酿酒酵母吸附重金属离子的研究进展

Review on Biosorption of Heavy Metal by Saccharomyces cerevisiae

重金属污染成为当今最重要的环境问题之一。生物吸附法是处理大体积低浓度重金属废水的一种理想方法,近年来有关的研究报道不断增多,但尚未实现工业化应用。酿酒酵母(Saccharomyces cerevisiae)不仅是具有实用潜力的生物吸附剂,也是研究重金属生物吸附机理的良好材料。结合自己的研究成果,总结了酿酒酵母作为生物吸附材料的优点、研究中的表现形式和吸附性能,重点讨论了酿酒酵母生物吸附机理,介绍了等温吸附平衡模型和动力学模型在酵母生物吸附中的应用情况。最后提出生物吸附进一步的研究方向。

Biosorption , Heavy metal pollution has become one of the most serious environmental problems today. regarded as a cost-effective biotechnology for treating heavy metal of low concentration in wastewater, has not been utilized at large scale successfully. It＇ s helpful to increase the knowledge of biosorption mechanism and decreasing the costs of biosorbents for the biosorption application. The yeast of Saccharomyces cerevisiae is an ideal biomaterial to be used for exploring the mechanism and for actual utilization because of its unique characteristics in spite of its relatively mediocre capacity of metal uptake to other fungi. The yeast can grow easily in cheap media, and is widely used in food and beverage manufacture. It＇ s also a safe by-product in large quantity as a waste of the fermentation industry, and easily manipulated at molecular level. The metal uptake specifically by S. cerevisiae was addressed. Firstly, it was discussed to use dead or live ceils in biosorption. The yeast can absorb toxic heavy metals （ Pb, Hg, Cd, etc）, precious metals （ Au, Ag, Pd, etc） and radionuclides （U, Am, etc）. Secondry, metal-binding capacity of various heavy metals by S. cerevisiae in different conditions were compared. Lead and uranium, for instances, can be effectively removed from dilute solutions, while copper is not easily removed. Thirdly, various mechanism of metal uptake by S. cerevisiae were summarized in details according to the position in which metals are located. Metal uptake process is influenced by the ratio of the initial concentration of metal ions and the concentration of biomass. Cellular wall and its components are important for metal uptake. Functional groups for metallic ion fixation have been identified. Uptake is typically accompanied by ion exchange and complexation, sometimes with precipitation （for Pb） and redox （for Au or Ag）. Intracellularly accumulated metal is associated with the cell membrane, vacuole and GSH, but may also be bound to other cellular organelles and biomolecules. The equilibrium and kinetic models used in the metal-yeast biosorption systems were also introduced. In most cases, classic Langrniur model and Freundlich model, widely used to describe single metal biosorption system of equilibrium, fit the experimental data very well. Pseudo-second order equation is often employed to describe biosorption process by S. cerevisiae. Finally, futher researches in metal biosorpiton by S. cerevisiae were proposed.