[Gene cloning and overexpression of dichloromethane dehalogenase from Bacillus circulans WZ-12]

The dcmR gene encoding dichloromethane dehalogenase was amplified by PCR from Bacillus circulans WZ-12 and cloned to expression vector pET28b(+), yielding recombinant plasmid pET28b(+)-dcmR. Then plasmid pET28b(+)-dcmR was introduced into Escherichia. coli BL21(DE3). Expression was induced by IPTG,and the enzyme activity reached 25.78 U/mL, the specific enzyme activity reached 88.86 U/mg protein.The periplasmic and cytoplasmic enzyme activity reached 2.92 U/mL and 22.86 U/mL respectively.All results analysis demonstrated that the E. coli. strain carrying the dcmR gene could produce dichloromethane dehalogenase efficiently. The growth characteristics of dcmR-1 was compared with the original strain, and the result showed that there was no difference, A(600nm) of dcmR-1 in LB medium could reach about 2.4 in logarithmic period,which was the same as that of the original strain. The recombinant strain dcmR-1 showed the higher degrading ability than Bacillus circulans WZ-12 and with more than 90% removal efficiency of 120 mmol/L CH2Cl2 in 25 h. All these results indicated that recombinant strain dcmR-1 was a promising strain in bioremediation of CH2Cl2 contaminated environment.