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 °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 ΔG0) and exothermic (negative ΔH0). For EX16 and BETA, the favourable enthalpic contributions (negative ΔH0 values) to OA binding, were associated to unfavourable entropic contributions (negative ΔS0 values). By contrast, the entropic contribution to OA binding was favourable (positive ΔS0 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 ΔH and ΔS. 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.