Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 4/18/2006
Publication Date: 2/21/2007
Citation: Lynd, L.R., Weimer, P.J., Wolfaardt, G.M., Zhang, Y.P. 2007. Cellulose hydrolysis by Clostridium thermocellum: A microbial perspective. In: Kataeva, I.A., editor. Cellulosome: Molecular Anatomy and Physiology of Proteinaceous Machines. Hauppage, NY:Nova Science Publishers. p. 95-117. Interpretive Summary: An ethanol-producing bacterium known as Clostridium thermocellum has provided scientists a useful experimental system for understanding how cellulosic biomass is degraded. This bacterium produces a “cellulosome”, a special structure at the cell surface that contains the enzymes for breaking cellulose into smaller units that the cell can metabolize. Recent evidence indicates that the process of cellulose breakdown, while performed by the cellulosome, is actually controlled by the metabolic activities of the cell. Optimizing the regulation of cellulosome activity may provide a means of improving processes to produce chemicals and fuels from plant residues and other cellulosic biomass materials.
Technical Abstract: The thermophile Clostridium thermocellum has served as the model system for the study of the cellulosome organelle present in most anaerobic cellulolytic bacteria. Recent evidence suggests that synergy between the cellulosome and the bacterium is a major determinant of the catalytic efficiency of the organelle during the process of cellulose degradation. Thus an understanding of the process of anaerobic cellulose degradation cannot be achieved solely through a molecular-level understanding of the cellulosome, but requires a more complete understanding of the physiology and metabolism of the host organism. This chapter reviews organismal aspects of C. thermocellum, including the ecophysiology of the organism; the mechanism of cellulose hydrolysis; bioenergetics; control of cellulase synthesis; mechanisms of adhesion; and the concept of microbial cellulose hydrolysis as a reacting biofilm. Recent advances are used to provide a perspective on expanding frontiers of microbial cellulose utilization.