Structure and microbial-modulating evaluation of a sulfhydryl-modified pectin

In this study, we synthesized a modified form of pectin know as sulfhydryl group (-SH) modified pectin (PSH) by linking cysteine's amino groups and pectin's carboxyl group through amide bonds. The -SH amounts varied from 517 μmol/g to 732 μmol/g. Pectin (PEC) modified with -SH groups showed no significant alteration in chain structure, monosaccharide composition and molecular weight. Compared to PEC, PSH had a stronger interaction with mucus, and the strength of this interaction increased with the -SH amounts. In vitro fermentation indicated that PSH was fermentable by human fecal microbiota, and the -SH modified can prolong the overall fermentation time of PEC from 48 h to 72 h, as evidenced by the variations in pH values, total sugar, molecular weight, monosaccharide consumption and short-chain fatty acids production. Furthermore, microbial analysis revealed that PSH significantly increased the abundance of Faecalibacterium and Bifidobacterium while decreasing the abundance of Klebsiella and Collinsella. These results provided a solid foundation for the potential use of -SH modified PEC as a mucoadhesive material for delivering active substances and regulating the effect of PEC on gut microbiota.