Effect of sodium and calcium on polysaccharide production and the activities of enzymes involved in the polysaccharide synthesis of Lentinus edodes

Lentinan is a Lentinus edodes secondary metabolite that can regulate human immune function, but yields are low. Here, the effects of Ca2+ and Na+ on L. edodes lentinan content were investigated. Metal ion concentrations and induction times were optimized according to mycelial biomass, and intracellular polysaccharide (IPS), extracellular polysaccharide (EPS), and total polysaccharide (TPS) content. The activities and gene expression of phospho-glucose isomerase (PGI), phosphoglucomutase (PGM), and UDP-glcpyrophosphorylase (UGP) were also measured. Ca2+ and Na+ concentration and induction time affected biomass, IPS, and EPS concentrations. Na+ increased EPS, IPS and TPS, while Ca2+ increased biomass, IPS, and TPS. During fermentation, mycelial biomass varied greatly under Ca2+ induction, while IPS, EPS and TPS varied greatly under Na+ induction. PGM and UGP activities increased in the presence of Na+, while PGI increased with Ca2+. Compared to control samples, pgi and pgm expression under Na+ was greater at days 45 and 60, respectively, while under Ca2+, ugp expression was greater at day 45. IPS content correlated significantly with enzyme activity, while EPS correlated with PGM activity. Our data contributes to better understanding how Na+ and Ca2+ affect mycelial growth and secondary metabolite production, and of polysaccharide biosynthesis mechanisms of L. edodes.