昆虫与生物质能源利用：一个新的交叉学科前沿
Cellulolytic insects and their potentials for viable biofuels: a new frontier discipline in Entomology and Bioengineering
孙建中* 陈春润
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作者单位：江苏大学环境学院，江苏大学生物质能源研究所，镇江 212013
中文关键词：利用木质纤维素的昆虫，生物质，生物质能源，生物催化与生物降解，食木白蚁
英文关键词： lignocellulose-feeding insects, biomass, biofuels, biocatalysis and biodegradation, wood-feeding termites
中文摘要：
昆虫与生物质能源利用密切相关。这些昆虫包括白蚁类、甲虫类、树蜂类、食叶类水生昆虫、衣鱼类、大蚊类等。它们能在树木、枯枝以及落叶上生活，并具有了相当可观的降解和转化木质纤维素的能力，是自然界中协助进行碳循环的一类重要节肢动物。近几年来，这些昆虫独特的肠道消化能力以及它们的生物质催化转化系统已引起了科学家和研究人员的极大兴趣，希望能通过发现新的降解木质纤维素的酶及酶系统、掌握相关的这些酶的表达和其功能控制基因、并能解开昆虫肠道的消化及其相关机制的谜;更高效的降解和转化植物细胞壁中的碳水化合物并用来生产不同种类的生物能源或生物基材料。目前，对这类昆虫高效降解木质纤维素能力的认识和相关降解机制的研究已发展成为一个与生物质能源应用密切相关的新兴研究领域，成为新的交叉学科前沿。本文将简要讨论这类昆虫消化木质纤维素的几种不同作用机制、共生微生物与昆虫所产生的不同木质纤维素酶以及相互间的协同作用的基础上，还探讨了当前第二代生物质能源研究与开发中所面临的主要挑战、消化木质纤维素类昆虫,特别是白蚁所处的独特地位、潜在的科学和应用价值，以及今后的主要研究方向。
英文摘要： 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. 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, cellulolytic insects, especially wood-feeding termites, are a unique group of lignocellulose-feeding animals 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 lignocellulose-feeding 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. Thus, as a frontier and emerged discipline crossing entomology and bioengineering 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 mini-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.