No 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 Hg 2+ and Ag 2+ 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.

Aims: Lectins are carbohydrates with structure usually binding with proteins. The isolation of lectins from local and inexpensive sources, such as rice, considered one of the chief cereal crops, is necessary due to its broad application. Methods: Lectin was extracted from a novel source, Oryza sativa grains, with solvent (hexane) of ratios (1:5 w/v) for 15 minutes. The extract solution was fractionated with ammonium sulfate at 25-65% saturation concentrations and then applied to a DEAE-cellulose column followed by a Sephadex G-100 column. SDS-PAGE has been done to vitrify from lectin purity. An enhancement and inhibition activities were calculated to detect the effect of lectin on lactic acid bacteria and pathogenic bacterial growth. The extracted lectin from three types of Oryza sativa grains showed various levels of erythrocyte agglutination from 8 to 32U/ml. Then, the specimen was loaded into a DEAE-cellulose column followed by gel using Sephadex G-100 column with a final specific activity of 246.15U/mg, 24.15 fold of purification and 70% yield of lectin. Findings: Lectin SDS-PAGE result revealed a single protein band with 43 k Da. The purified lectin exhibited a substantial prebiotic property of lactic acid bacteria growth enhancement while exhibiting apparent growth inhibition against tested pathogenic bacteria. Typically, prebiotic properties should inhibit the growth of pathogens and enhance the growth of beneficial and desirable bacteria like Lactobacillus reuteri. Conclusion: The lectin may be used in animal diet to improve digestibility and support gastrointestinal tract health. Keywords: Inhibitor agent; lectin; prebiotic; purification; Phyto hemagglutinins; rice grains.

No abstract