Production and characterization of insoluble alpha-1,3-linked glucan and soluble alpha-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 alpha-glucans. By regulation of pH above 5.5, soluble alpha-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 alpha-glucan, was also increased. Then, alpha-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 a-glucan is a highly linear dextran with alpha-1,6 glycosidic bonds while the insoluble alpha-glucan has 93% of alpha-1,3 and 7% of alpha-1,6 glycosidic bond. The results extend our understanding of exopolysaccharides production by L. pseudomesenteroides, and this water insoluble alpha-1,3-glucan might have potential application as biomaterials and/or biochemicals. (C) 2021 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.