The Screening Strain Of Dehalogenases

Halohydrin dehalogenases can catalyze the reversible formation of epoxides from vicinal halohydrins. The epoxides have a great role in the pharmaceutical field because they can react with some nucleophilicreagents, such as halogens, carbon, nitrogen, oxygen, sulphur and so on.The experiment was studied to find a strain that can catalyse the epoxides from para-nitro-2-bromo-l-phenylethanol from 73 strains cultivated using chloroactic acid as the only carbon sources. These strains were screened from the soil samples that collected from all over the country.52 strains with different ability of transforming were obtained using qualitative testing of nitric acid silver reaction. Finally, though testing the conversion and selectivity of enatiomers by using HPLC, the 17th strain was screened out.The carbon sources, nitrogen sources, inducer, iron ions, pH of the culture medium, temperature and time were studied to get the best condition to culture the 17th strain. The experiment result was that the value of pH was 6.5, the optimum temperature was 35℃, the best culture time was 35 hours. The optimum culture medium consisted of lactose 8 g/L, tryptone 6 g/L, chloroactic acid 4 g/L, Na2HPO4 3.2 g/L, KH2PO4 1.5 g/L, MgSO4 98 mg/L, CaCl2 10 mg/L, FeSO4 1 mg/L, and ZnSO4 0.1 mg/L. The maximum enzyme activity was reached 132.80 U/mg.The concentration of substrate (para-nitro-2-bromo-l-phenylethanol), buffer, reaction time temperature and so on in the catalyze reaction also be discussed in the experiment. As a result, the substrate concentration 1 g/L in aqueous environment,35℃, reacting 12 hours was optimum in the comparison experiment. The transformation rate of para-nitro-2-bromo-1-phenylethanol was 90.6%.In conclusion, the 17th strain as a better bacterial enzyme can catalyze the reversible formation of epoxides from vicinal halohydrin, however, it can not select enantiomers correctly.