Chemists and engineers taught us how to wring fuels and chemicals out of rock – the word petroleum derives from Latin roots meaning “rock oil”. In the current world, amid concerns that our sources of petroleum are dwindling, we are turning over all stones for suitable alternatives to petroleum. We need to replace an essentially non-renewable resource, petroleum, with renewable fuels and thus make our future sustainable. The major renewable materials on Earth are derived from biological systems that reproduce and replenish themselves. So it is natural to turn to biological systems for producing renewable fuels. This short review focuses on recent advances in engineering organisms and processes to make renewable fuels.
Engineering microbes to produce biofuels. Curr Opin Biotechnol. Nov 9 2010
The current biofuels landscape is chaotic. It is controlled by the rules imposed by economic forces and driven by the necessity of finding new sources of energy, particularly motor fuels. The need is bringing forth great creativity in uncovering new candidate fuel molecules that can be made via metabolic engineering. These next generation fuels include long-chain alcohols, terpenoid hydrocarbons, and diesel-length alkanes. Renewable fuels contain carbon derived from carbon dioxide. The carbon dioxide is derived directly by a photosynthetic fuel-producing organism(s) or via intermediary biomass polymers that were previously derived from carbon dioxide. To use the latter economically, biomass depolymerization processes must improve and this is a very active area of research. There are competitive approaches with some groups using enzyme based methods and others using chemical catalysts. With the former, feedstock and end-product toxicity loom as major problems. Advances chiefly rest on the ability to manipulate biological systems. Computational and modular construction approaches are key. For example, novel metabolic networks have been constructed to make long-chain alcohols and hydrocarbons that have superior fuel properties over ethanol. A particularly exciting approach is to implement a direct utilization of solar energy to make a usable fuel. A number of approaches use the components of current biological systems, but re-engineer them for more direct, efficient production of fuels.