Changes in Desulfovibrio desulfuricans sub sp EPS components and adsorption performance under exogenous sulfur induction and its mediation role in the biosynthesis of ZnS QDs

Sulfate Reducing Bacteria(SRB) can remove heavy metal ions by producing metal sulfide precipitation, which has aroused the research interest of scholars recently. For SRB, exogenous sulfur is one of the most important nutrients, however, there are few reports about the impact of exogenous sulfur on SRB, especially its EPS. Here, we investigated the inducible effect of sulfur sources (Na2SO4, Na2SO3, and Na2S2O3 center dot H2O) on EPS production from SRB for the first time. The results found that exogenous sulfur can significantly increase the production of EPS, especially protein. The increased functional groups(C-O/C-N, C=N) in the protein are favorable to adsorption of more heavy metals. Moreover, S2- was added to the system after adsorption of Zn(II) for the biosynthesis of ZnS QDs from the resource recovery point. The experiments and tests showed the yield of cubic beta-ZnS QDs correlated with the amount and adsorption performance of EPS. The PL spectrum of EPS present red-shifted and enhanced antibacterial properties due to the adhesion of EPS to ZnS QDs, the basic amino acid His in EPS played an important role in the adsorption of Zn(II) and the nucleation of ZnS QDs. This research brings new horizons for using EPS to treatment heavy metal wastewater and resource recycling.