Kinetics and Efficiency of Copper and Zinc Biosorption by Enterobacter cloacae and Klebsiella grimontii in Association with Arthrocnemum macrostachyum from Lake Manzala

Abstract Heavy metal pollution poses serious environmental and health risks worldwide, with aquatic ecosystems like Lake Manzala being particularly vulnerable. Bioremediation using bacterial biosorbents offers a sustainable solution for heavy metal removal. Aim The present study aimed at exploring the copper and zinc biosorption potentials of some bacterial isolates recovered from the rhizosphere of Arthrocnemum macrostachyum prevailing in Lake Manzala environment. Methods A total of 6 bacterial isolates were screened for metal biosorption efficiency. The best metal biosorbent isolates were identified by 16S rRNA gene sequencing. Factors influencing metal uptake, including pH, initial metal concentration, biosorption kinetics, and biosorbent phase, were analyzed. Isotherm models, biosorption kinetics models, FTIR and TEM analyses were used to investigate the biosorption mechanisms. Results The highest biosorption efficiencies were 59.47% for Cu and 53.30% for Zn. The most effective Cu-biosorbent was identified as Enterobacter cloacae , while the Zn-biosorbent was Klebsiella grimontii . Optimal biosorption occurred at pH 5.5 for E. cloacae and pH 4.5 for K. grimontii, with maximum accumulation observed at 25 mg L⁻ 1 metal concentration, beyond which efficiency declined. No significant differences were observed between living and autoclaved cells, indicating that passive biosorption was the primary sufficient mechanism for both bacterial strains. TEM analysis confirmed intracellular metal accumulation and extracellular polysaccharide existence. Conclusions This study highlights the exceptional Cu and Zn removal efficiency of these bacterial strains, providing insights into microbial metal sorption mechanisms. These findings pave the way for the development of microbial-based bioremediation technologies to mitigate heavy metal pollution in aquatic ecosystems.