Lignocellulosic ethanol production from cotton stalk: an overview on pretreatment, saccharification and fermentation methods for improved bioconversion process

Cotton stalk is the most widely generated agricultural residue with lower economic importance, and can be employed as a feedstock in lignocellulosic biorefinery for the manufacture of bioethanol and other value-added bioproducts. Cotton stalk possesses high holocellulose content, which can be saccharified to various fermentable sugars for bioethanol production. However, the occurrence of high amount of lignin in cotton stalk renders it an inferior substrate for bioethanol production. Selection of suitable pretreatment process can improve digestibility of cotton stalk and hence higher sugar concentration on subsequent enzymatic saccharification. Furthermore, fermentation of hexose and pentoses sugars to ethanol requires robust microbial strains and efficient fermentation methods. Therefore, the major hindrance in commercializing lignocellulosic ethanol from cotton stalk is to develop an effective combination of pretreatment, saccharification, and fermentation methods thereby making the whole bioconversion process economically viable. This review paper discusses various previously investigated pretreatment, acid and/or enzymatic saccharification, and fermentation methods for cotton stalk-to-lignocellulosic ethanol production . Finally, it also discusses the major barriers in bioethanol fermentation strategies, and as well future perspectives to overcome these issues.