2022, 30(2):183-189.
Abstract:
Two microbial strains Bacillus subtilis HDJ1 and Bacillus velezensis HDJ2 were screened from soybean paste samples by corn gluten meal medium for high protease activity. Single factor fermentation experiment showed that the optimum conditions of liquid fermentation of corn gluten meal for strain HDJ1 were: fermentation temperature of 40 ℃, fermentation pH 8, inoculum of 6%, substrate concentration of 8%, rotating speed of 200 r/min, liquid-adding volume of 40 mL, fermentation time of 72 h; The optimum conditions for liquid fermentation of corn gluten meal for strain HDJ2 were: fermentation temperature of 40 ℃, fermentation pH 6, inoculum of 9%, substrate concentration of 8%, rotating speed of 150 r/min, liquid-adding volume of 120 mL, fermentation time of 72 h; The optimum conditions for the fermentation of corn gluten meal for equal combination of HDJ1 and HDJ2 were: fermentation temperature of 30 ℃, fermentation pH 8, inoculum amount of 6%, substrate concentration of 8%, rotating speed of 250 r/min, liquid-adding volume of 40 mL, fermentation time of 96 h. The results of Orthogonal test showed that the content of soluble protein of HDJ1, HDJ2, HDJ1 and HDJ2 was the highest when the fermentation temperature was 30 ℃, the fermentation pH was 8, the inoculum amount was 3%, the substrate concentration was 8%, therotation speed was 200 r/min, and the fermentation time was 96 h. The protease activity, soluble protein content and DPPH scavenging rate of the sample significantly increased after freeze-drying of the microbial fermentation, and the fermentation effect of the two combined stains was better than that of single strain.
