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Utilization of Lignocellulose-feeding Insects for Viable Biofuels: an Emerging and Promising Area of Entomological Science

  • Jianzhong Sun
  • Xuguo Joe Zhou

Abstract

Most insects are unable to use plant cell walls as their main food sources, but some insects subsist on lignocellulosic biomass from agricultural crops to forest woody substrates as their only foods, such as in the case of termites (all seven families), wood-feeding roaches (Blattidae, Cryptoceridae), beetles (Anobiidae, Buprestidae, Cerambycidae, Scarabaeidae), wood wasps (Siricidae), leaf-shredding aquatic insects (Pteronarcidae, Limnephilidae, Tipulidae), silver fish (Lepismatidae), leaf-cutting ants (Formicidae), etc. Cellulose digestion has been demonstrated in more than 20 families representing ten distinct insect orders, e. g. Thysanura, Plecoptera, Dictyoptera, Orthoptera, Isoptera, Coleoptera, Trichoptera, Hymenoptera, Phasmida, and Diptera. The ability of these insects to feed on wood, foliage and detritus has recently stimulated extensive investigations into the mechanisms of how these insects digest the structural and recalcitrant lignocellulose in their foods. With these studies, scientists would possibly advance biofuel technologies with the discovery of novel lignocellulolytic enzymes and a better understanding of the bioconversion mechanisms that breakdown plant cell walls inside the insect’s gut. Producing monomeric sugars from cellulose or hemicellulose with high yields and low cost is far more difficult than deriving them from sugar- or starch-containing crops. This difficulty is primarily due to a lack of efficient and economic lignocellulolytic enzymes that convert rigid plant cell walls to their monomeric pentose and hexose sugar subunits. However, termites, especially wood-feeding termites (including lower and higher termites), are a unique group of lignocellulose-feeding insects exhibiting incredible wood degradation capabilities, which accomplish lignocellulose digestion using specialized gut physiology, endogenously produced digestive enzymes, and via their specialized association with prokaryotic and eukaryotic gut symbionts. It is believed that the guts of these lignocellulosefeeding insects harbor diverse symbiotic microbes and endogenous enzymes that could be used as a rich source of lignocellulases as well as functional gene resources for improving the conversion of wood or waste plant biomass to valuable biofuels. Recent studies showed that lignocellulose-feeding insects and their symbionts have not only cellulolytic or lignin decomposition activity, but also aromatic hydrocarbon degradation. Thus, as an emerged new area of entomological science, utilization of lignocellulose-feeding insects would be very valuable for viable biofuels production made from lignocellulosic biomass. Clearly, understanding the mechanisms of the biomass digestion in these insect guts could potentially shed light on efficient, low cost, lignocellulose-based biofuel production systems. This review addresses various lignocellulolytic systems, the potential values, various challenges, and opportunities that exist for investigating lignocellulose-feeding insects in biofuels production, as well as possible future research directions.

Keywords

lignocellulose insect lignocellulase lignocellulolytic system biofuels bioreactor 

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Copyright information

© Higher Education Press, Beijing and Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  • Jianzhong Sun
    • 1
  • Xuguo Joe Zhou
    • 2
  1. 1.Jiangsu UniversitySchool of the environmentZhenjiang, JiangsuChina
  2. 2.Insect Integrative Genomics, Department of EntomologyUniversity of KentuckyLexington, KentuckyUSA

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