Study On Optimization Of Fermentation And Application Of A Multi-enzyme Bacillus Subtilis

Bacillus subtilis, the most widely discussed microorganism, played an important part in feed industry, aquaculture industry, biological control and molecular biology. The present study was an optimization focus on the fermentation of the B.subtilis, which can enhance the yield of all the enzymes. Then solid-sate fermentation was built up to process the soybean meal, which was succeeded in the end. The research has a practical significance on reduce the cost of the feed industry, also it can do great job in pushing the development of the aquaculture industry.The present study began with screening the multi-enzyme strain. From the strains saved in the lab, a strain was screened out which was identified as B.subtilis. The strain can produce five high-active enzymes including protease, xylanase, amylase, mannanase and cellulase. Based on the characteristic of the culture and fermentation, an experienced medium (20g/L of Soybean Meal,20g/L of Wheat Bran,1g/L of (NH4)2SO4,6g/L of CaCl2,0.3g/L of K2HPO4,0.2g/L of MnSO4H2O and0.2g/L of MgSO4-7H2O) was used for the strain fermentation, and the significant variables for the medium formulation were investigated using the Plackett-Burman design with the protease yield as the dependent variable. After the confirmation of the variables with response surface methodology, the optimized medium formulation was established to be17.3g/L of Soybean Meal,4.4g/L of CaCl2,0.23g/L of K2HPO4.A series of experiments were designed and conducted to optimize the fermentation conditions by single factor optimization. Based on all the experimental results, the optimized fermentation conditions for the strain can be established to be2%of inoculums size, and cultivation of the inoculums and the strain at37℃for12h and48h, respectively. After the optimization, the protease yield was increased by60%(1895.6U/mL) and the yields of the other four enzymes were improved to a varying degree.When the solid fermentation with soybean meal was completed, the content of oligopeptide and monosaccharide in the treated soybean meal was increased from0.41% to5.61%and1.53%to6.07%, respectively, demonstrating the significant effect of the multi-enzyme complex on the content of oligopeptide and monosaccharide in the treated soybean meal, which has met the content requirements of feed industry.