Maximizing light-driven CO2 and N2 fixation efficiency in quantum dot–bacteria hybrids

Integrating light-harvesting materials with microbial biochemistry is a viable approach to produce chemicals with high efficiency from air, water and sunlight. Yet it remains unclear whether all photons absorbed in the materials can be transferred through the material–biology interface for solar-to-chemical production and whether the presence of materials beneficially affects microbial metabolism. Here we report a microbe–semiconductor hybrid by interfacing the CO2- and N2-fixing bacterium Xanthobacter autotrophicus with CdTe quantum dots for light-driven CO2 and N2 fixation with internal quantum efficiencies of 47.2% ± 7.3% and 7.1% ± 1.1%, respectively, reaching the biochemical limits of 46.1% and 6.9% imposed by the stoichiometry in biochemical pathways. Photophysical studies suggest fast charge-transfer kinetics at the microbe–semiconductor interfaces, while proteomics and metabolomics indicate a material-induced regulation of microbial metabolism favouring higher quantum efficiencies compared with biological counterparts alone. Material–microbe hybrids represent a promising strategy for harnessing biochemical reactivity using sunlight, yet little is known about the effect of the interaction on the organism. Here the interface of a CO2- and N2-fixing bacterium to CdTe alters its biochemical pathways, resulting in quantum efficiency close to the theoretical limit.