Microbes, Environment and Human Welfare

초록

Energy insecurity due to the rapid depletion of fossil fuels and environmental pollution caused by the combustion of fossil fuel are two major concerns encountered today. Production of cleaner and alternative fuels from renewable biomass feedstock could be a sustainable way to offset the fossil fuel exhaustion and greenhouse gas emission. Several approaches to produce biofuels from sustainable biomass and biological waste have been conducted using versatile microorganisms. For example, several bacteria such as Zymomonasmobilis, Bacillus cereus, and yeasts such as Saccharomyces cerevisiae can convert various sugars from agricultural wastes, organic wastes, microalgal biomass into alcohols. In addition to sugars, amino acids can also be converted into higher alcohols. Whereas, microalgal cells can generate a substantial amount of storage lipid which can be converted into biodiesel via transesterification. Besides liquid biofuels, gaseous biofuels such as biohydrogen (bioH2) and biomethane (bioCH4) are produced from renewable biomass feedstock via acidogenic anaerobic fermentation and anaerobic digestion, respectively. Fermentative bioH2 production results from the diverse metabolic activities of several fermentative microorganisms and is always accompanied by the production of short-chain fatty acids (SCFAs). Anaerobic digestion, on the other hand, involves several distinct stages: hydrolysis, i.e., breakdown of complex biological polymer into monomers such as monosaccharides, amino acids, and fatty acids; acidogenesis, in which monomers are converted into SCFAs (C1-C8), alcohols, CO2 and H2; acetogenesis, involving conversion of SCFAs and alcohols into acetate and ultimately the methanogenesis, in which a special group of microorganisms called methanogens convert acetate or CO2 and H2 into CH4. This chapter reviews the various aspects of biofuels production by microorganisms from renewable biomass and the impending requirement of addressing the challenges with possible future directions