Harnessing Solar Energy for the Photocatalytic Reduction of Hexavalent Chromium: A High-Performance <i>Yarrowia lipolytica</i>–CdS Biohybrid System

Photosynthetic semiconductor biohybrids, which combine the light-harvesting capacity of semiconductors and catalytic activity of whole-cell microorganisms, show substantial potential for advancing bioremediation technology. However, few yeast-based biohybrid systems for pollutant removal were reported. In this study, we have constructed a whole-cell biohybrid system based on <i>Yarrowia lipolytica</i> featuring <i>in situ</i> synthesized biocompatible cadmium sulfide (CdS) nanoparticles (NPs) for the photocatalytic reduction of hexavalent chromium [Cr(VI)] under UV irradiation. The integration of these CdS NPs onto the surface of modified <i>Y. lipolytica</i> cells endowed the system with excellent photocatalytic performance, achieving 100% Cr(VI) reduction within 2 h. The system exhibited a higher kinetic constant (0.03 min^-1). In the trapping experiments, the reactive oxygen species (ROS) generated photochemically, specifically the superoxide anion (•O^2-), which were identified as crucial mediators that facilitate the reduction of Cr(VI). The enhanced activity of the <i>Y. lipolytica</i>-CdS biohybrid was attributed to efficient electron transfer. Additionally, through transcriptome analysis, we found that the differentially expressed genes are associated with membrane transport, oxidation-reduction process, energy metabolism, and electron transfer. This whole-cell biohybrid catalytic strategy holds promise as an innovative approach for the reduction of Cr(VI) and has the potential to enhance our understanding of the interactions among light, inorganic material, and microorganisms.