Purifying, cloning and characterizing a novel dehalogenase from Bacillus sp. GZT to enhance the biodegradation of 2,4,6-Tribromophenol (cas 118-79-6) in water☆

Add time:09/03/2019    Source:sciencedirect.com

2,4,6-Tribromophenol (cas 118-79-6) (TBP), an intermediate of brominated flame retardants, can easily release to environment and recalcitrant to degradation. Previously, Bacillus sp. GZT, a pure aerobic strain capable of simultaneously debrominating and mineralizing TBP, was successfully isolated by us. To further obtain a practical application and dig up its TBP degradation mechanism, a total of 46.7-fold purification of a novel dehalogenase with a final specific activity of 18.9 U mg−1 and a molecular mass of 63.4 kDa was achieved. Under optimal conditions (35 °C and 200 rpm), up to 80% degradation efficiencies were achieved within 120 min. Adding H2O2, NADPH, Mn2+ and Mg2+ promoted enzyme reaction effectively; while EDTA, methyl viologen, Ni2+, Cu2+, Ca2+ and Fe2+ strongly inhibited reaction activities. The debromination of TBP was catalyzed by the enzyme at a Km of 78 μM and a Vmax of 0.65 min−1 mg protein−1, which indicated that this dehalogenase could specifically eliminate TBP with a high efficiency and stability. Based on MALDI-TOF/TOF analysis, the dehalogenase shared 98% identity with peptide ABC transporter substrate-binding protein. One open reading frame (ORF) encoding this peptide was found in Strain GZT genome, subjected to clone and expressed in Escherichia coli (E. coli) to characterize the encoding gene. Result showed that this recombinant strain could also remove as similar amount of TBP as Bacillus sp. GZT under the identical condition. Based on these results, we suggest that this newly-isolated TBP dehalogenase highlights a new approach for remediating TBP pollution.

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