Alkali Extraction of beta-D-Glucans from Saccharomyces cerevisiae Cell Wall and Study of Their Adsorptive Properties toward Zearalenone

摘要

The isolated cell wall of Saccharomyces cerevisiae has some capacity to adsorb zearalenone (affinity near 30%) and reduce the bioavailability of toxins in the digestive tract.The adsorption process was quantified in vitro,and the data obtained when plotted with Hill's equation indicated a cooperative process.The model showed that the adsorption capacity was related to the yeast cell wall composition.This work focused on the role of various beta-D-glucan types in the efficacy of zearalenone adsorption by yeast cell wall and sought to elucidate some of the adsorption mechanisms.Zearalenone was mixed at 37degC with a constant quantity of alkali-soluble or alkali-insoluble beta-D-glucans isolated from yeast cell walls,and the amount of adsorbed zearalenone was measured.Given that the alkali solubility of beta-D-glucans is a determining factor for their three-dimensional conformation and that the alkali-insoluble fraction had a greater affinity (up to 50%) than the alkali-soluble fraction (approx16%),it was concluded that the three-dimensional structure strongly influences the adsorption process.The alkali insolubility of beta-D-glucans led to the formation of single and/or triple helices,which have been identified as the most favorable structures for zearalenone adsorption efficacy.The beta(1,3)-D-glucan and beta-(1,6)-D-glucan compositions of the two alkali-extracted fractions and their involvement in the adsorption process are discussed.