Interfacing biosynthetic CdS with engineered Rhodopseudomonas palustris for efficient visible light-driven CO2–CH4 conversion

Abstract

Engineered photosynthetic bacterium Rhodo-pseudomonas palustris is excellent at one-step CO₂ biomethanation and can use near-infrared light sources, overcoming the limitations of conventional photosynthetic systems. The current study constructed a biohybrid system that deposited CdS nanoparticles on R. palustris. This biohybrid system broadens the capture of sustainable solar energy, achieving a 155 nmol·mL⁻¹ biological CH₄ production under full visible light irradiation, 13.4-fold of that by the pure R. palustris. The transcriptome profiles revealed that gene expression related to photosynthetic electron transfer chain, nitrogenase, nanofilaments, and redox stress defense was activated. Accordingly, we attributed the much-enhanced CO₂ biomethanation in the biohybrid system to the remarkable increase in the intracellular reducing power and the stronger rigidity of the cells assisted by photoexcited electrons from CdS nanoparticles. Our discovery offers insight and a promising strategy for improving the current CO₂–CH₄ biomanufacturing system.