Increased production and anti-senescence activity of exopolysaccharides in Ganoderma lingzhi by co-overexpression of β-1,3-glucan synthase and UDP-glucose pyrophosphorylase

A β-1,3-glucan synthase gene (gls) was cloned and overexpressed in Ganoderma lingzhi. The content of intracellular polysaccharides (IPS) in G. lingzhi overexpressing gls was 22.36 mg/100 mg dry weight (DW), 19 % higher than those in the wild-type (WT) strain. Overexpression of gls did not affect the expression of the phosphoglucomutase gene and the UDP-glucose pyrophosphorylase gene (ugp) in the polysaccharide biosynthesis. The gls and ugp were then simultaneously overexpressed in G. lingzhi for the first time. The combined overexpression of these two genes increased the IPS content and exopolysaccharides (EPS) production to a greater extent than the overexpression of gls independently. The maximum IPS content of the overexpressed strain was 24.61 mg/100 mg, and the maximum EPS production was 1.55 g/L, 1.31- and 1.50-fold higher than that in the WT strain, respectively. Moreover, the major EPS fractions from the overexpression strain contained more glucose (86.7 % and 72.5 %) than those from the WT strain (78.2 % and 62.9 %). Furthermore, the major fraction G+U-0.1 from the overexpression strain exhibited stronger antioxidant and anti-senescence activities than the WT-0.1 fraction from the WT strain. These findings will aid in the hyperproduction and application of Ganoderma polysaccharides and facilitate our understanding of mushroom polysaccharide biosynthesis.