Molecular approach for phytoremediation and phytomining of metal-contaminated sites

Abstract

Bioharvesting of metals from high biomass crops grown in soil substrates, particularly those associated with sub-economic mineralization is termed phytomining. It is a recent more advanced technology of phytoremediation to produce low volume, sulphide-free ‘bio-ore’, which can either be safely disposed of or, if the target metal is of sufficient economic value, smelted, and recovered. This technology has potential application in the mineral industry to return an economic profit by commercial production of metals via cropping. There are also enormous potential environmental benefits from these phenomena. Certain plant to extract metals from soil is commercially feasible. These specially selected plants—called hyperaccumulators—are known for their ability to take up and store particular metals. Recovery of metals from these plants can be defined as Phytoextraction. There are two basic applications: phytomining, where valuable naturally occurring elements are harvested and phytoremediation, where non-naturally occurring contaminants are recovered for secure disposal or reuse. Both are relatively new technologies and require fundamental research before becoming widely adopted by either the mining industry or environmental practitioners. These plants would be burned after harvest to create a biomass energy byproduct, with the respective metal recovered from the ash. In this way the land can then be converted to productive farming activities providing sustainability for the region and a natural method for these local people to transition their economy from mining to agriculture. Hyperaccumulators are good candidates in phytoremediation, particularly for the removal of heavy metals. Phytoremediation efficiency of plants can be substantially improved using genetic engineering technologies. Metal and metalloid contaminations seriously threaten the health of a large number of people worldwide and require novel, low-cost, flexible and effective phytoremediation technologies. The identification of unique genes from natural hyperaccumulators and their subsequent transfer to fast-growing species is a promising approach to enhance the phytoremediation abilities of plant species. Recent research results, including over expression of genes whose protein products are involved in metal uptake, transport, and sequestration, or act as enzymes involved in the degradation of hazardous organics, have opened up new possibilities in phytoremediation.