The Role of Cellulose-Hydrolyzing Bacteria in the Production of Biogas from Plant Biomass

Abstract

Biological decomposition of biomass, i.e., the abundant and renewably produced whole plant biomass, is the basis for the production of bioenergy and platform chemicals in a biorefinery. Biogas formation is presently the most energy-efficient, versatile, and mature technology of producing energy and (potentially) a number of useful by-products. It can use a wide range of dedicated energy crops and by-products from the biorefinery. Biogas is easily stored and distributed by the existing infrastructure and can be used directly by the end consumers. Although biogas fermentation from plant biomass uses mature technology, the efficiency and yield of biogas plants can however still be increased. Little is, for instance, known about the underlying biology, and the biological basis of the process is not completely understood. This review deals with the first step of biogas fermentation, the hydrolysis of the polysaccharides in plant biomass. It is regarded as one of the rate-limiting steps in the process. It also determines the overall efficiency of the process. Cellulose is recalcitrant to enzymatic hydrolysis and needs special enzyme systems which are produced by a limited number of specialized microorganisms. Various bacterial enzyme systems for cellulose degradation are discussed. The bacteria in biogas fermenters are analyzed, and potential key players for cellulose degradation are pointed out. The principles of their enzyme systems could be used for developing new cellulases for cellulosic biomass as a basic substrate in a future biotechnology.