Biofuels & Bioenergy

Cellulose is the major component of the plant cell wall and as such comprises the most abundant renewable source of carbon and energy on our planet. This fact has spawned, in the last decade, a tremendous amount of interest in the use of cellulosic biomass to at least partially alleviate the burden and dependence of our society on fossil fuels. In the plant cell wall, however, cellulose and other polysaccharides assume a structural rather than a storage role, and their monosaccharide residues – whose facile production is the key to the subsequent processing of liquid biofuels – are essentially inaccessible to microbes and their polysaccharide-degrading enzymes. Unlike aerobic fungi and bacteria, various anaerobic bacteria secrete potent multi-enzyme cellulosome complexes, which contain numerous cellulases, hemicellulases and associated enzymes, attached to the bacterial cell surface, thus enabling efficient degradation of cellulosic substrates. We have exploited the enhanced synergistic properties of cellulosomes by reconfiguring their Lego-like multi-modular components into discrete artificial complexes of predetermined design. We have thus dismantled the cellulosome into its component parts and reassembled them into “designer cellulosomes” of precise content and organization. Designer cellulosomes provide a promising platform for understanding the rationale behind its catalytic efficiency, and knowledge gained from their study may provide the basis for creating improved multi-enzyme assemblies for efficient cost-effective conversion of plant-derived biomass into liquid biofuels.