Scale-up study on the fed-batch fermentation of Ganoderma lucidum for the hyperproduction of ganoderic acid and Ganoderma polysaccharides

Besides the identified key factors of pH-shift from 3.0 to 4.5 on day 4 and dissolved oxygen tension (DOT) shift from 25 to 10% on day 6, lower shear stress was also demonstrated to be a key factor in scaling-up the fed-batch fermentation of the medicinal mushroom Ganoderma lucidum from a shake flask to a stirred-tank bioreactor. The maximal biomass (22.62 g/L), intercellular polysaccharide production (4.74 g/L), and ganoderic acid production (798.0 mg/L) were attained at a low impeller tip speed of 1.234 m/s. Based on the identified key factors of pH-shift, DOT-shift and lower shear stress, the fed-batch fermentation of G. lucidum was successfully step-wise scaled-up from 7.5- to 200-L stirred-tank bioreactor. Through the qualitative and quantitative side-by-side comparison of G. lucidum growth and metabolites accumulation, it was concluded that the comparability of the fed-batch fermentation process were well controlled and the products were maintained during the process scale-up.