Ligninases and Glycosyl Hydrolases in Developing a cellulosic Bioethanol Industry

Abstract

The lingocellulosic wastes are produced by industries, forestry, agriculture and municipalities. The accumulation of these wastes result in several environmental problems, health issues and safety hazards. These lingocellulosic wastes are economically attractive materials for cellulosic bioethanol production because of the large amount of potential sugar for fermentation and bioenergy production. However, the conversion of lignocellulosic biomass is challenged by its recalcitrant structure. For efficient conversion to bioethanol, it is important to study the composition of the raw lingocellulosic residues and devise appropriate delignification and saccharification strategies. The discovery of lignin degrading enzymes (lignin peroxidases, manganese peroxidases, versatile peroxidases and laccases) in cultures of the white rot fungi marked the beginning of the development of enzymatic systems for applied biomass delignification. Degradation of resulting cellulosic biomass is performed by a mixture of hydrolytic enzymes collectively known as glycosyl hydrolases (cellulases and hemicellulases), which act in a synergistic manner in biomass-degrading microorganisms. In comparison with conventional physico-chemical processes, enzymatic delignification and saccharification treatments of lignocellulosic materials are advantageous due to their specificities, low energy requirement, mild operational conditions, absence of substrate loss due to chemical modifications, and no byproduct formation. This review examines what is currently known regarding recent enzymatic technologies for delignification and saccharification of lignocellulosic materials that are used in production of second generation bioethanol.