Cellulolytic microorganisms: Diversity and role in conversion of rice straw to bioethanol

Abstract

Lignocellulosic biomass is considered to be an inexhaustible biopolymer known to mankind. For the successful exploitation of lignocellulosic biomass, such as rice straw, as a substrate for the production of industrially significant value-added products, such as bioethanol, its conversion into fermentable sugars, sugar acids and phenolics is the most imperative step. Enzymatic hydrolysis of lignocelluloses is performed by cellulases, a complex enzyme system comprising endo-1,4-β-D-glucanase, exo-1,4-β-D-glucanase and β-D-glucosidase. Cellulases are produced by a diverse range of microorganisms, including bacteria, fungi, actinomycetes, algae, insects and mollusks. However, the cost of cellulase is a major economic barrier for ethanol production. To economize the ethanol production process for its successful utilization at the industrial scale, genetic improvement of microorganisms, and other industrially relevant strategies of enzyme production and recycling need to be adopted.