球形红细菌对六价铬的生物还原与三价铬积累

Biological reduction of hexavalent chromium and trivalent chromium accumulation by Rhodobacter sphaeroides

目的研究球形红细菌将高毒性六价铬Cr(Ⅵ)还原为低毒性三价铬Cr(Ⅲ)的最适条件及其机制。方法通过研究不同理化因素对球形红细菌还原Cr(Ⅵ)的影响,确定还原Cr(Ⅵ)的最适条件;利用透射电镜(TEM)分析铬在细胞中的分布;利用傅里叶变换红外光谱研究细胞表面上参与Cr(Ⅵ)还原的官能团;利用紫外-可见(UV-Vis)分光光度法测定上清液、细胞表面和胞内可溶性组分中Cr(Ⅵ)和Cr(Ⅲ)的含量随时间的变化。结果球形红细菌还原Cr(Ⅵ)的最佳条件为光照厌氧、初始浓度100.0 mg/L、初始pH为7.0和培养温度30.0℃。TEM分析表明,球形红细菌胞内存在由Cr(Ⅵ)还原积累的Cr(Ⅲ)。菌体表面的-OH、-NH和-C=O等官能团参与了Cr(Ⅵ)的还原与Cr(Ⅲ)的积累。结论球形红细菌能有效还原Cr(Ⅵ),其机制包括生物还原和积累。

Objective To investigate the optimal conditions and related mechanisms for the biological reduction of high-toxic hexavalent chromium Cr(Ⅵ)into low-toxic trivalent chromium Cr(Ⅲ)by Rhodobacter sphaeroides. Methods The effect of different physical and chemical factors on the reduction of Cr(Ⅵ)by R. sphaeroides was tested to determine the optimal conditions for reducing Cr(Ⅵ). The distribution of chromium in the R. sphaeroides cells was analyzed by the transmission electron microscopy(TEM). The functional groups involved in the Cr(Ⅵ)reduction on the cell surface were investigated by the analysis of Fourier transform infrared spectra. The UV-Vis spectrophotometry was used to determine the change in Cr(Ⅵ)and Cr(Ⅲ)contents in the supernatant,cell surface and intracellular soluble fraction with times. Results The optimal conditions for Cr(Ⅵ)reduction involved the anaerobic cultivation with illumination,initial concentration of Cr(Ⅵ)100.0 mg/L,initial pH 7.0 and cultivating temperature 30.0℃. The TEM analysis revealed the existence of accumulated Cr(Ⅲ)by the reduction of Cr(Ⅵ)in the R. sphaeroides cells. The functional groups on the cell surface of R. sphaeroides,including the-OH,-NH and-C=O groups,participated in the reduction of Cr(Ⅵ)and accumulation of Cr(Ⅲ). Conclusion R. sphaeroides could effectively reduce Cr(Ⅵ),and the mechanism was likely to involve the biological reduction and accumulation.