Influence of pH on Complexing of Model β-D-Glucans with Zearalenone
Abstract:Previous studies have shown that isolated β-(1,3 and 1,6)-D-glucans and related alkali-extracted fractions from the cell wall of Saccharomyces cerevisiae are able to complex with zearalenone in vitro (affinity up to 50%) and thus may reduce the bioavailability of toxins in the digestive tract. The complexation mechanisms involve cooperative interaction between the two chemical entities that can be computed by Hill's model. Various linear or branched soluble or insoluble β-D-glucans were evaluated to elucidate their roles in the adsorption mechanisms under three pH conditions (3.0, 6.0, and 8.0) found in the digestive tract. A constant quantity of each β-D-glucans (1 mg/ml) was mixed at 39°C with increasing amounts of zearalenone (2 to 100 μg/ml), and the amount of bound toxin was measured. Acidic and neutral conditions gave the highest affinity rates (64 to 77%) by β -(1,3)-D-glucans, whereas alkaline conditions decreased adsorption except when β-(1,6)-D-glucan side chains were branched on β-(1,3)-D-glucans. Alkaline conditions appear to impede the active three dimensional conformation of β-D-glucans and favor single helix and/or random coil structures. Study of the equilibrium between β-D-glucan–bound and free toxins revealed that two types of chemical interactions occur during toxin complexation with β-D-glucans, identified as weak chemical linkages such as hydrogen and van der Waals bonds.
Document Type: Research Article
Affiliations: 1: UR1213 Institut National de la Recherche Agronomique, Unité de Recherches sur les Herbivores, Centre de Clermont-Theix, 63122 St-Genès Champanelle and Alltech-France, 2-4 avenue du 6 Juin 1944, 95190 Goussainville, France 2: UMR-CNRS 5504, UR-INRA 792, Institut National des Sciences Appliquées, 135 avenue de Rangueil, 31077 Toulouse Cedex 4, France 3: Laboratoire de Génie Chimique et Biologique, CUST, Université Blaise Pascal—Clermont-Ferrand II, 24 avenue des Landais, 63174 Aubière Cedex, France 4: UMR-CNRS 6504, Laboratoire de Synthèse et E ´ tude des Systèmes à Inteêret Biologique, Université Blaise Pascal—Clermont-Ferrand II, 63177 Aubière Cedex, France 5: Alltech-France, 2-4 avenue du 6 Juin 1944, 95190 Goussainville, France 6: UR1213 Institut National de la Recherche Agronomique, Unité de Recherches sur les Herbivores, Centre de Clermont-Theix, 63122 St-Genès Champanelle, France
Publication date: 2004-12-01
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