To verify whether the CcpA gene was successfully deleted, we designed the primer for PCR. The primer was designed across the upstream and downstream sequences of the CcpA gene, with a size of about 1827bp. Results showed that two (1827bp and 1985bp) PCR products (WT2 and KO2) were produced, then the amplified DNA products of WT2 and KO2 were electrophoresed on a 1% (wt/vol) agarose gel, and sequenced by Shanghai Sangon Biological Engineering Technology and Services Co., Ltd. for further verification. The results of DNA sequencing confirmed that the CcpA deletion strain was successfully constructed.