Extracellular expression of Aerococcus viridans pyruvate oxidase in recombinant Escherichia coli through SecB co-expression

Pyruvate oxidase (POD) is an important enzyme used for clinical applications and biochemical analyses, and recombinant Escherichia coli strains expressing Aerococcus viridans POD have been frequently employed for obtaining high POD yield. Although significant progress has been achieved in increasing recombinant POD production, intracellular POD expression and weak stability of POD make POD purification difficult. In this study, extracellular POD expression was achieved by co-expression of chaperone SecB under three promoters (T7, lac, bla). The weakest promoter, bla, when compared with T7 and lac promoters, provided the optimum extracellular POD activity among these three promoters. After optimization of cultivation conditions, such as IPTG concentration, pH, and temperature, the extracellular POD yield increased to 795.7 U L(−1). Furthermore, by using glycine to disrupt recombinant E. coli cell wall and Cu(2+) ions as POD stabilizer, the final extracellular POD yield reached 2926.3 U L(−1). The expression intensity of chaperone had significant influence on heterologous protein secretion, and the high yield of extracellular POD implies potential widespread POD production and application.