Physicochemical characterization of extracel lular polymeric substances (eps) of bacillus atrophaeus and the potential use in heavy metal removal

QUIROGA AROMATARIS; ESCUDERO L.A; MASUELLI M.A; VILLEGAS L.B

san juan

Congreso; XLI Reunión Anual, Sociedad Biologica de Cuyo; 2023

universidad nacional de san juan

Extracellular polymeric substances (EPS) are microbial polysaccharide. In previous work was evaluated the EPS production by Bacillusatrophaeus in presence of glucose or saccharose, with or without Cu(II) or Cr(VI). The results showed that production was independent ofthe carbon source but increased significantly with the presence of metals. The objective of this work was to physicochemical characterize ofEPS produced by B. atrophaeus and to study its heavy metal removal capacity. EPS was produced in the absence or presence of Cu(II) orCr(VI). The EPS solutions were dried on a glass plate for 24 h, in order to obtain a powder structure to perform both structural and thermalstability analysis using Fourier transform infrared spectroscopy (FTIR), determination of the thermal stability of the material bythermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). Also, Scanning Electron Microscopy - Energy DispersiveX-ray spectroscopy (SEM-EDX) analysis was performed on the EPS produced under all work conditions. Finally, to evaluate the ability EPSbinding metals in aqueous systems, equilibrium dialysis experiments were carried out by placing dialysis tubing (14 kDa MWCO membrane)containing the EPS solution (67 mg/L of EPS) in closed glass flasks with 50 mL of the metal solution. The flasks were placed in an orbitalshaker (150 rpm) for 24 h. Residual heavy metal concentrations were analyzed using an atomic absorption spectrophotometer (AAS). Theresults of the analysis with SEM-EDX and heavy metal removal with the EPS determined that only Cu(II) was adhered by EPS. The FTIRanalysis demonstrated the presence of the functional groups –OH, -CH2, C=O, COO, C-O in all EPS. In EPS obtained in the Cu(II) andCr(VI) presence, the functional groups determined were C-O-C, 1,2,4 trisubstituted pyranosic ring and monosubstituted pyranosic ring. TheTGA characterization resulted in a decomposition temperature of 250ºC in all EPS. With the DSC characterization the transition temperaturewas 57ºC in the EPS obtained without the presence of metals, 71ºC in the presence of Cr(VI) and 66ºC in the presence of Cu(II). Nonepresented a melting point. The characteristics of EPS of B. atrophaeus suggest that, it can be used as a potential copper adsorbent inbioremediation process.