Two promising alkaline β-glucosidases isolated by functional metagenomics from agricultural soil, including one showing high tolerance towards harsh detergents, oxidants and glucose

J Ind Microbiol Biotechnol. 2014 Mar;41(3):479-88. doi: 10.1007/s10295-014-1400-0. Epub 2014 Jan 12.

Abstract

New β-glucosidase activities were identified by screening metagenomic libraries constructed with DNA isolated from the topsoil of a winter wheat field. Two of the corresponding proteins, displaying an unusual preference for alkaline conditions, were selected for purification by Ni-NTA chromatography. AS-Esc6, a 762-amino-acid enzyme belonging to glycoside hydrolase family 3, proved to be a mesophilic aryl-β-glucosidase with maximal activity around pH 8 and 40 °C. A similar pH optimum was found for AS-Esc10, a 475-amino-acid GH1-family enzyme, but this enzyme remained significantly active across a wider pH range and was also markedly more stable than AS-Esc6 at pH greater than 10. AS-Esc10 was found to degrade cellobiose and diverse aryl glycosides, with an optimal temperature of 60 °C and good stability up to 50 °C. Unlike AS-Esc6, which showed a classically low inhibitory constant for glucose (14 mM), AS-Esc10 showed enhanced activity in the presence of molar concentrations of glucose. AS-Esc10 was highly tolerant to hydrogen peroxide and also to sodium dodecyl sulfate, this being indicative of kinetic stability. This unique combination of properties makes AS-Esc10 a particularly promising candidate whose potential in biotechnological applications is worth exploring further.

MeSH terms

  • Detergents / metabolism
  • Glucose / metabolism
  • Hydrogen-Ion Concentration
  • Kinetics
  • Metagenomics*
  • Molecular Sequence Data
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Soil / chemistry*
  • Substrate Specificity
  • Temperature
  • beta-Glucosidase / chemistry
  • beta-Glucosidase / genetics*
  • beta-Glucosidase / isolation & purification*
  • beta-Glucosidase / metabolism

Substances

  • Detergents
  • Recombinant Proteins
  • Soil
  • beta-Glucosidase
  • Glucose

Associated data

  • GENBANK/KF660587
  • GENBANK/KF660588