New mycotoxin adsorbents based on tri-octahedral bentonites for animal feed

In the present work different clays have been characterized according to their mycotoxins adsorbent ability. Firstly, 27 bentonite clays from different geographical origins were evaluated, at 0.02% w/v, using an in vitro screening method versus five mycotoxins (aflatoxin B-1, AFB1; deoxynivalenol, DON; ochratoxin A, OTA; fumonisin B-1, FB1; and, zearalenone, ZEN) by EnzymeLinked Immunosorbent Assay (ELISA). Subsequently, 7 bentonite clays (6 of which were trioctahedral bentonites) selected from the preliminary test, and 7 commercial adsorbent products were subjected to an in vitro equilibrium adsorption experiment (at 0.02% w/v) against six concentrations of AFB1 (0.02-4 mg/L), and OTA (0.05-1 mg/L) by using simulated gastrointestinal (GI) juices, and successively analysed by HPLC-FD. Equilibrium isotherm functions were fitted to the data by nonlinear regression analysis. In vitro adsorption equilibrium experiments showed that AFB1 adsorption was very high with all the adsorbents tested. In particular, the seven pre-selected bentonites adsorbed most of the AFB1 present at the lower level tested, while only three of these reached more than 50% of OTA adsorption. Adsorption increased inversely to the toxin concentration and both Langmuir and Freundlich isotherm models fitted well to the data. Generally, the pre-selected bentonites (B1-B7) showed better mycotoxin adsorption than commercial products (C1-C7) at all levels of mycotoxins tested. The 10-fold dose increase of the best tri-octahedral bentonite (B4) rendered a more effective adsorption of OTA, reaching almost 75% of adsorption (at pH 5).