School of Environmental Science and Engineering of Guangdong University of Technology, Guangzhou, Guangdong 510006, China.
School of Environmental Science and Engineering of Guangdong University of Technology, Guangzhou, Guangdong 510006, China.
J Hazard Mater. 2024 Aug 5;474:134760. doi: 10.1016/j.jhazmat.2024.134760. Epub 2024 May 29.
In this study, we investigated the adsorption of Cd(II) and the biosynthesis of CdS quantum dots (QDs) mediated by cells of sulfate-reducing bacteria before and after the removal of EPS to determine whether EPS or the cell wall plays a major role. Potentiometric titration revealed that the concentration of proton-active binding sites on cells with EPS (EPS-intact) was notably higher than that on cells without EPS (EPS-free) and that the sites were predominantly carboxyl, phosphoryl, hydroxyl, and amine groups. The protein content in EPS-intact cells was higher, and thus the Cd(II) adsorption capacity was stronger. The CdS QDs biosynthesized using EPS-intact possessed better properties, including uniform size distribution, good crystallinity, small particle size, high fluorescence, and strong antimicrobial activity, and the yields were significantly higher than those of EPS-free by a factor of about 1.5-3.7. Further studies revealed that alkaline amino acids in EPS play a major role and serve as templates in the biosynthesis of QDs, whereas they were rarely detected in the cell wall. This study emphasizes the important role of EPS in the bacterial binding of metals and efficient recycling of hazardous waste in water.
在这项研究中，我们调查了硫酸盐还原菌细胞在去除 EPS 前后对 Cd(II)的吸附和 CdS 量子点（QDs）的生物合成，以确定 EPS 或细胞壁在其中起着主要作用。电位滴定表明，具有 EPS（完整 EPS）的细胞上质子活性结合位点的浓度明显高于没有 EPS（无 EPS）的细胞，并且这些位点主要是羧基、磷酸基、羟基和胺基。完整 EPS 细胞中的蛋白质含量较高，因此 Cd(II)的吸附能力更强。使用完整 EPS 合成的 CdS QDs 具有更好的性能，包括均匀的粒径分布、良好的结晶度、较小的粒径、高荧光和强抗菌活性，产量比无 EPS 细胞高约 1.5-3.7 倍。进一步的研究表明，EPS 中的碱性氨基酸在 QDs 的生物合成中起主要作用，并作为模板，而在细胞壁中很少检测到它们。这项研究强调了 EPS 在细菌结合金属和有效回收水中有害废物方面的重要作用。
