Protein-based metal bio-cleaner for detoxification of wastewater

BACKGROUND Copper is an essential redox-active transition metal accessible in the very least amount in healthy living cells. Exposure to heavy metals through contaminated soil, the food chain and drinking of contaminated groundwater affects cellular metabolism in the human body. Hence, developing innovative next-generation approaches with a dual function such as efficient detection (sensor) and removal of heavy metals (Cu2+) in the environment is of paramount importance. Our study deals with an engineered biologically compatible green fluorescent protein (GFP) with metal-binding amino acid (3-aminotyrosine) for effective sensing and removal. RESULTS The fluorescent-based sensing of congener protein (amGFP) with heavy metal Cu2+ was extensively explored through fluorescence, circular dichroism spectroscopic and computational simulation approaches. The amGFP exhibits a low dissociation constant value of 5.25 mu mol L-1. In addition, the engineered congener protein was used as a bio-cleaner to remove Cu2+ from environmental samples. The copper binding capacity of engineered protein (amGFP, 346.46 mu g mL(-1)) showed a 1.6-fold increase compared with native protein (GFP, 214 mu g mL(-1)). GFP and amGFP immobilized on ethylenediamine-functionalized granular activated carbon (FGAC) were applied to environmental samples; FGAC-immobilized amGFP exhibited Cu2+ removal of about 85%, which was twofold higher than that of FGAC-immobilized GFP. CONCLUSIONS The results prove that amGFP was able to bind more copper than native GFP. This is an early attempt to develop a genetically encoded fluorescent protein that could be used to effectively remove Cu2+ from wastewater. (c) 2022 Society of Chemical Industry (SCI).