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

Abstract

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 °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 Δ G 0) and exothermic (negative Δ H 0). For EX16 and BETA, the favourable enthalpic contributions (negative Δ H 0 values) to OA binding, were associated to unfavourable entropic contributions (negative Δ S 0 values). By contrast, the entropic contribution to OA binding was favourable (positive Δ S 0 values) in the case of LEC. The calculated values of the heat capacity (ΔCp) were close to zero, indicating the absence of a temperature dependency for Δ H and Δ S. 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.