Improved Production and Rheological Properties of Exopolysaccharides by Co-Overexpression of β-1,3-Glucan Synthase and UDP-Glucose Pyrophosphorylase Genes in Ganoderma lingzhi

The β-1,3-glucan synthase gene 2 (gls2) from the biosynthetic pathway of polysaccharides was cloned and overexpressed in G. lingzhi. The content of intracellular polysaccharides in the gls2 overexpression strain was 22.96 mg/100 mg of dry weight, 20% higher than that in the wild-type (WT) strain. The effect of co-overexpression of gls2, UDP-glucose pyrophosphorylase gene (ugp), and gls on polysaccharide biosynthesis was also investigated in G. lingzhi. The production of extracellular polysaccharides (EPS) in the G2-U-G transformants was 62% higher than that in the WT strain. Moreover, EPS from G2-U-G transformants had a higher molecular weight and glucose levels (6.3 × 103 kDa and 89.19%) than those from the WT strain (4.8 × 103 kDa and 78.15%), respectively. Furthermore, they showed higher viscosity, greater thixotropy, and a stronger gel network than EPS from the WT strain. Overall, this study contributes to the efficient production, development, and application of Ganoderma exopolysaccharides.