Optimization of enzymatic hydrolysis of the substrate of Tilapia by-products produced lipo-peptide based on high hydrolysis

On the basis of producing lipopeptide with Tilapia by-products, adopting endogenous enzyme to enzymolysis it to improve the utilization ratio of protein and increase the amount of active peptides. Using Tilapia by-products as the main fermentation substrates, and inoculating the antibacterial lipopeptide high-yield strains Bacillus natto NT-6 for solid-state fermentation for 48 h.The optimal enzymolysis conditions were achieved by the single factor test and response surface method with the degree of hydrolysis of protein as the main indicator, and other indicators in the end-product were also measured.The results showed that the optimal enzymolysis conditions were temperature 48 ℃, enzymatic time 8 h, pH7.5, and ratio of water to material 1∶ 1, with the highest degree of hydrolysis up to 37.56%, increased by 44.46% compared with the first stage, and enzymolysis had no significant effect on the content of lipopeptide.In the enzymolysis product, the content of crude protein was up to 32.13 g/100 g ( dry weight) , oligopeptide was 12.09%, and the amount of probiotic of Bacillus natto NT-6 was about 9.0 × 10⁸ cfu/g ( dry weight) .In addition, the digestibility of protein in vitro, protein solubility and the content of essential amino acid increased obviously after fermentation, especially the content of free amino acid, reaching 4.21%, and all these make the quality of product improved significantly. The parameters obtained in this study can provide scientific guidance for the production of antibacterial and nutritional compound active peptides using Tilapia by-products.