Insights into the EPS production and distribution of planktonic and attached Sulfobacillus thermosulfidooxidans cells during bioleaching

Abstract

Bacterial leaching can effectively promote the bioleaching of chalcopyrite by secreting extracellular polymeric substances (EPS). In this study, the production and distribution of EPS on the surface of planktonic and attached cells of Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans) during the process of chalcopyrite concentrate bioleaching were observed in situ using Field emission scanning electron microscope (FE-SEM) and Confocal laser scanning microscope (CLSM). The TOC content and key components of EPS were extracted during the chalcopyrite bioleaching process. Moreover, the main functional groups of extracellular polymorphs were identified through Fourier transmission-infrared spectroscopy (FT-IR). The results showed a similar trend in the evolution of EPS content in planktonic and attached cells. However, the EPS content secreted by the cells attached was more than that of planktonic cells during the entire process of bioleaching. Furthermore, the results of FE-SEM indicated that the EPS secreted by the attached cells is thicker and stickier, with better adsorption performance. The FT-IR spectrum analysis revealed that the O–H, C–H, and CO bonds are the main functional groups of EPS. This work further clarifies the role of EPS in the bioleaching process.