Lignocellulosic biomass and microbial genome engineering for sustainable ethanol production: An overview

In the last few decades, various scientific and technological developments in the fermentation process have significantly contributed to the progress of the ethanol industry worldwide. These major contributions have expanded our view about fermentation in first- and second-generation ethanol production. Currently, advanced technologies are available to produce ethanol from lignocellulosic biomass (LCB) such as sugarcane, sugar beet, corn, and other feedstocks. The LCB is composed of various 5- (e.g., arabinose and xylose) and 6- (e.g., glucose, galactose, and mannose) carbon sugars. The efficiency of ethanol processing needs to be enhanced further to meet the Sustainable Development Goals (SDGs) of the United Nations. Conventional genome modification techniques like mutation and selection are being extensively employed to over-produce ethanol through microbial fermentation. In addition to conventional techniques, this chapter evaluates the potential application of clustered regularly interspaced short palindromic repeats (CRISPR) associated genome engineering of potential microbes for enhanced ethanol efficiency. The CRISPR/Cas9 is a groundbreaking technology and has engineered microbial genomes for desirable traits in an efficient and advanced way. Genome alterations of various microbes including bacteria, fungi, algae, and Saccharomyces cerevisiae have been accomplished through this technique for various applications. In this chapter, we summarized the major discoveries of CRISPR/Cas9-mediated genome editing in microorganisms and deliberate how these discoveries can be utilized for the sustainability and enhancement of ethanol production.