Optimization on liquid- state fermentation process of composite peptides from soybean and corn proteins

Soybean and corn gluten meal were mixed as fermentation materials and inoculated with Bacillus subtilis to produce composite peptides from soybean and corn protein.Firstly,effects of fermentation temperature,shaker speed,fermentation time and inoculum volume on degree of hydrolysis( DH) of proteins mixture and conversion rate of peptides were discussed. On the basis of single factor experiments,liquid- state fermentation process conditions of soybean and corn composite peptides were optimized by using four- factor three- level response surface methodology,and corresponding regression models were established. Results showed that proportion of soybean and corn gluten meal was 2 ∶ 1 and that optimum fermentation process parameters were as follows:fermentation temperature of 37 ℃,shaker speed of 184 r / min,fermentation time of 51 h,inoculum volume of 4%.Under these liquid- state fermentation conditions,DH of composite proteins was 25.73% ± 1.78% and peptide conversion rate of 33.23% ± 1.06%,which was consistent with theoretical prediction values basically. These results contributed to scientific reference for deep manufacture and application of soybean and corn gluten meal.