Biosynthetic pathways involved in the synthesis of next-generation biofuels in microbial cells

Diminishing fossil resources and the environmental risks associated with the use of fossil fuels have raised concerns about the production of future sustainable fuels. Fatty acid-derived advanced biofuels (alkanes and alkenes) synthesized from microbial species may serve as appealing alternatives to overcome energy-related issues. Alka(e)nes of medium chain length are major constituents of gasoline, diesel and jet fuel and are produced naturally by different microbial genera as a part of their cellular metabolism. The present review aims to extend the existing knowledge toward the different biosynthetic pathways that have been reported among the different microbial species for the production of alka(e)nes of various carbon lengths. This study also provides deep insight into the possibility of enhancing the production of next-generation biofuels through metabolic engineering of different pathways in heterologous hosts. The introduction of multiple gene/enzyme cascades and their compartmentalization in different organelles will further facilitate the maximum production of mimic fuels, which in turn will reduce the dependence on current transportation fuels.