Antibacterial Efficacy and Optimized Protease-producing Capability of Brevibacillus formosus FJAT-10011

Antibacterial efficacy andprotease-producing capability of Brevibacillus formosus FJAT-10011 were studied.Screening and optimizing the culture conditions were conducted with a single-factor test and an orthogonal experiment.The optimal medium was determined to contain 1.25% starch,1.25% peptone,0.3% beef extract powder,0.5% NaCl,0.05% MgSO4,and 0.05% K2 HPO4.The optimized fermentation process included the following conditions:an initial pH of 5.5,a temperature at 25℃,the filling of the liquid medium at 30 mL/250 mL,a bacterial inoculum rate at 1%,and a fermentation duration of 24 h.Under these conditions,the protease activity of the supernatant of the liquid medium reached 8.41U·mL-1,which was 141 times greater than that in the beginning of the fermentation.The diameter of the antibacterial zone shown on a petri dish test was 15.71 mm,a 35.31%increase as compared to the non-optimized control.