Efficient production, structural characterization and bioactivity of an extracellular polysaccharide from Grifola frondosa endophytic Burkholderia sp.

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Citation abstract

Endophytic bacteria Burkholderia sp. (GFB) was firstly identified and isolated from Grifola frondosa. An exopolysaccharide (GFB-MP) of GFB strain was obtained following fermentation optimization, resulting in a maximum yield of 11.36 g/L in 5 L fed-batch fermentation. GFB-MP (M W 432.05 kDa) comprised mainly galactose, glucose, and mannose with a ratio of 39.52:14.22:46.26, indicating a mannose-enriched polysaccharide. Methylation and NMR analysis revealed that GFB-MP consisted of the main chain that was repeat units →4)-α-D-Glcp-(1 → bonded →6)-β-D-Galp-1 → repeat units and three O-6-linked branched chains. Antibacterial activity suggested that GFB-MP can effectively inhibit food pathogen bacteria Listeria and Escherichia coli with inhibition ratios of 73.4 % and 81.6 %, respectively. In addition, GFB-MP exhibited remarkable growth-promoting activity on probiotics with >50 % increments of cell growth. This study demonstrates that GFB-MP has the potential for health-beneficial food. Knowledge of endophyte polysaccharides in G. frondosa is important to understand their physiological activities and symbiotic interactions.