An outer membrane photosensitized Geobacter sulfurreducens-CdS biohybrid for redox transformation of Cr(VI) and tetracycline

Abstract

Microbe-photocatalyst biohybrids, integrating the optimal attributes of whole-cell catalysts and nanometer photocatalysts, have emerged as a promising strategy for environment-associated applications. However, few such biohybrids have been tested for complex pollution systems. Herein, we constructed an outer membrane photosensitized Geobacter sulfurreducens (G. sulfurreducens)-CdS biohybrid, which enabled to generate stronger photocurrent in response to irradiation and meanwhile achieved an significant promotion for the redox transformation of Cr(VI) and tetracycline compared with that of bare G. sulfurreducens or CdS counterparts. Further analysis revealed that the outer membrane played a significant role in photoelectron transfer. Differential pulse voltammetry (DPV) tests demonstrated that CdS enhanced the catalytic activity of C-type cytochromes on the outer membrane under irradiation, resulting in the increase of electron-hole pairs separation efficiency. The possible degradation pathway of tetracycline was proposed based on determined intermediates, whose toxicities were well evaluated. Importantly, the toxicity of the final detected intermediates was apparently decreased. Overall, this work aims to explore the working mechanisms of the novel G. sulfurreducens-CdS biohybrid system and opens up a new avenue to purifying combined wastewater by microbe-photocatalyst biohybrids.

Keywords: Cr(VI) reduction; Electron transfer; G. sulfurreducens-CdS biohybrid; Tetracycline oxidation.