Effect of microwave radiation combined with cellulase treatment of soybean residue on the culture of Aspergillus oryzae

Abstract

Soybean residue (SR) is a by-product of bean product processing with potential usefulness as a fermentation medium. However, the fermentation efficiency of SR is limited due to its low reducing sugar content. In this study, a method of microwave radiation combined with cellulase hydrolysis (MCH) was developed to increase the reducing sugar content of SR, and the effect of treated SR on fermentation by Aspergillus oryzae was evaluated. First, the process parameters, including the reaction time, pH and temperature, were optimized. Second, the effect of treated SR on fermentation by A. oryzae was evaluated, including changes in cell proliferation and protease viability. The results showed that the MCH method capitalized on the advantages of microwave radiation and cellulase and promoted the enzymatic hydrolysis of fibrous polysaccharides in the crystallization zone of SR. The reducing sugar content of SR significantly increased from 0.42 to 0.98 mg/mL after MCH treatment. In addition, treated SR effectively promoted the proliferation of A. oryzae, and the protease activity reached 111 U/mL after 3 days of fermentation. The results of this study suggested that the MCH method can effectively increase the reducing sugar content of SR to expand its use as a fermentation medium.