Enhanced shear protection and increased production of an anti-tumor polysaccharide by Agaricus blazei in xanthan-supplemented cultures

Xanthan supplementation provided shear protection and stimulated polysaccharide production by Agaricus blazei. In xanthan-free cultures, the optimal cell yield, 0.63 g biomass g^-1 glucose, and product yield, 0.19 g polysaccharide g^-1 glucose, were, respectively, when the critical impeller tip speed was 50.3 cm s^-1 and 100.5 cm s^-1. Furthermore, the critical impeller tip speed of cell yield shifted from 50.3 cm s^-1 to 100.5 cm s^-1 with the supplementation of 1 g xanthan l^-1. Maximum specific product yield, namely 0.74 g polysaccharide g^-1 biomass, was achieved with inlet air supply of 3% O₂ and impeller tip speed of 100.5 cm s^-1.