Fabrication of smart chitosan composite beads for alleviate boron toxicity in a model plant (Lemna gibba): Characterization, toxicity assessment, and boron removal

Excessive boron (B) in aquatic ecosystems poses a significant threat to environmental health and biodiversity. In this respect, an attractive strategy should be evaluated to reduce B toxicity in the water environment and protect aquatic organisms. The study aims to reduce B-induced toxicity in a model plant, Lemna gibba, using smart chitosan-magnetic composite beads enriched with keratin, and further enhanced with boron-tolerant bacteria (Acinetobacter sp.). We tested different chitosan-magnetic composite beads for their B adsorption capacity, focusing on a specific type enriched with keratin for the first time in the literature. The effects of adding chitosan-magnetic composite beads in a test solution containing B mine effluent to alleviate B toxicity on L. gibba's growth parameters (frond number, biomass production, and EC50 value) were detailly evaluated in the experiment period. Accordingly, the chitosan-magnetic composite beads with keratin (Mag-Ch-K) demonstrated high B adsorption, with a maximum loading capacity of 2.875 mg/g at pH 7. The relative growth rate of L. gibba in a reactor containing Mag-Ch-K beads was measured to be approximately 2-fold (0.2065) higher than that of the control reactor (0.1212) without composite beads at 64 mg L−1 B concentration. More importantly, Mag-Ch-K bead significantly increased the plant's tolerance against B in the reactor matrix, as indicated by an EC50 value of 44.18 mg L−1 compared to 17.17 mg L−1 in the control. This study provides a promising approach to mitigate B toxicity in water bodies, offering a practical operation, high growth production, and preventing B pollution shock via modified bead with Acinetobacter sp. High B removal (76 %) was also achieved from reactors containing Mag-Ch-K-D through the high B-loading capacities and plant uptake. These dual benefits encourage designers to design chitosan and duckweed-based treatment systems for ecological conservation and pollution management in B-rich waters, such as B mine effluent pollution.