Malik Anushree
Department of Applied Chemistry, Faculty of Engineering, Utsunomiya University, 7-1-2 Yoto,Utsunomiya, Tochigi 321-8585, Japan.
Environ Int. 2004 Apr;30(2):261-78. doi: 10.1016/j.envint.2003.08.001.
Heavy-metal pollution represents an important environmental problem due to the toxic effects of metals, and their accumulation throughout the food chain leads to serious ecological and health problems. Metal remediation through common physico-chemical techniques is expensive and unsuitable in case of voluminous effluents containing complexing organic matter and low metal contamination. Biotechnological approaches that are designed to cover such niches have, therefore, received great deal of attention in the recent years. Biosorption studies involving low-cost and often dead/pretreated biomass have dominated the literature and, subsequently, extensive reviews focusing on equilibrium and kinetics of metal biosorption have also come up. However, the low binding capacity of biomass for certain recalcitrant metals such as Ni and failure to effectively remove metals from real industrial effluents due to presence of organic or inorganic ligands limit this approach. At times, when pure biosorptive metal removal is not feasible, application of a judicious consortium of growing metal-resistant cells can ensure better removal through a combination of bioprecipitation, biosorption and continuous metabolic uptake of metals after physical adsorption. Such approach may lead to simultaneous removal of toxic metals, organic loads and other inorganic impurities, as well as allow optimization through development of resistant species. However, sensitivity of living cells to extremes of pH or high metal concentration and need to furnish metabolic energy are some of the major constraints of employing growing cells for bioremediation. The efforts to meet such challenges via isolation of metal-resistant bacterial/fungal strains and exploitation of organic wastes as carbon substrates have began. Recent studies show that the strains (bacteria, yeast and fungi) isolated from contaminated sites possess excellent capability of metal scavenging. Some bacterial strains possess high tolerance to various metals and may be potential candidates for their simultaneous removal from wastes. Evidently, the stage has already been set for the application of metal-resistant growing microbial cells for metal harvesting. This review focuses on the applicability of growing bacterial/fungal/algal cells for metal removal and the efforts directed towards cell/process development to make this option technically/economically viable for the comprehensive treatment of metal-rich effluents.
由于金属的毒性作用，重金属污染是一个重要的环境问题，并且它们在整个食物链中的积累会导致严重的生态和健康问题。通过常见物理化学技术进行金属修复成本高昂，且对于含有络合有机物和低金属污染的大量废水并不适用。因此，旨在填补此类空白的生物技术方法近年来受到了广泛关注。涉及低成本且通常为死体/预处理生物质的生物吸附研究在文献中占据主导地位，随后也出现了大量专注于金属生物吸附平衡和动力学的综述。然而，生物质对某些难处理金属（如镍）的低结合能力，以及由于有机或无机配体的存在而无法有效从实际工业废水中去除金属，限制了这种方法的应用。有时，当单纯的生物吸附去除金属不可行时，应用明智组合的生长型耐金属细胞可以通过生物沉淀、生物吸附以及物理吸附后金属的持续代谢摄取相结合的方式确保更好的去除效果。这种方法可能导致同时去除有毒金属、有机负荷和其他无机杂质，并且通过培育抗性物种实现优化。然而，活细胞对极端pH值或高金属浓度的敏感性以及需要提供代谢能量是利用生长细胞进行生物修复的一些主要限制因素。通过分离耐金属细菌/真菌菌株并利用有机废物作为碳源来应对这些挑战的努力已经开始。最近的研究表明，从污染场地分离出的菌株（细菌、酵母和真菌）具有出色的金属清除能力。一些细菌菌株对各种金属具有高耐受性，可能是同时从废物中去除金属的潜在候选者。显然，利用耐金属生长微生物细胞进行金属回收的应用阶段已经就绪。本综述重点关注生长型细菌/真菌/藻类细胞在金属去除方面的适用性，以及为使该方案在技术上/经济上可行以用于富金属废水的综合处理而在细胞/工艺开发方面所做的努力。
