Engineering Ligninolytic Consortium for Bioconversion of Lignocelluloses to Ethanol and Chemicals

Background: Rising environmental concerns and recent global scenario of cleaner production and consumption are leading to the design of green industrial processes to produce alternative fuels and chemicals. Although bioethanol is one of the most promising and eco-friendly alternatives to fossil fuels yet its production from food and feed has received much negative criticism.

Objective: The main objective of this study was to present the noteworthy potentialities of lignocellulosic biomass as an enormous and renewable biological resource. The particular focus was also given on engineering ligninolytic consortium for bioconversion of lignocelluloses to ethanol and chemicals on sustainable and environmentally basis.

Methods: Herein, an effort has been made to extensively review, analyze and compile salient information related to the topic of interest. Several authentic bibliographic databases including PubMed, Scopus, Elsevier, Springer, Bentham Science and other scientific databases were searched with utmost care, and inclusion/ exclusion criterion was adopted to appraise the quality of retrieved peer-reviewed research literature.

Results: Bioethanol production from lignocellulosic biomass can largely satisfy the possible inconsistency of first-generation ethanol since it utilizes inedible lignocellulosic feedstocks, primarily sourced from agriculture and forestry wastes. Two major polysaccharides in lignocellulosic biomass namely, cellulose and hemicellulose constitute a complex lignocellulosic network by connecting with lignin, which is highly recalcitrant to depolymerization. Several attempts have been made to reduce the cost involved in the process through improving the pretreatment process. While, the ligninolytic enzymes of white rot fungi (WRF) including laccase, lignin peroxidase (LiP), and manganese peroxidase (MnP) have appeared as versatile biocatalysts for delignification of several lignocellulosic residues. The first part of the review is mainly focused on engineering ligninolytic consortium. In the second part, WRF and its unique ligninolytic enzyme-based bio-delignification of lignocellulosic biomass, enzymatic hydrolysis, and fermentation of hydrolyzed feedstock are discussed. The metabolic engineering, enzymatic engineering, synthetic biology aspects for ethanol production and platform chemicals production are comprehensively reviewed in the third part. Towards the end information is also given on futuristic viewpoints.

Conclusion: In conclusion, given the present unpredicted scenario of energy and fuel crisis accompanied by global warming, lignocellulosic bioethanol holds great promise as an alternative to petroleum. Apart from bioethanol, the simultaneous production of other value-added products may improve the economics of lignocellulosic bioethanol bioconversion process.