Submerged Fermentation of Ganoderma tsugae for the Optimized Production of Exopolysaccharides

Ganoderma tsugae, commonly known as the hemlock reishi, has historically played a significant role in Eastern traditional medicine. Notably, Ganoderma species are known to have medicinal properties for potential commercial use, including cholesterol reduction, lowering blood pressure, antivirals, and antitumor therapies. To fully capitalize on these medicinal benefits for commercial use, the Ganoderma mycelium and its potential therapeutic metabolites, including biologically active polysaccharides, must be produced at scale. One promising approach is to employ stirred-tank bioreactors for the submerged fermentation of mycelium. The goal of this project is to maximize exopolysaccharide (EPS) production from the submerged fermentation of G. tsugae mycelium by locating which experimental variables are optimal. Experimental variables included media formulations and enrichments, temperature, pH, and agitation speed. Mycelium cultivation involved growing G. tsugae on Potato Dextrose Agar (PDA) plates, which were then used to inoculate liquid cultures in baffled shake flasks. Samples were taken every two to four days and assayed for biomass, reducing sugars, and exopolysaccharides (EPSs). The highest biomass and exopolysaccharide production was observed in a lactose-based media with a constant temperature of 28°C, pH of 5.5, and an agitation of 120 rpm. These optimized parameters resulted in a peak biomass yield of 11.4g/L and a peak exopolysaccharide yield of 1.68g/L.