School of Minerals Processing and Bioengineering, MOE Key Laboratory of Biohydrometallurgy, Central South University, Changsha, 410083, China.
School of Life Sciences, Central South University, Changsha, 410083, China.
J Hazard Mater. 2019 Apr 15;368:149-155. doi: 10.1016/j.jhazmat.2019.01.031. Epub 2019 Jan 12.
The Cr(Ⅵ) removal way and Cr(Ⅵ) reducing site of Oceanobacillus oncorhynchi W4, a novel Cr(Ⅵ) reducing bacterium, were investigated in this study. Results showed that about 74.2% of Cr(Ⅵ) was removed from solution by growing cells within 72 h. Moreover, heating-killed resting cells had little Cr(Ⅵ) removal capacity, which was significantly lower than that of resting cells, which reached nearly 80% removal rate, suggesting that the way of Cr(Ⅵ) removal mainly relied on biological reduction rather than biosorption. And the Cr(Ⅵ) reduction was found to be significantly enhanced by some electron donors, especially glycerin, which further verified enzyme-mediated biological reduction as the way for Cr(Ⅵ) removal. Experiments of Cr(Ⅵ) removal by permeable cells indicated that there was no significant difference in chromium reduction between the impermeable cells and the permeable cells. The cell envelop fraction had a Cr(Ⅵ) removal rate of 82.9%, apparently higher than cytoplasmic fraction (11.1%), indicating that the cell envelop was the main location for Cr(Ⅵ) reduction, which were further demonstrated by Scanning Electron Microscope and Transmission electron microscopy plus EDS analysis. Furthermore, analysis of X-ray photoelectron spectroscopy manifested that CO, C-OH and C-OC groups on the surfaces played major roles in correlation with chromium species.
本研究考察了新型 Cr(Ⅵ)还原菌海洋芽孢杆菌（Oceanobacillus oncorhynchi W4）的 Cr(Ⅵ)去除途径和 Cr(Ⅵ)还原位点。结果表明，生长细胞在 72 小时内可去除约 74.2%的 Cr(Ⅵ)。此外，加热杀死的休眠细胞去除 Cr(Ⅵ)的能力很低，明显低于休眠细胞，后者的去除率接近 80%，表明 Cr(Ⅵ)的去除方式主要依赖于生物还原而不是生物吸附。并且一些电子供体（特别是甘油）显著增强了 Cr(Ⅵ)的还原，进一步验证了酶介导的生物还原是 Cr(Ⅵ)去除的途径。透性细胞去除 Cr(Ⅵ)的实验表明，不透性细胞和透性细胞在铬还原方面没有显著差异。细胞包膜部分的 Cr(Ⅵ)去除率为 82.9%，明显高于细胞质部分（11.1%），表明细胞包膜是 Cr(Ⅵ)还原的主要部位，这进一步通过扫描电子显微镜和透射电子显微镜加 EDS 分析得到证实。此外，X 射线光电子能谱分析表明，表面的 CO、C-OH 和 C-OC 基团在与铬物种的相互作用中起主要作用。
