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Researchers Discover Enzyme That Harnesses Light To Make Hydrocarbons (acs.org)
Researchers from the Biosciences and Biotechnologies Institute of the French Alternative Energies and Atomic Energy Commission have discovered a new light-driven enzyme, christened fatty acid photodecarboxylase (FAP), that uses blue light to drive the removal of carboxyl groups from fatty acids to form alkanes or alkenes. Such an enzyme could be used as fuel with no further modification. The Biological SCENE reports: FAP joins a select group of so-called photoenzymes, including DNA-repair enzymes called photolyases, that use light for catalysis on their own rather than functioning as part of a larger complex such as photosystems I or II, which are used by plants and algae for photosynthesis. FAP contains flavin adenine dinucleotide (FAD), which commonly serves as a redox cofactor in biological reactions. In the case of FAP, however, FAD absorbs blue light to reach an excited state that abstracts an electron from the carboxylate group of a C12 to C18 fatty acid, which then decarboxylates to yield an alkane or alkene. The study has been published in the journal Science. Further reading: Ars Technica
Chemist here. The loss of the carboxyl group (the COO part R-COOH, where R is a long chain saturated or unsaturated hydrocarbon depending on source) in fat or vegetable oil acids produces CO2. The resulting hydrocarbons (R-H) will have somewhere between 16 to 18 (plus or minus) carbon atoms and be may be solid or thick oily materials at room temperature, not likely suitable for vehicle fuel. Burning one molecule of a C-18 hydrocarbon will produce 18 molecules of CO2. If you want to use the acids produced from fat or vegetable oils as some kind of fuel, why not just burn the fat and save the expense in time of producing the high molecular weight hydrocarbons from them? For vehicle fuel one would need to crack these hydrocarbons and make branched chain HCs for gasoline, but that's a whole other story.