Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/29/2009
Publication Date: 7/1/2010
Citation: Oppert, C., Klingeman, W., Willis, J.D., Oppert, B.S., Jurat-Fuentes, J.L. 2010. Prospecting for Cellulolytic Activity in Insect Digestive Fluids. Comparative Biochemistry and Physiology. 155: 145-154. doi:10.1016/j.cbpb.2009.10.014. Interpretive Summary: In the quest for alternative energy sources, enzymes that are efficient and cost effective in degrading plant biomass are critically needed. Insects are an untapped source for novel cellulolytic enzymes. Using two cellulose substrates, we surveyed insects from 68 species belonging to eight different orders for more efficient cellulolytic enzymes. Enzymes with high activity were found in gut and head tissues and were localized to specific orders, suggesting that some insects may have evolved with increased efficiency to digest plant biomass. These studies are the first step in the identification of enzymes for use by the biofuels industry. In addition, identification of insect cellulolytic systems can lead to novel control strategies for pests of plants and cereals.
Technical Abstract: Efficient cellulolytic enzymes are needed to degrade recalcitrant plant biomass during ethanol purification and make lignocellulosic biofuels a cost-effective alternative to fossil fuels. Despite the large number of insect species that feed on lignocellulosic material, limited availability of quantitative studies comparing cellulase activity among insect taxa limit identification of candidate species for more targeted identification of effective cellulolytic systems. We describe quantitative determinations of the cellulolytic activity in gut or head-derived fluids from 68 phytophagous or xylophagous insect species belonging to eight different taxonomic orders. Activity was determined for two different substrates, carboxymethyl cellulose (CMC) and microcrystalline cellulose (MCC), approximating endo-ß-1,4-glucanase and complete cellulolytic activity, respectively. Highest CMC gut fluid activities were found in Dictyoptera, Coleoptera, Isoptera, and Orthoptera, while highest MCC gut fluid activities were found in Coleoptera, Hymenoptera, Lepidoptera, and Orthoptera. In most cases, gut fluid activities were greater with CMC compared to MCC substrate, except in Diptera, Hymenoptera, and Lepidoptera. In contrast, cellulolytic activity levels in most head fluids were greater against MCC. Our data suggests that a phylogenetic relationship may exist for cellulolytic enzymes in insects and that cellulase activity levels correlate with taxonomic classification, probably evoking differences in plant host or feeding strategies.