Changes in gut microbiota in predigested Hibiscus sabdariffa L calyces and Agave (Agave tequilana weber) fructans assessed in a dynamic in vitro model (TIM-2) of the human colon

Abstract

Hibiscus sabdariffa (Hb) calyces are a source of dietary fiber (DF) and phenolic compounds. Agave fructans (AF) and oligofructans (OF) are considered as soluble DF. The aim of the study was to investigate changes in gut microbiota upon feeding predigested Hb, AF, OF or Mix (Hb/AF) to a dynamic, validated in vitro model of the human colon (TIM-2), using sequencing of the V3-V4 regions of the 16S rRNA gene. A pooled human fecal microbiota was used. Production of short-chain fatty acids (SCFAs), branched-chain fatty acids (BSCFAs) and ammonia was also assessed. Samples were taken after 0, 24, 48 and 72 h. Principal component (PC) analysis of fermentation metabolites and relative abundance of genera was carried out, and extracted factors were based on eigenvalues >1.0 and explained >60% of variance. Fermentation of samples resulted in different SCFAS concentrations. The highest butyric acid production was on AF and OF, while the molar ratio of SCFAS on Hb was 63:18:18 for acetic, propionic and butyric acid, respectively. BSCFAS were also produced upon feeding the studied substrates, but in much lower concentrations. About 45 bacteria genera were identified and 10 of these were the most abundant changing during the fermentation time, amongst which a high relative abundance in Bifidobacterium, Bacteroides and Catenibacterium, that changed during the fermentation time depending of substrate. Hb feeding after 48 h led to Bifidobacterium being the most abundant genus. Two PCs were identified: after 24 h of fermentation PC1 was highly influenced by Bifidobacterium and Prevotella, which was related with Hb and SIEM feeding. Evaluation of the changes in metabolites and gut microbiota composition during colonic fermentation in a validated in vitro model provides a complete and reliable view of the potential prebiotic effect of different dietary fibers.