Identification and characterization of a multidomain hyperthermophilic cellulase from an archaeal enrichment

Despite extensive studies on microbial and enzymatic lignocellulose degradation, relatively few Archaea are known to deconstruct crystalline cellulose. Here we describe a consortium of three hyperthermophilic archaea enriched from a continental geothermal source by growth at 90 degrees C on crystalline cellulose, representing the first instance of Archaea able to deconstruct lignocellulose optimally above 90 degrees C. Following metagenomic studies on the consortium, a 90 kDa, multidomain cellulase, annotated as a member of the TIM barrel glycosyl hydrolase superfamily, was characterized. The multidomain architecture of this protein is uncommon for hyperthermophilic endoglucanases, and two of the four domains of the enzyme have no characterized homologues. The recombinant enzyme has optimal activity at 109 degrees C, a half-life of 5 h at 100 degrees C, and resists denaturation in strong detergents, high-salt concentrations, and ionic liquids. Cellulases active above 100 degrees C may assist in biofuel production from lignocellulosic feedstocks by hydrolysing cellulose under conditions typically employed in biomass pretreatment.