This is the author accepted manuscript
Biofuels are a commercial reality with ethanol comprising approximately 10% of the US retail fuel market, and biodiesels contributing a little under 5% to the EU retail fuel market. These biofuels are derived from the fermentation of sugars by yeast (ethanol) and from the chemical modification of animal fats and plant oils (biodiesel). However, these biofuel molecules are chemically distinct from the petroleum fuels that they are blended with. Petroleum-based fuels are predominantly composed of alkane and alkene hydrocarbons. These differences impact on fuel properties and infrastructure compatibility resulting in a “blend wall” that – without significant infrastructure realignment and associated costs – limits the use of biofuels. For this reason, there is great interest in biosynthetic routes for alkane and alkene production. Here we will review the known biological routes to alkane/alkene biosynthesis with a focus on bacterial alkane and alkene biosynthetic pathways. Specifically, we will review pathways for which the underlying genetic components have been identified. We will also investigate the development of engineered metabolic pathways that permit the production of alkanes and alkenes that are not naturally synthesized in bacteria (heterologous production) but are suitable for industrial commercial application. Finally, we will highlight some of the challenges facing this research area as it moves from proof-of-principle studies toward industrialization.