Abstract:  Recombinant plasmid pETXB2 which contained Clostridium perfringens β2\|toxin gene was identified with restriction endonucleases digestion， and the genes expression products in Escherichia coli strain BL21（DE3） under different culture conditions were detected by SDS\|PAGE. The results were as follows: Endonucleases digestion and DNA sequencing confirmed that the recombinant expression plasmid pETXB2 contained the β2\|toxin gene in the expression cassette of pET\|28c（+） with a positive reading frame. The optimization condition of inducible expression for β2\|toxin by IPTG was 08 mmol·L-1 of IPTG concentration and inducing for 4 h at 37℃, pH 70. When induced by lactose， the optimization condition was 05 g·L-1 of lactose concentration and inducing for 5 h at 37℃, pH 70.

Key words: Clostridium perfringene type C, β2\, toxin, IPTG, lactose