Pectic oligosaccharide structure-function relationships: Prebiotics, inhibitors of Escherichia coli O157:H7 adhesion and reduction of Shiga toxin cytotoxicity in HT29 cells

• Published in: Food chemistry 2017-07, Vol.227, p.245-254
• Main Authors: Di, Rong, Vakkalanka, Malathi S., Onumpai, Chatchaya, Chau, Hoa K., White, Andre, Rastall, Robert A., Yam, Kit, Hotchkiss, Arland T.
• Format: Article
• Language: English
• Subjects: Anti-adhesion; Bacterial Adhesion; Escherichia coli Infections - microbiology; Escherichia coli O157 - genetics; Escherichia coli O157 - physiology; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Feces - microbiology; HT29 Cells; Humans; Oligosaccharides - chemistry; Oligosaccharides - metabolism; Orange pectic oligosaccharides; Pectins - chemistry; Pectins - metabolism; Prebiotics - analysis; rRNA depurination; Shiga Toxin - metabolism; Shiga Toxin - toxicity; Shiga toxin 2; STEC; TaqMan RT-qPCR
• ISSN: 0308-8146; 1873-7072
• DOI: 10.1016/j.foodchem.2017.01.100

•Determined bifidogenic citrus pectic oligosaccharide (POS) structural diversity.•Five citrus POS were anti-adhesive for Stx-producing E. coli O157:H7.•Developed a novel TaqMan-based RT-qPCR assay to measure rRNA depurination by Stx2.•Citrus POS samples reduced the cytotoxicity of Stx2 holotoxin in HT29 cells. Shiga toxin (Stx)-producing, food-contaminating Escherichia coli (STEC) is a major health concern. Plant-derived pectin and pectic-oligosaccharides (POS) have been considered as prebiotics and for the protection of humans from Stx. Of five structurally different citrus pectic samples, POS1, POS2 and modified citrus pectin 1 (MCP1) were bifidogenic with similar fermentabilities in human faecal cultures and arabinose-rich POS2 had the greatest prebiotic potential. Pectic oligosaccharides also enhanced lactobacilli growth during mixed batch faecal fermentation. We demonstrated that all pectic substrates were anti-adhesive for E. coli O157:H7 binding to human HT29 cells. Lower molecular weight and deesterification enhanced the anti-adhesive activity. We showed that all pectic samples reduced Stx2 cytotoxicity in HT29 cells, as measured by the reduction of human rRNA depurination detected by our novel TaqMan-based RT-qPCR assay, with POS1 performing the best. POS1 competes with Stx2 binding to the Gb3 receptor based on ELISA results, underlining the POS anti-STEC properties.