Optimization of alkaline protease production from Bacillus licheniformis D5 in submerged fermentation

Abstract

Enzymes are important raw material for the detergent industry. In order to develop enzymes for detergents, Bacillus licheniformis D5, a strain with high alkaline protease production, was screened in this study. The alkaline protease production was optimized using response surface methodology (RSM). The optimized fermentation medium (w/v) consisted of soybean cake flour (4.0%), peanut cake flour (2.69%), beef paste (0.95%), maltodextrin (4.0%), glucose (2.23%), KCl (0.1%), KH₂PO₄ (0.2%), K₂HPO₄·12H₂O (0.40%), CaCl₂ (0.04%), MgSO₄·7H₂O (0.04%), Tween-80 (0.05%) and serine (0.05%). The fermentation level increased by 2.12-fold compared with the control. The culture temperature was 33°C, and the initial pH was 10. The fed-batch fermentation was performed in a 30 L fermenter. The fermentation level was increased by 47.4% (from 43,587 U/mL to 60,830 U/mL), and the fermentation time was shortened from 78 h to 54 h. The results demonstrated significantly improved fermentation level, reduced fermentation cost, simplified large-scale production of alkaline protease, and thereby promote application of alkaline protease in detergent industry.