Dietary fiber-driven shifts in mycobiota and short-chain fatty acid landscape in porcine hindgut.

This study employed a porcine model to investigate the dynamic effects of inulin (INU) and microcrystalline cellulose (MCC) on the profiles of intestinal short-chain fatty acids (SCFAs) and the composition of rectal fungal communities. Twenty-four healthy growing pigs were randomly allocated to three groups: a control group (CON), a 5% INU-supplemented group, and a 5% MCC-supplemented group. We hypothesized that soluble, rapidly fermentable INU and insoluble, slowly fermentable MCC would elicit distinct temporal dynamics in the fungal community, and that specific fungal taxa would correlate with SCFA profiles, reflecting a functional link between fungal succession and fiber fermentation. Gas chromatography analysis confirmed that dietary treatments induced distinct SCFA patterns in a time-dependent manner. On day 3, the concentrations of isobutyric acid (IBA) and isovaleric acid (IVA) were higher in the INU group than in the MCC group (P < 0.05). Conversely, on day 6, the concentrations of acetic acid (AA), propionic acid (PA), and total SCFA in the INU group were lower than those in both the CON and MCC groups (P < 0.05). ITS sequencing revealed that both INU and MCC markedly restructured rectal fungal communities, triggering temporal fluctuations in the relative abundances of Ascomycota and Basidiomycota, while selectively enriching functionally diverse genera. Specifically, the INU group exhibited enrichment of Vishniacozyma and Plectosphaerella at day 6, whereas the MCC group was characterized by elevated abundances of Trichosporon (day 6), Alternaria (day 10), Fusariella (day 10) and Paracremonium (day 10). Correlation analysis identified significant associations between key fungal genera and SCFA profiles. On day 3, the abundance of Aspergillus was negatively correlated with IVA and IBA concentrations. In line with this, pigs in INU group displayed reduced Aspergillus concomitant with increased IVA and IBA. On day 6, Vishniacozyma abundance was negatively associated with PA and total SCFAs, which agreed with the observation that the INU group had higher Vishniacozyma but lower PA to total SCFAs ratio relative to the CON and MCC groups (P < 0.05). Collectively, these findings highlight the functional involvement of intestinal fungi in dietary fiber degradation and offer novel insights into fungi-mediated dietary fiber digestion in the host gut.