Effect of temperature on in vitro ochratoxin A biosorption onto yeast cell wall derivatives

In vitro biosorption of ochratoxin A (OA) onto three yeast industry products: a vinasse containing yeast cell walls (EX16), a purified yeast beta glucan (BETA) and a yeast cell wall fraction (LEC), has been studied as a function of the temperature. Equilibrium binding assays were performed from 4 to 37 degrees C. The best models for OA biosorption onto EX16, BETA and LEC were identified as respectively Hill's, Freundlich and Brunauer-Emmett-Teller models. LEC was the most effective adsorbent for OA removal in aqueous solutions. All biosorption processes were spontaneous (negative AGO) and exothermic (negative Aff). For EX16 and BETA, the favourable enthalpic contributions (negative AHO values) to OA binding, were associated to unfavourable entropic contributions (negative ASO values). By contrast, the entropic contribution to OA binding was favourable (positive ASO values) in the case of LEC. The calculated values of the heat capacity (ACp) were close to zero, indicating the absence of a temperature dependency for AH and AS. The results suggest that the remarkable OA biosorption onto LEC involves both polar and non-polar non-covalent interactions and the concomitant reorganization of the water molecules of the solvent. (c) 2005 Elsevier Ltd. All rights reserved.