title: Microbial β-glucosidases from cow rumen metagenome enhance the saccharification of lignocellulose in combination with commercial cellulase cocktail.
abstract: BACKGROUND
  A complete saccharification of plant polymers is the critical step in the efficient production of bio-alcohols. Beta-glucosidases acting in the degradation of intermediate gluco-oligosaccharides produced by cellulases limit the yield of the final product.
  
  
  RESULTS
  In the present work, we have identified and then successfully cloned, expressed, purified and characterised 4 highly active beta-glucosidases from fibre-adherent microbial community from the cow rumen. The enzymes were most active at temperatures 45-55°C and pH 4.0-7.0 and exhibited high affinity and activity towards synthetic substrates such as p-nitrophenyl-beta-D-glucopyranoside (pNPbetaG) and pNP-beta-cellobiose, as well as to natural cello-oligosaccharides ranging from cellobiose to cellopentaose. The apparent capability of the most active beta-glucosidase, herein named LAB25g2, was tested for its ability to improve, at low dosage (31.25 units g-1 dry biomass, using pNPbetaG as substrate), the hydrolysis of pre-treated corn stover (dry matter content of 20%; 350 g glucan kg-1 dry biomass) in combination with a beta-glucosidase-deficient commercial Trichoderma reseei cellulase cocktail (5 units g-1 dry biomass in the basis of pNPbetaG). LAB25g2 increased the final hydrolysis yield by a factor of 20% (44.5 ± 1.7% vs. 34.5 ± 1.5% in control conditions) after 96-120 h as compared to control reactions in its absence or in the presence of other commercial beta-glucosidase preparations. The high stability (half-life higher than 5 days at 50°C and pH 5.2) and 2-38000 fold higher (as compared with reported beta-glucosidases) activity towards cello-oligosaccharides may account for its performance in supplementation assays.
  
  
  CONCLUSIONS
  The results suggest that beta-glucosidases from yet uncultured bacteria from animal digestomes may be of a potential interest for biotechnological processes related to the effective bio-ethanol production in combination with low dosage of commercial cellulases.
authors.affiliation: CSIC, Institute of Catalysis, 28049, Madrid, Spain. mferrer@icp.csic.es.
authors.forename: Mercedes V
authors.initials: MV
authors.lastname: Del Pozo
authors.forename: Lucía
authors.initials: L
authors.lastname: Fernández-Arrojo
authors.forename: Jorge
authors.initials: J
authors.lastname: Gil-Martínez
authors.forename: Alejandro
authors.initials: A
authors.lastname: Montesinos
authors.forename: Tatyana N
authors.initials: TN
authors.lastname: Chernikova
authors.forename: Taras Y
authors.initials: TY
authors.lastname: Nechitaylo
authors.forename: Agnes
authors.initials: A
authors.lastname: Waliszek
authors.forename: Marta
authors.initials: M
authors.lastname: Tortajada
authors.forename: Antonia
authors.initials: A
authors.lastname: Rojas
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Huws
authors.forename: Olga V
authors.initials: OV
authors.lastname: Golyshina
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Newbold
authors.forename: Julio
authors.initials: J
authors.lastname: Polaina
authors.forename: Manuel
authors.initials: M
authors.lastname: Ferrer
authors.forename: Peter N
authors.initials: PN
authors.lastname: Golyshin