REVIEW Methods for discovery and characterization of cellulolytic enzymes from insects

Abstract Cellulosic ethanol has been identified as a crucial biofuel resource due to its sustainability and abundance of cellulose feedstocks. However, current methods to obtain glucose from lignocellulosic biomass are ineffective due to recalcitrance of plant biomass. Insects have evolved endogenous and symbiotic enzymes to efficiently use lignocellulosic material as a source of metabolic glucose. Even though traditional biochemical methods have been used to identify and characterize these enzymes, the advancement of genomic and proteomic research tools are expected to allow new insights into insect digestion of cellulose. This information is highly relevant to the design of improved industrial processes of biofuel production and to identify potential new targets for development of insecticides. This review describes the diverse methodologies used to detect, quantify, purify, clone and express cellulolytic enzymes from insects, as well as their advantages and limitations. Key words biofuels, cellulases, cellulase discovery methods, cellulase substrate, insect digestive fluids, lignocellulosic biomass Insect relevance to lignocellulosic biofuels Current world energy needs demand the development of industrial-scale processes for the sustainable production of fuel from renewable biological resources as economic and environmentally sound alternatives to finite fossil fuels. In the US, lignocellulosic ethanol has been sug-gested as a desirable biofuel, mostly due to its sustain-ability, reduced competition as a food resource, net en-ergy production, and reduced input costs related to pro-duction of ethanol from corn-derived starch (Lynd et al., 1991; McLaughlin et al., 2002; Schmer et al., 2008). Cost-efficient production of ethanol from lignocellulosic biomass is mostly dependent on development of efficient hydrolysis technologies (Sun & Cheng, 2002; Wyman, 2007). Enzymatic degradation of cellulose is considered the hydrolysis method with the greatest potential for im