucrose, suggesting exopolysaccharide synthesis. The sequencing analysis of 16S rRNA identified isolates H3 and H25 as fructophilic lactic acid bacteria Lactobacillus kunkeei. The in situ analysis and periodic acid-Schiff's staining, showed that Lb. kunkeei H3 and H25 produce extracellular glucansucrases with molecular weight of about 300 kDa. In the cell-associated fractions, additional glucansucrase is detected with molecular weight of about 180 kDa. The content of α-(1 → 6) linkages in the glucans synthesized with extracellular glucansucrases from H3 and H25 after dextranase hydrolysis was significantly lower than this one of the classical dextran - about 35 and 62%, respectively. These results suggest a more branched structure of the studied polymers.