Abstract:Serine carboxypeptidase could cleave the amino acid at the C-terminus of the peptide chain and has a wide range of applications in debittering soybean protein. In this study, three serine carboxypeptidase genes (CPG,CPF,CPA) from Aspergillus niger were recombinantly expressed in low-background Aspergillus niger HL-1; promoter PnaⅡ, terminator Ttef and auxotrophic selection marker pyrG were used to construct serine carboxypeptidase expression vector containing its own signal peptide and glucoamylase signal peptide; PEG-mediated transformation method was used to transform into host HL-1 to construct a serine carboxypeptidase recombinant expression strain; the high expressional recombinant strain HL-CPG was obtained by fermentation screening, and its serine carboxypeptidase activity reached 163.71 U/mL; the 6ⅹHis tag was used for nickel column affinity chromatography to obtain a single serine carboxypeptidase CPG and its enzymatic properties. The optimal reaction temperature of the enzyme was 40 ℃, the optimal pH was 3.5, and Cu2+ had a significant inhibitory effect. In addition, when serine carboxypeptidase CPG and pepsin were compounded to hydrolyze soybean protein, the content of hydrophobic amino acids Leu, Tyr and Phe in the hydrolysate increased by 606.47 μg/mL, 434.06 μg/mL and 205.11 μg/mL, respectively. In summary, this study successfully achieved high-efficiency expression of serine carboxypeptidase, and provided support for solving the debittering treatment process of soybean protein hydrolysate.
