Structure and function relationships of the binding of β- and ɑ-galactosylated oligosaccharides to K88 fimbriae of enterotoxigenic Escherichia coli

Chitosan-oligosaccharides (COS) are suitable acceptors for β-galactosidase, and galactosylated-COS prevent adhesion of enterotoxigenic Escherichia coli (ETEC) K88 to porcine erythrocytes. The structure and functional relationship of oligosaccharide binding to ETEC K88 fimbriae was investigated. β- or α-galacto-oligosaccharides (βGOS and αGOS), β-galactosylated melibiose, α-galactosylated lactose and β-/ɑ-galactosylated COS were produced with β-/α-galactosidase using lactose or melibiose as galactosyl donor. Oligosaccharides were fractionated with cation exchange and size exclusion chromatography; their ability to prevent pathogen adhesion was measured with a hemagglutination assay, ELISA with ETEC cells, or with purified K88 fimbriae. High molecular weight β-GalCOS, β-galactosylated melibiose, and βGOS had strong anti-adhesion activity. Other oligosaccharides had weak or no anti-adhesive effects against ETEC K88. The ability of oligosaccharides to prevent binding of ETEC K88 or purified K88 fimbriae decreased with decreasing molecular weight. An avenue for valorization of lactose from whey to produce oligosaccharides with specific biological activity is suggested.