According to phospholipase A1 accessory protein sequences of plaS from GenBank, 35 amino acids at N-terminal of PlaS was removed based on bioinformatics analysis.The truncated accessory proteins plaS gene was amplified by PCR and inserted into prokaryotic expression vector pET-28a (+) connection, and then the plasmid was transformed into BL21 (DE3) host bacteria for fusion expression, thereby successfully constructed dSP28 expression strain.IPTG was used to induce the expression of accessory proteins.The induction time, IPTG concentration, initial bacterial concentration (OD600nm) and temperature were optimized step by step.The optimum induction conditions were as follows: the induction time was 8 hours, the IPTG concentration was 0.2 mmol/L, the initial concentration (OD600nm) was 0.7, the temperature was 40 ℃, the rotation speed was 200 r/min.Under these conditions, OD600nm was determined in P28, SP28 and dSP28 fermentations.The results showed that P28 and dSP28 could proliferate rapidly after induction with IPTG, and the growth of P28 and dSP28 could be increased even after induction for 8 h, and the growth of SP28 was inhibited obviously.