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Microbial Metalloproteins-Based Responses in the Development of Biosensors for the Monitoring of Metal Pollutants in the Environment
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Metalloproteins have a particular structure with sequential arrangement of amino acids promoting higher selectivity to specific metals compared to other metal-binding proteins. This attribute makes them very attractive as bioreceptors for biosensors (Fig. 1). Bontidean et al. (1998) developed sensors based on proteins (GST-SmtA and MerR) with distinct binding sites for heavy metal ions by overexpressing the above proteins in E. coli and immobilizing the pure proteins at surface of gold electrode. Following exposure to zinc, cadmium, copper, and mercury ions, the selectivity and sensitivity of the two protein-based biosensors were measured; the MerR-based electrodes showed an accentuated selectivity for mercury only, while the GST-SmtA electrodes were able to sense all the four heavy metals. Corbisier et al. (1999)overexpressed the fusion protein GST-SmtA, containing glutathione-S-transferase linked to the Synechococcal metallothionein protein in E. coli from an expression vector pGEX3X containing SmtA, the fusion protein was then immobilized on gold surface to prepare the biosensor.
Genetic Strategies for Strain Improvement
Published in Daphne L. Stoner, Biotechnology for the Treatment of Hazardous Waste, 2017
Polymers elaborated by microorganisms can take many forms. Factors controlling the structure of extracellular polysaccharides are not well understood, and these molecules are not readily altered using current genetic techniques. In other instances, such as secreted enzymes or peptides, alteration in polymer structure by genetic techniques is straightforward and well characterized. There are a number of metal binding proteins including ferritin, metallothionenes, heme proteins, and other proteinaceous metal chelators. Recent genetic engineering of a metal binding site in a protein has been reported47 providing opportunities for speculation regarding mutated or genetically engineered proteins being used to absorb heavy metals. In all but the most specialized cases, where extremely low final metal concentrations are required, proteins as heavy metal adsorbents will most likely not be commercially competitive with biologically or chemically synthesized polysaccharides or other adsorbents. Because of the relatively high molecular weight of even small proteins, a protein with many metal binding sites per molecule will still absorb less metal on a weight basis than a simple polysaccharide.
Environmental remediation using metals and inorganic and organic materials: a review
Published in Journal of Environmental Science and Health, Part C, 2022
Haragobinda Srichandan, Puneet Kumar Singh, Pankaj Kumar Parhi, Pratikhya Mohanty, Tapan Kumar Adhya, Ritesh Pattnaik, Snehasish Mishra, Pranab Kumar Hota
Tunable biopolymers could be prepared in line with tunable polymer to recover metal. In tunable biopolymer, one part is metal-binding protein and the other is a biopolymer with an active transition (tunable) phase. The metal-binding protein could be sourced from nature or genetically engineered and fused with a phase-tunable biopolymer. Also known as a nanobiomaterial, the resulting tunable biopolymer is effective in removing heavy metals. Elastin biopolymer (ELB) has shown phase transition in a range of conditions.75 A bacterial metal regulatory protein MerR was synthesized and fused with ELB to remove Hg. MerR poses a high binding affinity toward mercury (typically, 3–4-fold higher affinity than other heavy metals). Mercury binding was found to be in the ratio of 0.5 mercury/tunable biopolymer with limited binding of competing metals, viz., cadmium, nickel and zinc. Mercury was recovered by the TPT method wherein the tunable biopolymer was reusable.37 Multiple cycles ensured that mercury concentration reduced to as low as is acceptable in potable water. Tunable biopolymer having histidine-based metal-binding domain and showing phase transition activity was useful in Cd2+ recovery. The biopolymer network was resolubilised at <25 °C and remained functional even after several recovery cycles.38