Characterization, Optimization, and Scaling-up of Submerged Inonotus hispidus Mycelial Fermentation for Enhanced Biomass and Polysaccharide Production.

This study was to establish an efficient strategy based on inoculum-morphology control for the submerged mycelial fermentation of an edible and medicinal fungus, Inonotus hispidus. Two major morphological forms of the mycelial inoculum were compared, dispersed mycelial fragments versus aggregated mycelial clumps. The dispersed one was more favorable for the fermentation, starting with a shorter lag period and attaining a higher biomass yield and more uniform mycelium pellets in shake flasks. The mycelial pellets taken from the shake flask culture on day 6 were fragmented at 26,000 rpm in a homogenizer, and a shear time of 3 min provided the optimal inoculum. The inoculum and culture conditions were further verified in 5-L stirred tank fermenters and then the fermentation was scaled-up in a 100-L stirred tank. With the optimized inoculum and process conditions plus a fed-batch operation, much higher productivities, including 22.23 g/L biomass, 3.31 g/L EPS, and 5.21 g/L IPS, were achieved in the 100-L fermenter than in the flask culture. A composition analysis showed that the I. hispidus mycelium produced by the fermentation was rich in protein, dietary fiber, and polysaccharides which may be beneficial to health. Overall, the results have shown that the inoculum characteristics including age, morphology, and state of aggregation have significant impact on the productivity of mycelial biomass and polysaccharides in a submerged mycelial fermentation of the I. hispidus fungus.