Heavy metals (HM) in water bodies pose serious environmental and health threats. Bacterial exopolymeric substances (EPS) can be employed as active surfaces for HM cation binding. Biofilm-based systems, consisting of microporous microcarriers inoculated with specific metal-resistant bacterial strains, can represent an operative implementation of planktonic ones. This study investigates copper (Cu(II)) removal from electroplating wastewaters by Serratia plymuthica strain As3-5a(5) characterized for Cu(II) high resistance (MIC of 476 mg L-1), EPS production (90 mg g-1 d.w) and biofilm formation (2.24 OD595nm/OD600nm). In non-proliferating cell planktonic system, strain As3-5a(5) removed up to 40% of Cu(II) from a 200 mg L−1 solution and 30% from wastewater. Metal desorption achieved by 0.1 M nitric acid was in the order of 50%. In biofilm-based systems, strain As3-5a(5) exhibited Cu(II) removal of 43% on cellulose acetate filter, 45% on calcium alginate beads, and 83% on gardening substrate, in 4-minute contact time. To enhance cell viability, optimize cellular structure, and increase EPS formation, molasses was added as growth substrate. Preliminary data evidenced that EPS production increased, while maintaining the prevalent monosaccharides mannose and rhamnose as determined by NMR analysis. Flow cytometry method, assessed by using a Concanavalin-A fluorescent lectin with specific binding to the strain monosaccharides, will further validate these data. This work provides insights for the development of a sustainable biological method for metal removal, also in view of new utilization of metal-bacterial complexes for catalytic purposes or recovery of metal itself in a circular economy frame. Acknowledgement. Research supported by Fondazione CARIPLO-Circular Economy 2020 project num. 1069-2020 “Heavy Metal Bio-recovery and Valorization-HMBV” https://sites.unimi.it/hmbv/. Melzi A. is awarded of a PhD fellowship by the University of Milan - Food Systems PhD Program.
Microporous microcarrier biofilm for copper removal from industrial wastewaters / A. Melzi, M. Colombo, C. Valli, L. Cavalca. ((Intervento presentato al 7. convegno International Symposium on Biosorption and Biodegradation/Bioremediation – BioBio : 16-20 june tenutosi a Praga nel 2024.
Microporous microcarrier biofilm for copper removal from industrial wastewaters
A. Melzi;M. Colombo;C. Valli;L. Cavalca
2024
Abstract
Heavy metals (HM) in water bodies pose serious environmental and health threats. Bacterial exopolymeric substances (EPS) can be employed as active surfaces for HM cation binding. Biofilm-based systems, consisting of microporous microcarriers inoculated with specific metal-resistant bacterial strains, can represent an operative implementation of planktonic ones. This study investigates copper (Cu(II)) removal from electroplating wastewaters by Serratia plymuthica strain As3-5a(5) characterized for Cu(II) high resistance (MIC of 476 mg L-1), EPS production (90 mg g-1 d.w) and biofilm formation (2.24 OD595nm/OD600nm). In non-proliferating cell planktonic system, strain As3-5a(5) removed up to 40% of Cu(II) from a 200 mg L−1 solution and 30% from wastewater. Metal desorption achieved by 0.1 M nitric acid was in the order of 50%. In biofilm-based systems, strain As3-5a(5) exhibited Cu(II) removal of 43% on cellulose acetate filter, 45% on calcium alginate beads, and 83% on gardening substrate, in 4-minute contact time. To enhance cell viability, optimize cellular structure, and increase EPS formation, molasses was added as growth substrate. Preliminary data evidenced that EPS production increased, while maintaining the prevalent monosaccharides mannose and rhamnose as determined by NMR analysis. Flow cytometry method, assessed by using a Concanavalin-A fluorescent lectin with specific binding to the strain monosaccharides, will further validate these data. This work provides insights for the development of a sustainable biological method for metal removal, also in view of new utilization of metal-bacterial complexes for catalytic purposes or recovery of metal itself in a circular economy frame. Acknowledgement. Research supported by Fondazione CARIPLO-Circular Economy 2020 project num. 1069-2020 “Heavy Metal Bio-recovery and Valorization-HMBV” https://sites.unimi.it/hmbv/. Melzi A. is awarded of a PhD fellowship by the University of Milan - Food Systems PhD Program.
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