酿酒酵母与Ag^+的相互作用机制研究

Mechanism of Interaction Between Ag^+ and Saccharomyces cerevisiae

为探讨酿酒酵母与Ag+的相互作用机制,分析了酵母吸附Ag+过程中细胞阳离子的释放状况,并利用红外光谱(FTIR)、带能谱仪的扫描电镜(SEM-EDX)、带能谱仪的透射电镜(TEM-EDX)等手段表征了酵母细胞在吸附Ag+前后表面官能团的变化以及Ag+在酵母细胞中的存在位置和状态.结果表明,酵母细胞吸附Ag+伴随着大量细胞阳离子K+、Na+、Mg2+、Ca2+的释放.Ag+的存在会抑制体系pH值增加,并促进Mg2+、Ca2+的释放.与Ag+的吸附类似,K+、Na+、Mg2+、Ca2+的释放也很快,并且符合准二级动力学方程.酵母对Ag+的吸附,可被认为是离子交换机制和共价结合机制共同发挥作用.FTIR证明酵母表面羧基对Ag+的吸附发挥重要作用.电镜分析结果表明,酵母细胞表面不仅吸附了Ag+,同时产生更高浓度的含Ag沉淀物,使Ag+从溶液中去除,这些含Ag沉淀不均匀地分布于细胞表面,含Ag沉淀的性质以及形成过程还需要借助其他分析手段进行进一步确认.

To understand the characteristics of Ag^＋ biosorption by the waste biomass of Saccharomyces cerevisiae, the release phenomena of the cell physiological cations,such as K^＋ , Mg^2＋ , Ca^2＋ , Na^＋ , and pH value change during Ag^＋ uptake were investigated. The presence of Ag^＋ promoted the release of the cations,and decreased the absorption of H^＋ .Ion exchange was one of the mechanisms involved in metal-microbe interaction. Ag^＋ also exhibited a degree covalent binding with the biomass. Both Ag^＋ uptake and cation release （K^＋ , Mg^＋ , Ca^2＋ or Na^＋ ） followed the pseudo-second order kinetics. Fourier transform infrared spectroscopy （FTIR） indicated that the carboxyl group on the surface of the cells could play important role in metal-microbe interaction. The scanning electron microscopy with energy-dispersive X-ray analysis （SEM- EDX） and transmission electron microscopy with energy-dispersive X-ray analysis （TEM-EDX） were used to directly observe the change of the component elements and surface configuration of the cells before and after the interaction of the microbe with Ag ^＋ , and the results proved that Ag^＋ was adsorbed by the cell surface. Simultaneously,the precipitate containing Ag with higher concentration than the surface-adsorbed Ag was formed on the cell surface also resulted in the removal of Ag^＋ from the aqueous solution.