Colonic In Vitro Model Assessment of the Prebiotic Potential of Bread Fortified with Polyphenols Rich Olive Fiber

Abstract

The use of olive pomace could represent an innovative and low-cost strategy to formulate healthier and value-added foods, and bakery products are good candidates for enrichment. In this work, we explored the prebiotic potential of bread enriched with Polyphenol Rich Fiber (PRF), a defatted olive pomace byproduct previously studied in the European Project H2020 EcoProlive. To this aim, after in vitro digestion, the PRF-enriched bread, its standard control, and fructo-oligosaccharides (FOS) underwent distal colonic fermentation using the in vitro colon model MICODE (multi-unit colon gut model). Sampling was done prior, over and after 24 h of fermentation, then metabolomic analysis by Solid Phase Micro Extraction Gas Chromatography Mass Spectrometry (SPME GCMS), 16S-rDNA genomic sequencing of colonic microbiota by MiSeq, and absolute quantification of main bacterial species by qPCR were performed. The results indicated that PRF-enriched bread generated positive effects on the host gut model: (i) surge in eubiosis; (ii) increased abundance of beneficial bacterial groups, such as Bifidobacteriaceae and Lactobacillales; (iii) production of certain bioactive metabolites, such as low organic fatty acids; (iv) reduction in detrimental compounds, such as skatole. Our study not only evidenced the prebiotic role of PRF-enriched bread, thereby paving the road for further use of olive by-products, but also highlighted the potential of the in vitro gut model MICODE in the critical evaluation of functionality of food prototypes as modulators of the gut microbiota.

Multiunit In Vitro Colon Model for the Evaluation of Prebiotic Potential of a Fiber Plus D-Limonene Food Supplement

“…Batch cultures were run under these controlled conditions for a period of 26.26 h, during which samples were collected at 4 time points. Sampling was performed with a dedicated double syringe filtered system (Applikon Biotechnology) connected to a float drawing from the bottom of the vessels without perturbing or interacting with the bioreactor's ecosystem [20]. To guarantee a close control, monitoring and recording of fermentation parameters, the software Lucullus 3.1 (PIMS, Applikon Biotechnology) was used.…”

“…To address specific correlations among bacteria and molecules (preVOCs), two independent datasets were merged and computed by Spearman Rank analysis and visualized with a two-way joining heatmap, including Pearson dendrograms with complete linkage. The baselines of values (BL) for the volatilome and the core microbiota were obtained from the fecal slurry diluted in PBS, and the BM with the 1% (w/v) of substrates (FLS and FOS) after adaptation in the bioreactors and was expressed as the mean of three samples [20]. Normalization of datasets was performed with the mean centering method.…”

“…In this work, to study the potential prebiotic effect of FLS, we adopted MICODE, an in vitro gut model of the distal colon, to mimic the effect of human colon fermentation. MICODE was previously introduced [20], describing several quality controls related to microbiota and the volatilome used to validate the stability of the system. MICODE is able to maintain the original diversity, rarity, and richness of the human colon microbiota from the stool donation over the fermentation period, including upholding some Archea and more than 400 different OTUs [20].…”

“…MICODE was previously introduced [20], describing several quality controls related to microbiota and the volatilome used to validate the stability of the system. MICODE is able to maintain the original diversity, rarity, and richness of the human colon microbiota from the stool donation over the fermentation period, including upholding some Archea and more than 400 different OTUs [20]. In line with the latest definition of prebiotics [21], the use of an in vitro colon model sets the basis to study the prebiotic potential of foods while, at the same time, assessing the principal bacterial taxa and the volatilome [13].…”

“…In line with the latest definition of prebiotics [21], the use of an in vitro colon model sets the basis to study the prebiotic potential of foods while, at the same time, assessing the principal bacterial taxa and the volatilome [13]. The study of the volatilome generated during colonic fermentation of fiber is another fundamental aspect to study the prebiotic potential of a particular food or fiber because it can describe hundreds of compounds, including those derived from microbial metabolism (organic acids), and those transformed by the microbiota (bioactives) [20,21]. In particular, in the present work, the most important bacterial taxa and their metabolites were studied by a qPCR and SPME-GC-MS, respectively.…”