Role of Microorganisms in Production of Biofuels

Abstract

AbstractSeveral types of microbes such as whole cells of algae, fungi, yeast, and bacteria are employed to produce biofuel which include several steps such as aerobic and anaerobic fermentation, transesterification, etc. for biofuel production. Present chapter aims to review the wide range of applications of microbes and enzymes used in the pretreatment of diversified lignocellulosic biomass, starchy biomass, and oily biomass having complex structure for the development of a sustainable and economically significant biofuel. Numerous microorganisms have been reported to be involved in biofuel productions such as bioethanol/biobutanol, biogas, biohydrogen, and bioelectricity production. A special focus has been laid on recent microbial resources identified for these purposes from saline and other environmental conditions. Specific applications of microorganisms in pretreatment of solid waste and wastewater are also discussed.Saccharomyces sp., Kluyveromyces sp., Clostridium sp., and Trichoderma sp. have been extensively exploited to obtain a high yield of simpler sugars, lower concentration of inhibitory compounds, and high biofuel yield. Several steps have been taken in recent years to develop genetically engineered microorganisms to enhance saccharification of lignocellulosic biomass, decrease the production of inhibitory sugars, and increase the tolerance level of the fermenting microorganisms for desirable end products.To overcome the challenges associated with municipal solid waste-derived and agricultural feedstocks for enzymatic hydrolysis, potential of diverse microorganisms of biotechnological interest have been identified for fermenting this complex feedstock. This chapter further covers the collective approaches of genetic engineering and metabolic engineering currently being researched to develop mutant and engineered strain of microorganisms for the production of various biofuels (e.g., alcohol, hydrogen, biodiesel, and biogas) from multifarious feedstock materials. The concept of a rational and designed whole-cell catalyst for the production of fourth-generation biofuel and the prospects of microorganisms developed by genetic and metabolic engineering and synthetic biology for second- and fourth-generation biofuel production are also discussed. The chapter concludes with a discussion of metabolic engineering techniques being highly efficient, rapid, precise, and rational when compared to the conventional strategies for development of strain, for instance, mutagenesis. Biosynthetic pathways need to be altered, and it is even possible to introduce and optimize an entirely new pathway in microbes to ensure that we get the final product of our interest from them. There is a need to integrate biofuel fermentation technology and metabolic engineering with an aim to improve metabolism and enhance heterogeneity in gene expression.KeywordsBacteriaAlgaeYeastFungiBiofuelBioethanol