Fruit pulp (mango) and soluble fibre (pectin) impact bacterial diversity and abundance differently within the porcine large intestine

We examined the effects of a fruit cell wall matrix (mango pulp) and a soluble dietary fibre (pectin) on the porcine large intestinal (LI) bacterial community (caecum, proximal, mid- and distal colon). Pigs were fed one of three diets varying in carbohydrate content: wheat starch only (control-C), or two diets where some starch was substituted by 15% mango pulp(M) or 10% pectin(P). Metabolite end-product analyses were conducted. Bacterial community profiles were analysed through pyrosequencing of the 16S rRNA gene. End-product analyses (except propionic acid), revealed significant differences between the three diets, as well as between the four LI sites (P<0.001). C samples had the lowest short-chain fatty acid (SCFA) concentrations. Distally, SCFA values decreased over all diets, while differences between diets were reduced. Proximally, M and P samples had lower ammonia compared with C (P<0.001). The more molecularly-complex M diet was associated with increased bacterial diversity within Cae and PC, compared with C and P groups. For M samples, assigned 16S sequences were most associated with the phylum Bacteroidetes. Within groups, unique species (>1% sequence abundance) were: Bifidobacterium pseudolongum (C), Faecalibacterium prausnitzii (P), and Lactobacillus mucosae (M). Both forms of fruit fibre led to increased LI bacterial diversity proximally, promoting increased production of beneficial metabolites. Distally, these effects had diminished, which suggests that while these fibres are potentially beneficial to human health proximally, the addition of other, more slowly fermentable carbohydrates, may encourage carbohydrate fermentation along the entire tract.