Production and characterization of insoluble α-1,3-linked glucan and soluble α-1,6-linked dextran from Leuconostoc pseudomesenteroides G29

Exopolysaccharides can be produced by various bacteria and have important biological roles in bacterial survival depend on molecular weight, linkage, and conformation. In this study, Leuconostoc pseudomesenteroides G29 was identified and found to produce two types of exopolysaccharides from sucrose including soluble and insoluble α-glucans. By regulation of pH above 5.5, soluble α-glucan production was increased to 38.4 g∙L⁻¹ from 101.4 g∙L⁻¹ sucrose with fewer accumulation of lactic acid and acetic acid. Simultaneously, the quantity of thick white precipitate, that is insoluble α-glucan, was also increased. Then, α-glucans were prepared by enzymatic reaction with crude glucansucrases from the supernatant of G29 fermentation broth and purified for structure analysis. Based on the integration analysis of FT-IR and NMR, it was observed that soluble α-glucan is a highly linear dextran with α-1,6 glycosidic bonds while the insoluble α-glucan has 93% of α-1,3 and 7% of α-1,6 glycosidic bond. The results extend our understanding of exopolysaccharides production by L. pseudomesenteroides, and this water insoluble α-1,3-glucan might have potential application as biomaterials and/or biochemicals.