A Newly Identified Photoenzyme Helps Algae Pump Out Fuel

The finding could lead to a new way of producing “green” alternatives to fossil fuels.

Feb 1, 2018
Katarina Zimmer

GREEN MACHINES: One species of Chlorella algae uses a photoenzyme to convert fatty acids into fossil fuel–like hydrocarbons.LAURENCE GODART


The paper
D. Sorigué et al., “An algal photoenzyme converts fatty acids to hydrocarbons,” Science, 357:903-907, 2017.

Green Fuel
Finding enzymes in nature that convert plant oils into fossil fuel–like hydrocarbons could lead the way toward harnessing new energy sources. After observing that the freshwater alga Chlorella variabilis can convert fatty acids into alkanes or alkenes, a team of researchers from France decided to investigate how it accomplished this feat.

Fatty Acid Engine
The researchers’ assay detected a particularly abundant hydrocarbon-forming enzyme that appears to be located in C. variabilis’s chloroplast membrane, says study leader Frédéric Beisson, who researches algae metabolism at the Institute of Biosciences and Biotechnologies at Aix-Marseille University. So they expressed the protein in E. coli to test its function, and used mass spectrometry to get a close look at its mechanism of action. The enzyme turned out to be capable of converting a range of fatty acid substrates into hydrocarbon chains, but only under blue light.

A Rare Find
The researchers were surprised to find that the new enzyme, dubbed fatty acid photodecarboxylase, captures energy directly from light, in contrast to enzymes whose expression is regulated by light. “It wasn’t something we were expecting,” remarks Beisson. Additionally, unlike enzymes that need just a flash of light to become active, the new enzyme only works under continuous light, making it an addition to a mere handful of known “photoenzymes.”

Getting Into Gear
The production of hydrocarbons is a well-studied process in algae, Günther Knör, a chemist at Johannes Kepler University in Austria, writes to The Scientist in an email. But he thinks that photoenzymes could be used to more efficiently produce hydrocarbons in light-driven artificial systems in the near future: “This would be a breakthrough for solar fuel generation inspired by nature.”