Prebiotic potential of fructo-oligosaccharides produced by aspergillus ibericus in a bacterial community representative of the gut microbiota

Abstract

Introduction The positive effects of prebiotics on human health are associated to their capacity to modulate gut microbiota and consequently, regulate the production of metabolites, such as the short-chain fatty acids (SCFA). Herein, the prebiotic potential of microbial-fructo-oligosaccharides (microbial-FOS) produced by a co-culture of Aspergillus ibericus and Saccharomyces cerevisiae YIL162W [1] was evaluated in a designed bacterial consortium representing the healthy human gut microbiota.

Methodology The prebiotic effect of the microbial-FOS was compared with two non-microbial commercial inulin-type samples: Raftilose®P95 and Frutalose®OFP. The bacterial consortium was composed by Bacteroides dorei, Bacteroides vulgatus, Bifidobacterium adolescentis, Bifidobacterium longum, Escherichia coli, Lactobacillus acidophilus, and Lactobacillus rhamnosus at a similar phyla proportion as found in the human colon. Fermentations were run for 30 h in FEED media [2]. During fermentation, the pH, bacterial growth (monitored by optical density measurement and selective media inoculation), SCFA production and sugar consumption (assessed by HPLC) were evaluated.

Results and Discussion Bacterial growth decreased in the following order: glucose > microbial-FOS > Raftilose® P95 > Frutalose® OFP. Microbial-FOS stimulated a higher Bifidobacterium and Lactobacillus probiotic strains growth, as compared with other samples. The E. coli growth was suppressed at the beginning of fermentation, probably due to a pH reduction caused by lactate produced by Lactobacillus. Lactate and SCFA (such as acetate, propionate, and butyrate) were produced using all samples. The microbial-FOS sample (initial concentration: 20 g/L) produced the highest amount of lactate (12.2±0.1 g/L) and SCFA (4.0±0.1 g/L). The bacterial consortium seems to consume preferentially microbial-FOS presenting higher degree of polymerization (consumption: 60.8±0.1 % GF4 (1- fructofuranosyl nystose); 57.2±0.1 % GF3 (nystose); 49.6±0.1 % GF2 (kestose)).

Conclusions Microbial-FOS were successfully used as a substrate by a microbiota bacterial consortium. Also, microbial-FOS stimulated higher Bifidobacterium and Lactobacillus growth as well as higher total SCFA and lactate concentrations among the other substrates studied. The prebiotic potential of microbial-FOS produced by A. ibericus was demonstrated, providing a promising indication of its usability as a food ingredient with strong prebiotic features.