ABSTRACT

The first generation biofuels such as bioethanol and biodiesel are projected as suitable alternatives to conventional petroleum-based fuels; however, their market penetration is still too low due to several technical and economic barriers. The realization of advanced biofuels beyond ethanol has led to the discovery of various new metabolic pathways among different microbial hosts. It is observed that most of the fermentative microorganisms have a natural tendency to produce butanol, propanol, or other alcohols that can serve as potential biofuels. Also, several bacterial species can generate gaseous biofuels like hydrogen or methane. Similarly, certain photosynthetic microorganisms tend to store lipids or carbohydrates, which can either be extracted or used as a feedstock for biofuel generation. The knowledge of the metabolic pathways is thus essential to enhance the yield of the desired product and to improve the process efficiency. Furthermore, once known, these pathways can be redefined and reconstructed into suitable hosts using various metabolic engineering approaches. This chapter provides an insight into the various biochemical pathways that are exploited currently for biofuel production. In addition, the possible process and genetic engineering strategies to enhance the overall yield of the specific product of interest are discussed.