Copper biosorption by Serratia plymuthica: crucial role of tightly bound extracellular polymeric substances in planktonic and biofilm systems

Heavy metals in aquatic environments pose significant environmental and human health risks, highlighting the urgent need for innovative remediation strategies. This study explores the role of bacterial extracellular polymeric substances as active binding surfaces for copper, in planktonic cells and biofilm-based adsorption systems. Serratia plymuthica strain As3-5a(5) achieved 92% Cu(II) biosorption (from an initial concentration of 3.14 mM) within 4 min in a non-proliferating planktonic cell system, and 98% biosorption in a biofilm-based system on sintered glass. Maximum metal biosorption was achieved by late stationary phase grown cells (72 h), likely due to an increased protein fraction in the tightly bound extracellular polymeric substances. When in the presence of real electroplating wastewater containing 40 mM Cu(II) at pH 1.9, planktonic cell system (10^11 cells mL−1) achieved 97% Cu(II) biosorption. These results highlight the strong potential of Serratia plymuthica strain As3-5a(5) for developing efficient biological systems for heavy metal removal from industrial wastewater. Furthermore, this work provides valuable insights into sustainable biotechnological approaches for copper remediation, with potential applications in catalytic processes and metal recovery within a circular economy framework. Future studies should involve synthetic biology approach to improve copper sequestration and to investigate the scalability of these systems to higher technology readiness levels under real industrial wastewater conditions.