Nano-water hyacinth protein adsorbent as soil amendment alleviates cadmium stress in common bean seedlings by improving soil enzymes and mitigating oxidative stress

Heavy metal pollution is a serious environmental problem. Most of the current techniques used to mitigate the toxic effects of heavy metals have limitations. This creates an urgent need to explore safer and more efficient methods to address these toxic effects. This study investigates the potential of nano-water hyacinth protein (nano-WHP) as an adsorbent and soil amendment to mitigate cadmium pollution. Nano-WHP is derived from water hyacinth protein and immobilized on nano-chitosan. The Cd adsorption capacity and removal efficiency of nano-WHP were determined. Nano-WHP was applied as a soil amendment to examine its impact on soil enzyme activity and the growth of common bean plants under Cd stress. Nano-WHP could remove 96% of Cd with an adsorption capacity of 150 mg Cd g⁻¹. When used as a soil amendment under Cd stress, nano-WHP positively influenced soil enzyme activity, enhancing soil health and promoting the growth of common bean plants. The growth of nano-WHP-treated plants increased by approximately 35% and 50% in the first and second stages, respectively, compared to the control group under cadmium stress. Furthermore, nano-WHP significantly reduced oxidative stress markers such as lipid peroxidation, DNA oxidation, protein oxidation, and H₂O₂ levels, with reductions of about 90.63%, 85.13%, 79.35%, and 81.85%, respectively, compared to untreated plants. This reduction in oxidative stress markers is attributed to the lower availability of Cd and the heightened activity of the antioxidant machinery in nano-WHP-treated plants. These results establish a foundation for the formulation of sustainable and economically feasible methodologies to mitigate Cd contamination.