Sugar transporters from industrial fungi: Key to improving second-generation ethanol production

Second-generation ethanol (2G ethanol) has emerged as a promising alternative to fossil fuels owing to the usage of lignocellulosic biomass (LCB) as feedstock. LCB is mainly composed of cellulose, hemicellulose, and lignin. Biochemical conversion of LCB into ethanol involves four significant steps including pre-treatment, enzymatic hydrolysis, fermentation, and distillation. The major bottleneck to economically feasible 2G ethanol production lies in saccharification and fermentation steps. Lignocellulolytic fungi represent the major commercial sources of biomass-degrading carbohydrate-active enzymes (CAZymes) and possessa complex transporter system that is capable of effectively transporting thesugars released from holocellulosehydrolysates. In this context, an improved understanding of fungal sugar transporters can represent an important strategy to overcome the above-mentioned limitations. With this backdrop, the current paper reviews thesugar transporters from lignocellulolytic fungi, and their importance in 2G ethanol production.