Exploring Metal Interactions with Released Polysaccharides from Cyanothece sp. CE4: A chemical and Spectroscopic Study on Biosorption Mechanism

This study investigates the potential of released polysaccharides (RPS) from the halophilic cyanobacterium Cyanothece sp. CE4 as biosorbents for heavy metals, specifically copper (Cu), nickel (Ni), and zinc (Zn). The RPS-containing supernatant was collected and evaluated for metal uptake using ICP-OES, SEM-EDX, FT-IR spectroscopy and XAS analysis. Results revealed a strong binding affinity for Cu, followed by Ni and Zn, with RPS functional groups (e.g., hydroxyl and carbonyl) playing a key role in metal coordination. The RPS efficiently removed metals from both monometallic and multimetallic solutions, highlighting their adaptability in competitive environments. XAS analysis showed metal-specific coordination environments, with Ni preferring O bonds, Zn favoring Cl, and Cu binding to both. The halophilic nature of Cyanothece sp. CE4 likely enhances its metal interaction capabilities. Remarkably, extracted RPS removed up to 67 mg Cu per gram of RPS dry weight, surpassing previously reported values. These findings enhance the understanding of the potential of RPS-containing supernatants in metal bioremediation and offer insights for optimizing such processes. Furthermore, they emphasize the dual functionality of Cyanothece sp. CE4 as a sustainable biosorbent resource and a valuable contributor to circular resource management.