Yeast cell based feed additives: studies on aflatoxin B1 and zearalenone

Thirty commercially available yeast cell wall products and two reference bentonites were tested for their ability to bind aflatoxin B-1 (AFB1) and zearalenone (ZON) in buffer solutions at pH 3 and pH 6.5 as well as in real gastric juice. For most products, the binding efficacy of AFB1 correlated with the ash content, which was between 2.6 and 89%, and constituted the inorganic non-volatile components, such as mineral clays, of the samples. Samples with smectite as the main ash component showed the highest binding efficacy; yet, a correlation with the content of mannanooligosaccharides (MOS) and beta-glucans from yeast cell walls was not observed. Products containing >30% ash showed AFB1 adsorption values >90% at least in one of the investigated media whereas most products with <10% ash did not exceed adsorption rates of 20%. In the case of ZON, adsorption efficiency ranged between 10 and 60%. It tended to be lowest for products with MOS and beta-glucan contents <10% and greatest for products with MOS and beta-glucan contents >50%. However, there was no general correlation between the adsorption of ZON and the concentration of MOS and beta-glucans. Different products of one brand sold in different countries were observed to bind AFB1 to different degrees, which was explained by the difference in ash contents and mineral composition. In the case of ZON, differences in adsorption between products of the same brand were less pronounced.