Semiconductor augmented hydrogen and polyhydroxybutyrate photosynthesis from Rhodospirillum rubrum and a mechanism study†

Photosynthetic biohybrid systems based on purple bacteria and semiconducting nanomaterials are promising platforms for sustainable solar-powered chemical production. However, these biohybrid systems have not been fully developed to date, and their energy utilization and electron transfer mechanisms are poorly understood. Herein, a Rhodospirillum rubrum–CdS biohybrid system was successfully constructed. The photosynthetic activity and photoelectrochemical properties of the biohybrid system were analyzed. Chromatographic and spectroscopic studies confirmed that the metabolic activities of R. rubrum cells were effectively augmented by surface-deposited CdS nanoparticles and validated with increased H₂ evolution, polyhydroxybutyrate (PHB) production and solid biomass accumulation. The energy consumption and metabolic profiles of the R. rubrum–CdS biohybrid system exhibited a growth phase-dependent behaviour. A photoelectrochemical study confirmed that light-excited electrons from CdS enhanced the photosynthetic electron flow of R. rubrum cells. Monochromatic light-modulated photoexcitation of the biohybrid system was utilized to explore interfacial electron transfer between CdS and R. rubrum cells, and the results showed that CdS enhanced the utilization of blue light by R. rubrum cells. This work investigated the feasibility and prospects of utilizing R. rubrum in semi-artificial photosynthesis of valuable products and offers insights into the energy utilization and the electron transfer mechanism between nanomaterials and purple bacteria.