Biodegradation of Lignocellulosic Biomass and Production of Ethanol Using Potential Microorganisms

Abstract

Plant cells are mainly composed of lignocellulosic material, which includes cellulose, hemicellulose, and lignin (lignocellulosic complex). The hydrolysis of lignocellulose biomass to glucose in the presence of lignocellulolytic enzymes is a major bottleneck in cellulosic biofuel production processes. In nature, microorganisms, especially fungi, are able to degrade the plant cell wall through a set of enzymes acting synergistically. This phenomenon leads to glucose release in a free form. A great challenge is to modify the architecture of the plant cell walls and the ability of the microorganisms to degrade it by modifying their genomes. The ability of biological pretreatment to degrade lignocellulosic materials is due to their highly efficient enzymatic system. Fungi have two types of extracellular enzymatic systems, hydrolytic and ligninolytic systems. The hydrolytic system produces hydrolases that are responsible for polysaccharide degradation and production of sugars. The unique oxidative and extracellular ligninolytic system degrades lignin component and opens phenyl rings. Reducing sugars are further converted into ethanol production using different fermentative microorganisms. In this review, an overview of first- and second-generation ethanol, status of bioethanol production in India, and pretreatment of lignocellulose and its conversion to ethanol has been discussed.