Adsorption of Zearalenone by β-d-Glucans in the Saccharomyces cerevisiae Cell Wall

Abstract

Cell walls of yeasts and bacteria are able to complex with mycotoxins and limit their bioavailability in the digestive tract when these yeasts and bacteria are given as feed additives to animals. To identify the component(s) of the yeast cell wall and the chemical interaction(s) involved in complex formation with zearalenone, four strains of Saccharomyces cerevisiae differing in their cell wall glucan and mannan content were tested. Laboratory strains wt292, fks1, and mnn9 were compared with industrial S. cerevisiae strain sc1026. The complex-forming capacity of the yeast cell walls was determined in vitro by modelling the plots of amount of toxin bound versus amount of toxin added using Hill's model. A cooperative relationship between toxin and adsorbent was shown, and a correlation between the amount of beta-D-glucans in cell walls and complex-forming efficacy was revealed (R2 = 0.889). Cell walls of strains wt292 and mnn9, which have higher levels of beta-D-glucans, were able to complex larger amounts of zearalenone, with higher association constants and higher affinity rates than those of the fks1 and sc1026 strains. The high chitin content in strains mnn9 and fks1 increased the alkali insolubility of beta-D-glucans from isolated cell walls and decreased the flexibility of these cell walls, which restricted access of zearalenone to the chemical sites of the beta-D-glucans involved in complex formation. The strains with high chitin content thus had a lower complex-forming capacity than expected based on their beta-D-glucans content. Cooperativity and the three-dimensional structure of beta-D-glucans indicate that weak noncovalent bonds are involved in the complex-forming mechanisms associated with zearalenone. The chemical interactions between beta-D-glucans and zearalenone are therefore more of an adsorption type than a binding type.

Ability ofLactobacillus rhamnosusGAF01 to remove AFM1in vitroand to counteract AFM1immunotoxicityin vivo

“…It was suggested that carbohydrate-rich mannoproteins or glucans might be involved in the binding, as levels of complex formation appear to be strain-and toxin-specific (Shetty and Jespersen, 2006). Raju and Devegowda (2000) attributed the binding of aflatoxins by yeast cell walls to mannan oligosaccharides, while zearalenone binding was attributed to glucan components (Yiannikouris et al, 2004). Haskard et al (2001) suggested that AFB 1 binds predominantly to carbohydrate and protein components of viable cells.…”

Yeast cell based feed additives: studies on aflatoxin B1and zearalenone

“…The mechanism of binding by β-Dglucans has been investigated by Yiannikouris and co-workers and has been discussed in several publications, e.g. (Yiannikouris et al 2004a;Yiannikouris et al 2006;Yiannikouris et al 2004b;Yiannikouris et al 2004c). It was shown that it is important to differentiate between the adsorption affinity of whole yeast cell wall and processed cell wall.…”

Reduction of Ochratoxin A Levels in White Wine by Yeast Treatments

“…The cell wall polysaccharides (glucan and mannan), proteins and lipids have been reported to exhibit numerous different adsorption mechanisms, e.g., hydrogen bonding, ionic or hydrophobic interaction 11 . Similarly, it has been observed that the β-D glucans isolated from S. cerevisiae cell wall is directly involved in the binding process of zearalenone 21 .…”