Shining a light on biofuels

Microorganisms that can reduce CO₂ to acetate can be used to generate biofuels. However, CO₂ reduction requires an electron source, usually in the form of H₂, which is costly to produce and difficult to handle. Now, Sakimoto et al. offer an alternative by showing that the acetogenic bacterium Moorella thermoacetica can use cadmium sulfide (CdS) nanoparticles to harvest electrons from sunlight, instead of H₂, to produce acetate. Growing M. thermoacetica in the presence of cadmium and cysteine led to the precipitation of CdS nanoparticles that coated the surface of the bacterium. These nanoparticles enabled the bacterium to use sunlight as an electron source to reduce CO₂, resulting in the production of acetate. Notably, this strategy can sustain bacterial growth and has a high yield, with approximately 90% of the electrons being directed towards acetate production.