Response of Bacillus vallismortis sp. EPS to exogenous sulfur stress/ induction and its adsorption performance on Cu(II)
2020
Li, Qiuhua | Song, Weifeng | Sun, Mengge | Li, Jiayao | Yu, Zefeng
The chemical composition of EPS (Extracellular Polymeric Substances) produced by Bacillus vallismortis sp. and its adsorption performance on typical heavy metal were studied under Na₂S stress/induction at different concentrations. Its structure was characterized by three-dimensional fluorescence spectrogram (3D-EEM), infrared spectrum (FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed that, when the Na₂S stress/induction intensity was 20 mg/L, the protein concentration was nearly doubled compared with Control-EPS (EPS produced by Bacillus vallismortis sp. without exogenous sulfur stress); furthermore, the 3D-EEM results also demonstrated that there was an increase in the protein content, with the –SH content reaching 154.36 μmol/L, which was 48.2% higher than before stress (104.15 μmol/L). Under this condition, S-EPS (EPS produced by Bacillus vallismortis sp. stressed by exogenous sulfur) exhibited the best adsorption effect on Cu(II), with the theoretical maximum adsorption capacity reaching 1428.57 mg/g EPS. FTIR and XPS analyses revealed that the –SH, CO, N–H played a major role in the adsorption of Cu(II); among those, –SH played a key role. Moreover, the adsorption capacity of Cu(II) by S-EPS was correlated with the content of sulfhydryl protein; indeed, the exogenous sulfur stress/induction can effectively regulate the chemical composition of EPS and improve its adsorption performance, which can be crucial in the prevention and control of heavy metal pollution.
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