Biofuel production from renewable feedstocks: Progress through metabolic engineering

The rising demand for energy to meet the needs for the growing population has instigated the extensive use of fossil fuels. This increasing dependence on fossil fuel consumption is projected to affect the global climate stability, and hence it has become imperative to develop sustainable routes for the generation of clean energy from renewable feedstocks to support the continued prosperity and economic growth of the world. Photosynthetic feedstocks such as lignocellulosic wastes, algal biomass, etc. have huge potential for the production of biofuels and value-added biochemicals. However, release of fermentable sugars from these organic sources is a major hindrance because of its recalcitrant nature, which affects the overall production cost. In this regard, advances in metabolic engineering of plants and microbial systems have resulted in the easier release and fermentation of sugars for bioconversion to fuels and chemicals. The availability of genomic sequences of microbial species and the development of genome-scale metabolic models have aided in the fast-track reconstruction of cellular metabolism, which can assist in metabolic engineering. “Omics”-approaches such as genomics, transcriptomics, proteomics, and metabolomics can provide researchers new insights into the gene regulation and coordinated cellular activities that govern the physiological flexibility and metabolic adaptation of the hosts. Furthermore, metabolic engineering approaches such as overexpression of heterologous genes, blocking competitive pathways, as well as modifying the rate-limiting enzymes have accelerated the quest to uncover the molecular mechanisms as well as modify pathways associated with biofuel production. Some of the conventional biofuels produced from engineered plants and microbes are bioethanol and biodiesel. This chapter provides a brief overview of the worldwide scenario of biofuel production and the advancements made in their synthesis using metabolic engineering.