Initial Approaches to Artificial Cellulase Systems for Conversion of Biomass to Ethanol

摘要

The process of converting low-value biomass to ethanol via fermentation depends keenly on the development of economic biocatalysts to achieve effective depolymerization of the cellulosic content of biomass. This process has few features in common with contemporary large-scale uses of cellulases, such as food processing and detergent augmentation. Cellulase preparations used in an ethanol-from-biomass process must hydrolyze crystalline cellulose completely, operate effectively at mildly acidic pH, withstand process stress, and they need not be derived from microorganisms that are generally recognized as safe (GRAS). Furthermore, the ideal cellulase complex used in biomass processing should be highly active on the intended feedstock and obtainable at the lowest possible cost. Clearly, the ability to "engineer" cellulase systems in anticipation of each application is key to successful optimization and commercialization. To achieve this goal, we are collaborating with other researchers to purify individual cellulase enzymes and their genes from a variety of bacteria and fungi. We are also comparing purified cellulases, both individually and in mixtures, using key criteria, to design and assemble optimized, use-specific, artificial cellulase systems that can be produced by recombinant host microorganisms on an industrial scale. This paper describes both strategies and progress to date.