The search for increased efficiency and lower costs for second-generation (2G) bioethanol production is generated by concerns regarding food safety and crop expansion, because the first generation of this fuel competes with production of food for consumption. There is also interest in decreasing associated greenhouse gas emissions and dependence on fossil fuels. However, processing 2G ethanol is expensive, inhibiting scale up of production. To produce this second-generation fuel, lignocellulosic materials need to be pretreated and hydrolyzed such that the fermentable sugars can be released from their polysaccharides. This biomass requires efficient enzymes to cleave cellulose and hemicellulose fractions (and sometimes pectin as well) into oligosaccharides (e.g. cellobiose) and monosaccharides (pentoses and hexoses) that depend on yeasts to convert them into ethanol via alcoholic fermentation. Fortunately, herbivorous insects are a potential source of enzymes and microorganisms to perform these functions, because they consume the carbohydrates from the lignocellulosic biomass. This review addresses various strategies for the bioprospection of enzymes (either endogenous or from insect microbiomes) and/or insect isolated yeasts; the efficiency of xylose and cellobiose metabolism of those microorganisms; successful experiments with such biocatalysts; and in particular, the economic impact of bioprospected enzymes and microorganisms exploited for 2G ethanol production.
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