Cost Effective Method of Protease Production in Solid State Fermentation Using Combined Substrate Corn Cob and Lentil Husk

Abstract

An alkalophilic Bacillus cereus strain was found to produce a thermal and pH tolerant extracellular alkaline protease which showed very good compatibility and stability with commercial laundry detergents. Considering important industrial application of B. cereus protease, its production needs to be enhanced. Different agro-industrial waste products, viz., wheat bran, lentil husk, green gram husk and corn cob were used as substrates for the production of B. cereus protease by solid state fermentation (SSF). The production of alkaline protease in SSF was compared with that in submerged fermentation (SmF) by using the same substrates. This comparative study revealed that production of B. cereus protease is significantly higher in SSF than in SmF. Among all the substrates used, corn cob followed by lentil husk showed best production in SSF. Combined effect of corn cob and lentil husk was examined when mixed in 1:1 ratio. The production of protease was enhanced almost double in comparison to individual substrate. Other important parameters like inoculum size, substrate concentration, fermentation time, incubation temperature and moisture content were optimized to get maximum protease production in SSF. Maximum protease activity of 580.80 u/mL/min (4640 U/g solid substrate) was obtained in SSF when initial moisture content was maintained at 60%, 3 g of corn cob and lentil husk were used in 1:1 ratio, 2.0–2.5 mL (2 mg/mL) of inoculum was added and culture was incubated at 30 °C for 7 days.
Keywords: Bacillus cereus, alkaline protease, solid state fermentation, corn cob, lentil husk