Functions of the cell wall polysaccharide schizophyllan during vegetative growth of Schizophyllum commune

Abstract

Schizophyllan, a β-(1,3)(1,6)-glucan, is part of the cell wall of the mushroom-forming fungus Schizophyllum commune and is also released into the culture medium . It has various commercial applications but the natural function of schizophyllan during growth of S. commune is largely unknown. The S. commune strain H4-8A was grown on minimal medium (MM-N) and medium containing 10-fold more KH2PO4/K2HPO4 buffer (MM-NKP). The addition of extra buffer resulted in a 4.2-fold decrease in water-soluble schizophyllan and a 8.8-fold decrease in rigid schizophyllan in the cell wall. This decrease in schizophyllan was associated with a 3.7 fold lower tensile strength and a 2.5-fold higher elasticity of the mycelium. Moreover, spores of S. commune , as well as cells of Escherichia coli and Pseudomonas putida , showed increased survival against heat treatment and freeze-thawing, and had a longer shelf-life in the presence of schizophyllan. Also, schizophyllan can be metabolized by S. commune but the tested bacteria were unable to do so. Together, schizophyllan provides rigidity to the cell wall, protects S. commune against temperature stress, and can be used as an external carbon storage. It may also form a selective barrier around the hyphae, protecting S. commune against attack by bacteria.