Characterization of Pseudomonas veronii 2E Extracellular Polymeric Substances as Cd(II) Ligand for Metal Removal

M. L. FERREIRA; A. CASABUONO; A. COUTO; S. A. RAMIREZ; D. L. VULLO

Boston

Congreso; ASM Microbe 2016; 2016

American Society for microbiology

Biological treatments are innovative technologies available for industrial wastewaters containingmetals. Some bacteria are adapted to metal polluted environments as consequence of thedevelopment of survival strategies or just by secretion of extracellular polymeric substances(EPS). EPS are microbial products excreted (soluble) or associated to the cell surface and arecomposed by a complex mixture of proteins, polysaccharides, nucleic acids, lipids and otherpolymeric compounds. They can protect cells from metal toxicity due to the presence of differentfunctional groups available as ligands. The aim of this study was to evaluate the complexingcapacity of the major component in EPS produced by the indigenous strain P.veronii 2E forpotential application in wastewater treatment. EPS were produced by growing cells at 32 ºC in aminimal medium M9-2% (v/v) glycerol, precipitated from culture supernatants with ethanol andpurified by both dialysis (MW>12,400Da) and enzymatic treatments (DNase I and Proteinase K).After treating this last fraction (EPSenz) with sodium deoxycholate, two major fractions wereobtained: lipopolysaccharide LPS and extracellular polysaccharide ExP, both in similarproportions. FT-IR spectroscopy was performed to study the functional groups present in LPSand ExP that may interact with Cd(II). The ability of EPS, EPSenz, LPS and ExP to complexCd(II) was determined by an electrochemically monitored titration (ASV) at pH 7.5 (25±1°C).One family of moderate strength binding sites was observed in all fractions with a log K´(conditional formation constant) of 5.5, while the ligand concentration (μmoles of binding sites/gdry weight) was 65 μmol/g EPS, 500 μmol/g EPSenz, 278 μmol/g LPS and 16 μmol/g ExP. LPSis the purified fraction with great affinity for the complexation of the cation, consistent with thehigh biosorptive capacity of the whole cells observed in previous studies. The simple productionand purification of the soluble EPS is a promissory alternative as a metal retaining agent tominimize hazardous discharges of industrial wastes and to open the possibility of metal recovery..