A “heavy metal sponge” for selective removal and recovery of toxic or precious metals from water (844.8)

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Metallothionein (MT) is a low molecular weight metal binding protein. It has the unique ability to selective bind trace amounts of toxic heavy metals such as lead and cadmium. It does not bind essential metals such as sodium or calcium. We are developing a novel patented “heavy metal sponge” technology for the removal and recovery of toxic, e.g., lead and mercury, and precious metal, e.g., gold and platinum, from water. MT also has the ability to bind the lanthanides lanthanum and europium. Recombinant MT was cloned into pET vectors with and without a Pel secretory sequence, pPMpel, and pCODAmt, respectively. The protein is expressed in bacteria and purified to near homogeneity from cell lysates by a simple and cost effective method using FPLC anion exchange chromatography. The purity of the preparation was confirmed by SDS‐PAGE. Expression of MT and secretion of the protein using the pPMpel construct is pH dependent. The level of expression from both constructs was the same for IPTG ranging from 0.5 to 2.0 mM. The purified MT was used to determine the potential for removing trace amounts of heavy metal from seawater. The protein was mixed with seawater containing 100 ppt (trillion) of 109Cd. The protein/metal complex was then collected using a membrane filter centrifugal device and the flow through assayed for radioactivity. The efficiency of metal removal was determined from the radioactivity in the flow through. Under these conditions, 88% of the metal was removed from the seawater after a single centrifugation.Grant Funding Source: Funded by a grant from CSUPERB