title: Expression and characterization of a novel highly glucose-tolerant β-glucosidase from a soil metagenome.
abstract: A β-glucosidase gene unbgl1A was isolated by the function-based screening of a metagenomic library and the enzyme protein was expressed in Escherichia coli, purified, and biochemically characterized. The enzyme Unbgl1A had a Km value of 2.09 ± 0.31 mM, and a Vmax value of 183.90 ± 9.61 μmol min(-1) mg(-1) under the optimal reaction conditions, which were pH 6.0 at 50°C. Unbgl1A can be activated by a variety of monosaccharides, disaccharides, and NaCl, and exhibits a high level of stability at high concentration of NaCl. Two prominent features for this enzyme are: (i) high glucose tolerance. It can be tolerant to glucose as high as 2000 mM, with Ki = 1500 mM; (ii) high NaCl tolerance. Its activity is not affected by 600 mM NaCl. The enzyme showed transglucosylation activities resulting in the formation of cellotriose from cellobiose. These properties of Unbgl1A should have important practical implication in its potential applications for better industrial production of glucose or bioethanol started from lignocellulosic biomass.
authors.affiliation: State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Science and Technology, Guangxi University, Nanning 530005, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Lu
authors.forename: Liqin
authors.initials: L
authors.lastname: Du
authors.forename: Yutuo
authors.initials: Y
authors.lastname: Wei
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Hu
authors.forename: Ribo
authors.initials: R
authors.lastname: Huang
mesh_terms: D000222:Adaptation, Physiological; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D005947:Glucose / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D054892:Metagenome; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012988:Soil Microbiology; D013696:Temperature; D001617:beta-Glucosidase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D001617:beta-Glucosidase; D005947:Glucose
keywords: glucose tolerance; metagenome; β-glucosidase