Deciphering interfacial photoelectron transfer in a Thiobacillus denitrificans-CdS Biohybrid for efficient vanadate...

Vanadium (V) is a re-emerging environmental hazard currently. Microbial vanadate [V(V)] reduction is a key process for its detoxification, which is commonly driven by electron-donor provided chemical energy. The contribution of ubiquitous solar energy for V(V) bioreduction remains largely unknown. This study investigated V(V) removal in an artificial photosynthetic biohybrid system for promising utilization of solar energy. The synthesized Thiobacillus denitrificans-CdS biohybrid under light achieved a V(V) removal efficiency of 96.3 ± 2.7% within 4 days, along with biomass growth. Characterizations including XANES and EXAFS verified that V(V) was reduced to insoluble tetravalent V [V(IV)] oxide precipitates containing V=O and V-O on the biohybrid interface. Crucially, the in situ precipitated V(IV) narrowed the semiconductor bandgap and suppressed carrier recombination, continuously boosting the photocurrent density for enhanced V(V) removal. Biochemical quantification and inhibitor tests confirmed the involvement of cellular compounds, especially cytochrome c in electron transfer, eventually contributing to V(V) reduction. Transcriptomic analysis and gene transcription quantification suggested that genes such as narG and norB were also potentially associated with V(V) reduction. This study employed solar energy to sustainably power non-photosynthetic microorganism to reduce V(V), providing previously unrecognized understanding of V geochemistry and promising novel strategy for V remediation.