枯草芽孢杆菌对铀的富集及机理研究

为了研究枯草芽孢杆菌在培养条件下对铀的富集能力及机理,为该菌在铀污染治理中的应用提供理论基础。通过探究铀的初始浓度、培养时间、接种量各因素对枯草芽孢杆菌富集铀特性的影响,并且利用红外光谱(FTIR)、扫描电镜(SEM)、能谱(EDS)、X射线光电子能谱(XPS)和探究菌体富集铀的部位以探讨菌体富集铀的机理。结果表明,当接菌量为6%,培养时间为48 h时,枯草芽孢杆菌对UO_2~(2+)的富集达到平衡。UO_2~(2+)初始浓度为25~100 mg/L时,枯草芽孢杆菌可正常生长,并且对铀具有富集能力。枯草芽孢杆菌对铀的主要富集部位为细胞壁,约占菌体总吸附量的89%。SEM、EDS表明菌体与铀作用后,细胞表面粗糙,铀沉积在细胞表面及周围。FTIR图谱中出现了UO_2~(2+)的特征吸收峰,羟基、胺基、羧基及菌体蛋白质等活性位点参与枯草芽孢杆菌对铀的富集作用。XPS表明菌体吸附的铀多以U(VI)形式存在。说明在一定浓度范围内,枯草芽孢杆菌在培养条件下对铀有良好的富集效果。

Biosorption of Uranium by Bacillus subtilis and Its Mechanism

The thesis aims to study the enrichment capacity of uranium by Bacillus subtilis and its mechanism under culture conditions, and thus to provide a basis for the application of this bacterium in uranium pollution control. The effects of initial concentration of uranium, culture time, and inoculation amount on biosorption ability of Bacillus subtilis to uranium were discussed. The mechanism of uranium biosorption by Bacillus subtilis was discussed by FTIR, SEM, EDS, XPS as well as by studying uranium-enriched sites. The results showed that when the inoculation amount was 6%, culture time was 48 h, the biosorption could reach a balance level. When the initial concentration of UO22 was 25-100 mg/L, Bacillus subtilis could grow normally, and enriched the uranium. The cell wall was the main uranium enrichment site of Bacillus subtilis, accounting for about 89% of the total bacterial adsorption amount. SEM and EDS showed that the cell surface of Bacillus subtilis was rough, and uranium deposited on the surface and surrounding areas of Bacillus subtilis. FTIR spectra had showed the characteristic absorption peak of UO22 . And hydroxyl, amine, carboxyl and other active sites of bacterial protein took part in biosorption of Bacillus subtilis to uranium. XPS showed that U (VI) was the main form of uranium adsorbed by Bacillus subtilis. It indicated that in a certain concentration range, Bacillus subtilis had effective enrichment effect on uranium under culture conditions.