Isolation and identification of a β-glucosidase-producing strain and enzymatic characteristics of the β-glucosidase
一株β-葡萄糖苷酶产生菌株的分离鉴定及酶学性质研究

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.Me-thods] 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.