ARS | Publication request: Characterization of Carboxymethylcellulase Activity from Geobacillus Stearothermophilus

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: August 25, 2005
Publication Date: August 25, 2005
Citation: Bischoff, K.M., Li, X., Rooney, A.P., Liu, S., Hughes, S.R. 2005. Characterization of carboxymethylcellulase activity from Geobacillus stearothermophilus [abstract]. Society for Industrial Microbiology. Paper #P38.

Technical Abstract: One of the technological impediments to widespread utilization of lignocellulosic biomass as a fermentation feedstock is the efficient and economical depolymerization of the polysaccharides found in cellulose and hemicellulose. A rational strategy toward overcoming this hurdle is the isolation of hydrolytic enzymes from thermophilic microorganisms to convert biomass to its constituent monomeric sugars. Twenty-nine strains of thermophilic bacteria that were deposited as Geobacillus stearothermophilus in the NCAUR culture collection were screened for the production of cellulolytic and xylanolytic activity by gel diffusion assay on selective media. One strain tested positive for cellulolytic activity, and cell-free culture supernatants were found to contain a carboxymethylcellulase (CMCase). Cultures grown in rich media supplemented with either glucose or xylose at 0.1% (w/v) produced approximately 4-fold more enzymatic activity than those grown in rich media alone or those supplemented with carboxymethylcellulose. The optimal temperature for activity was 55°C and the enzyme was remarkably stable at this temperature, retaining 90% of its activity following incubation for 18 h. Maximal activity was observed in the pH range of 4.5 ¿ 6.0, but samples retained approximately 60% and 70% of maximal activity at pH 4.0 and pH 8.0, respectively. Zymogram analysis following SDS-PAGE of extracellular protein indicated that the CMCase has a mass of approximately 48 kDa. The broad pH range and thermophilic properties of this enzyme may prove suitable for application in the conversion of biomass to glucose for production of fuel ethanol or other valuable fermentation products.