Abstract:[Objective] To isolate a novel β-glucosidase-producing strain from soil, to clarify the taxonomic status, and to study the enzymatic characteristics of the β-glucosidase. [Methods] A β-glucosidase-producing strain was isolated from soil sample using esculin and 4-nitrophenyl-β-D-glucopyranoside (PNPG) coloration methods; the taxonomic status of strain ZF-6C was clarified by morphological, physiological, chemotaxonomic characteristics and 16S rDNA analysis; the β-glucosidase was isolated and purified by ultra-filtration, hydrophobic interaction chromatography, anion chromatography, molecular sieve chromatography; with PNPG as the substrate, the optimal reaction pH and temperature of β-glucosidase were determined, the Michaelis constant Km of β-glucosidase against different substrates were determined by Lineweaver-Burk plot. [Results] A strain, which produced β-glucosidase at high level, was isolated from soil and identified as Bacillus korlensis, the molecular weight of β-glucosidase isolated from Bacillus ZF-6C was 90 kD, the optimum reaction conditions for this enzyme were pH 7.0 and 40 °C. The enzyme was active against a wide range of β (1,4) linked disaccharides, the optimal substrate was o-nitrophenyl-β-D-glucopyranoside, the Km value was 0.73 mmol/L. Metal ions Ca2+ and Pb2+ enhanced enzyme activity, Cu2+ and Fe2+ inhibit the enzyme activity. [Conclusion] This is the first report of isolation and identification of β-glucosidase from Bacillus korlensis. The β-glucosidase from Bacillus korlensis is widely different to known enzymes at molecular weight, optimum reaction conditions and substrate specificity aspects. This β-glucosidase may have novel structure and high catalytic efficiency.
