Abstract
The target of the present study was to quantify the capacity of different commercially available yeast derivatives to bind E. coli F4 and Salmonella Typhimurium. In addition, a correlation analysis was performed for the obtained binding numbers and the mannan-, glucan- and protein contents of the products, respectively. In a subsequent experiment, different yeast strains were fermented and treated by autolysis or French press to obtain a concentrated yeast cell wall. The capacity of yeast cell wall products to bind E. coli F4 and Salmonella Typhimurium was assessed with a quantitative microbiological microplate-based assay by measuring the optical density (OD) as the growth parameter of adhering bacteria. Total mannan and glucan were determined by HPLC using an isocratic method and a Refractive Index (RI) Detector. Total protein was determined by Total Kjeldahl Nitrogen (TKN). Statistical analyses were performed with IBM SPSS V19 using Spearman correlation and Mann Whitney U Test.Different yeast derivatives show different binding numbers, which indicate differences in product quality.Interestingly, the binding numbers for Salmonella Typhimurium are consistently higher (between one and two orders of magnitude) than for E. coli F4.We could demonstrate some statistical significant correlations between the mannan- and glucan content of different yeast derivatives and pathogen binding numbers; however, for the different yeast strains fermented under standardized laboratory conditions, no statistically significant correlations between the mannan- and glucan content and the binding numbers for E. coli and Salmonella Typhimurium were found.Interestingly, we could demonstrate that the yeast autolysis had a statistically significant difference on E. coli binding in contrast to the French press treatment. Salmonella binding was independent of these two treatments.As such, we could not give a clear statement about the binding factors involved. We propose that many more factors apart from mannan- and glucan content, such as cell wall structure, strain diversity, structural diversity, structural surroundings, and non-specific interactions play important roles in pathogen immobilization.
Highlights
Yeast derivatives such as yeast cell wall products and recently yeast autolysate products are sold worldwide as feed supplements, some of which claim to bind enteropathogenic bacteria such as E. coli and Salmonella spp
Different commercially available yeast cell wall products and autolysate products were tested for their ability to bind E. coli F4 and Salmonella Typhimurium: E. coli F 4 binding numbers ranged between 101 and 103 CFU/mg yeast; Salmonella Typhimurium binding numbers between 103 and 104 CFU/mg yeast
There is much in the literature describing this adherence mechanism and mode(s) of action of yeast derivatives (Mourao et al 2006; Oyofo et al 1989; Sharon and Ofek 2000; Shoaf-Sweeney and Hutkins 2008; Snellings et al 1997; Spring et al 2000; Terre et al 2007; Yang et al 2008)
Summary
Yeast derivatives such as yeast cell wall products and recently yeast autolysate products are sold worldwide as feed supplements, some of which claim to bind enteropathogenic bacteria such as E. coli and Salmonella spp. Yeast cell wall products have been in the market for a long time, their binding capacity and the mechanism of pathogen binding is still not well understood. An important initial event in bacterial pathogenesis is the adherence of bacteria via their surface lectins to host intestinal cells. Infections are initiated only after the microorganism has first adhered to the host cell surface. If this initial adherence can be inhibited, so can the subsequent infection. This approach forms the basis of antiadherence strategies with the most studied being receptor-analogs, which include oligosaccharides (ShoafSweeney and Hutkins 2008)
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