Autocatalytic effect boosts the production of medium-chain hydrocarbons by fatty acid photodecarboxylase.

Abstract

Ongoing climate change is driving the search for renewable and carbon-neutral alternatives to fossil fuels. Photocatalytic conversion of fatty acids to hydrocarbons by fatty acid photodecarboxylase (FAP) represents a promising route to green fuels. However, the alleged low activity of FAP on C2 to C12 fatty acids seemed to preclude the use for synthesis of gasoline-range hydrocarbons. Here, we reveal that <i>Chlorella variabilis</i> FAP (<i>Cv</i>FAP) can convert <i>n</i>-octanoic acid in vitro four times faster than <i>n</i>-hexadecanoic acid, its best substrate reported to date. In vivo, this translates into a <i>Cv</i>FAP-based production rate over 10-fold higher for <i>n</i>-heptane than for <i>n</i>-pentadecane. Time-resolved spectroscopy and molecular modeling demonstrate that <i>Cv</i>FAP's high catalytic activity on <i>n</i>-octanoic acid is, in part, due to an autocatalytic effect of its <i>n</i>-heptane product, which fills the rest of the binding pocket. These results represent an important step toward a bio-based and light-driven production of gasoline-like hydrocarbons.