Erythromycin was produced by Saccharopolyspora erythraea in batch mode. Selective adsorption was the method chosen to enable the recovery of erythromycin from growth media. The following sorbents were used: neutral resins (XAD-4, XAD-7 and XAD-16) and ion-exchange resins, Amberlite(TM) IRA-410 (anionic resin) and Amberlite(TM) IR-120 (cationic resin). A mathematical kinetic model for the adsorption of erythromycin, from fermentation media, versus time, on these resins was used. The maximum erythromycin adsorption from fermentation media, at 303 K, was attained with XAD-16 (0.38 mmol/g),IR-120 (0.35 mmol/g) and XAD-7 (0.28 mmol/g) resins and a removal higher than 70% (m/v) was achieved with low sorbent loads (less than 1%, m/v). In addition, XAD-7 resin showed a better performance when it was considered the adsorption per unit of surface area (1.22 x 10(-3) mmol/m(2)). For every solute/sorbent system tested, adsorption equilibrium was attained in less than 3 b contact. The adsorption data for the sorbents XAD-16 and IRA-120 resins are correlated with Freundlich and Langmuir models. The thermodynamic parameters such as Delta H-ads, Delta S-ads and Delta G(ads) were calculated to predict the nature of adsorption. The positive value of enthalpy (6 kJ/mol) suggest that the original salt in the resin is bound strongly, while the positive value of entropy (54 J/mol K) means that liberation of the salt into the solution is entropically favorable, and the favorable entropy drives the overall process, with a free energy of adsorption of -10 kJ/mol. (C) 2005 Elsevier B.V. All rights reserved.
