New trends in application of nanotechnology for the pretreatment of lignocellulosic biomass

Pretreatment is an inevitable step in the bioethanol / biochemicals production process in which lignocellulosic biomass (LB) is converted to fermentable sugars. It has a large impact on process cost, constituting approximately 40% of total processing cost of bioethanol or biochemical production. Several physical, chemical, physicochemical, and biological pretreatment approaches are available but there are certain limitations to the use of all of these methods on a large scale, which mainly include high processing costs, the generation of toxic inhibitors, and the detoxification of the inhibitors generated. These limitations collectively restrict the use of the existing methods and warrants for the development of a novel, efficient, cost‐effective, and ecofriendly approach for the pretreatment of LB. In this context, nanotechnology‐based pretreatment methods, involving the use of various nanomaterials, have been proposed. The smaller size of nanomaterials makes them more efficient in penetrating the cell walls of LB and hence such nanomaterials can readily interact with the lignocellulosic components at low severity to release carbohydrates to be used for bioethanol and / or biochemical production. This review provides a brief description of various existing pretreatment methods and their advantages and disadvantages. It also presents a critical overview of the application of various nanotechnological methods in the pretreatment of different lignocellulosic substrates.