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 Chlorella variabilis FAP ( Cv FAP) can convert n -octanoic acid in vitro four times faster than n -hexadecanoic acid, its best substrate reported to date. In vivo, this translates into a Cv FAP-based production rate over 10-fold higher for n -heptane than for n -pentadecane. Time-resolved spectroscopy and molecular modeling demonstrate that Cv FAP’s high catalytic activity on n -octanoic acid is, in part, due to an autocatalytic effect of its n -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.

Catalytic Mechanism of Fatty Acid Photodecarboxylase: On the Detection and Stability of the Initial Carbonyloxy Radical Intermediate

“…Presently, there are only three known distinct types of natural photoenzymes. Of these, fatty acid photodecarboxylase (FAP) is a flavoenzyme that transforms fatty acids into hydrocarbons and CO 2 with high (70–80 %) photochemical quantum yield (QY) [6–7] . Since its discovery in 2017, [6] FAP has become the subject of intense research, aiming to both unravel its fundamental mechanism [6,8–10] and explore its potential as a template for novel green chemistry photocatalytic reactions [11] .…”

“…Of these, fatty acid photodecarboxylase (FAP) is a flavoenzyme that transforms fatty acids into hydrocarbons and CO 2 with high (70-80 %) photochemical quantum yield (QY). [6][7] Since its discovery in 2017, [6] FAP has become the subject of intense research, aiming to both unravel its fundamental mechanism [6,[8][9][10] and explore its potential as a template for novel green chemistry photocatalytic reactions. [11] These research lines are intertwined, as understanding the mechanism is essential for the design of derived photocatalysts.…”

Alka(e)nes contribute to membrane lipid homeostasis and resilience of photosynthesis to high light in cyanobacteria

“…As photosynthetic microorganisms, microalgae also harbor a distinctive pathway for alka(e)ne synthesis (9). The discovery of fatty acid photodecarboxylase (FAP) in green microalgae (10) has enriched our repertoire of alka(e)ne-forming enzymes because of the unique photocatalytic process of FAP, which converts free fatty acids (FFA) to alka(e)nes using light in the range 350-530 nm (11,12). FAP belongs to an algal-specific clade of glucose methanol choline (GMC) oxidoreductase family and phylogenetic analysis showed that this photoenzyme is conserved in photosynthesis-retained algal lineages (13).…”