Optimization of medium composition and fermentation conditions for the production of thermophilic cellulase by Aspergillus sp.

An Aspergillus sp.strain F4 capable of producing thermophilic cellulases was previously selected in the laboratory.The studies presented here described the optimization of medium components and process parameters for cellulase production by the strain using liquid fermentation.The effect of carbon sources,nitrogen sources,salts and initial culture pH on enzyme production was evaluated,and the best fermentation medium was found to be: 40 g·L-1 rice straw powder,3.5 g·L-1(NH4)2SO4,2 g·L-1 NaCl,2 g·L-1 KH2PO4,0.5 g·L-1 MgSO4·7H2O,0.2% glycerine,pH5.5,which resulted in a 16.7-fold increase of CMCase yield.The inoculum size of 4% and culture volume of 80 mL/250 mL flask were optimum for cellulase production by strain F4.When incubated at 37 ℃ with the shaking speed of 150 r·min-1,highest CMCase activity of 12.26 U·mL-1(with another 2-fold increase) was seen after a period of 8 d.