Screening and Engineering of Geobacillus spp. for Consolidated Bioprocessing of Lignocellulosic Biomass

Abstract

Current lignocellulosic fermentation depend on complex and expensive enzymatic hydrolysis of cellulose and hemicellulose. In order to make bioprocessing of lignocellulose economically competitive this study has selected and engineered a host for degradation of cellulose, into simple monomeric sugars. Geobacillus thermoglucosidans DSM 2542 was engineered to individually express four cellulase proteins. The proteins chosen were CelA, CelB Cel6B and Cel9A from Caldicellulosciruptor bescii, Thermotoga neopolitania and Thermobifida fusca respectively. CelA, CelB and Cel9A were shown to be active against carboxymethylcellulose (CMC). CelA is of particular interest as the protein has been shown to be multifunctional, thermostable at 55 ºC, has a novel mode of action and able to degrade biomass through surface ablation and cavity formation. The cellulase genes were placed under the control of an inducible promoter (ParaE) to facilitate regulation of gene expression with arabinose. This study represents considerable progress in the engineering of G. thermoglucosidans for use in a consolidated bioprocessing system.