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.
ABSTRACT
Objective To investigate the chemical constituents from the ethanol extract of Ulva pertusa. Methods The compounds were isolated and purified by chromatography on silica gel, ODS, Diaion HP-20, Sephadex LH-20, and preparative HPLC methods. Their structures were elucidated on the basis of spectral data. Results Eighteen compounds were isolated and identified as isophitol (1), indole-3-carboxylic acid (2), 1-O-palmitoyl-3-O-(6'-sulfo-α-D-quinovopyranosyl) glycerol (3), (2S)-1-O-palmitoyl-3-O-[α-D- galactopyranosyl-(1→2)-β-D-galactopyranosyl] glycerol (4), 3-methylsulfoxypropionic acid (5), 3-chloropropionic acid (6), tyrosol (7), 4-hydroxybenzoic acid (8), 4-hydroxyphenylacetic acid (9), 6-vinyl hexanolide (10), loliolide (11), annuionone D (12), azelaic acid (13), succinic acid (14), 8-hydroxy-(6E)-octenoic acid (15), 3-ethoxypropionic acid (16), n-butyl β-D-fructopyranoside (17), and n-butyl pyroglutamate (18). Conclusion Compounds 1-16 are isolated from this alga for the first time, and compounds 5, 6, 10, 15, and 16 are obtained from natural products for the first time. Compounds 17 and 18 are artifacts of isolation from β-D-fructopyranoside and pyroglutamic acid.