Chapter 4: Enzymatic Hydrolysis of Lignocellulosic Biomass

Enzymatic hydrolysis is the central technology in a prototypical biochemical conversion process. Preceded by pretreatment and followed by microbial or inorganic catalyst conversion, enzymatic hydrolysis is the process that liberates monomeric sugars from the structural carbohydrates, cellulose, and hemicellulose in lignocellulosic biomass. In order for a biochemical conversion process to be economically viable, enzymatic hydrolysis must produce sugars at high yields and at reasonable conversion rates using a minimum of input energy and chemicals (including hydrolytic enzymes). This chapter reviews research and development efforts to improve enzymatic hydrolysis technology, with particular emphasis on enzyme systems, operation at high solids concentrations, process modeling, and process integration. The development of more active enzyme systems, improved biomass conversion process technology and integration, and more efficient enzyme production systems (as reviewed in Chapter 5) have dramatically improved the economics of enzymatic hydrolysis over the past decade, and commercial biorefineries incorporating enzymatic hydrolysis of lignocellulosic biomass are anticipated within the next few years.