The potential of a novel β-specific dehalogenase from Bacillus cereus WH2 as a bioremediation agent for the removal of β-haloalkanoic acids
- Author:
Wafaa Hassan Muslem
;
Mohamed Faraj Edbeib
;
Roswanira Abdul Wahab
;
Elham Khalili
;
Iffah Izzati Zakaria
;
Fahrul Huyop
- Publication Type:Original article
- Keywords:
Dehalogenase;
Bacillus cereus;
3-chloropropionic acid;
β-haloalkanoic acid;
bioremediation
- From:Malaysian Journal of Microbiology
2017;13(4):298-307
- CountryMalaysia
- Language:English
-
Abstract:
Aims: This study aims to describe the biochemical and kinetic properties of a dehalogenase produced by a bacterium,
Bacillus cereus WH2 (KU721999), that is uniquely adept at degrading a β-haloalkanoic acid, i.e., 3-chloropropionic acid
(3-CP), and using it as the bacterium’s sole carbon source. The bacterium was isolated from abandoned agricultural
land in Universiti Teknologi Malaysia that was previously exposed to herbicides and pesticides.
Methodology and results: The B. cereus impressively removed 97% of 3-CP after 36 h of culturing. The intracellular
WH2 dehalogenase of the bacterium was purified 2.5-fold and has an estimated molecular mass of 37 kDa. The highest
activity of the dehalogenase was achieved under conditions of 30 °C and pH 7. The metal ions Hg2+ and Ag2+
substantially repressed the enzyme’s activity, but the enzyme’s activity was uninhibited by dithiothreitol (DTT) and
EDTA. The WH2 dehalogenase showed a higher affinity for 3-CP (Km = 0.32 mM, kcat = 5.74 s-1
) than for 3-chlorobutyric
acid (3-CB) (Km = 0.52 mM; kcat = 5.60 s-1
). The enzyme was ~1.6-fold more catalytically efficient (kcat/Km) in
dehalogenating the three-carbon substrate 3-CP (17.8 mM-1 s
-1
) than the four-carbon 3-CB (11.2 mM-1 s
-1
).
Conclusion, significance and impact of study: The novel B. cereus bacterium isolated in this study may prove
applicable as a bioremediation agent to cleaning environments that are polluted with β-halogenated compounds.
Furthermore, such an approach to treat polluted environments is more sustainable and potentially safer than chemical
treatments.
