Anaerobically photoreductive degradation by CdS nanocrystal: Biofabrication process and bioelectron-driven reaction coupled with Shewanella oneidensis MR-1

Electrochemically active bacteria (EAB) have attracted great attention in the pollutant biodegradation due to its unique extracellular reduction capacity. But the reduction ability of biogenic electron is insufficient to achieve degradation of many pollutants. Thus, in the present study, Shewanella oneidensis MR-1 was firstly employed to biofabricate visible light-responsive CdS nanocrystals. A bio-photoelectric reductive degradation system (BPRDS) which established by combining S. oneidensis MR-1 and self-synthesized CdS achieved efficient degradation of trypan blue under photoexcitation. Chemical analyses revealed that the cleavage of azo bonds resulted in the decolorization. Blocking of transmembrane electron transfer significantly decreased the decolorization efficiency of BPRDS. After incubating for 5 h, the removal of trypan blue in BPRDS inoculated with ΔmtrA, ΔmtrB, ΔmtrC/omcA, or ΔcymA mutants reduced by 16.46 %, 27.88 %, 25.03 %, and 57.9 %, respectively, compared with wild-type strain inoculated, which indicated that biogenic electron produced by anaerobic respiratory of S. oneidensis MR-1 acted as a hole scavenger and maintained the anaerobic photoexcitation of CdS in BPRDS. Photoexcitation was essential for the BPRDS. This work may provide a new strategy for anaerobic remediation of organic contaminants and be beneficial for the better understanding about anaerobic photodegradation mechanism.