Abstract
Prebiotic oligosaccharides have the ability to generate important changes in the gut microbiota composition that may confer health benefits to the host. Reducing the impurities in prebiotic mixtures could expand their applications in food industries and improve their selectivity and prebiotic effect on the potential beneficial bacteria such as bifidobacteria and lactobacilli. This study aimed to determine the in vitro potential fermentation properties of a 65 % galacto-oligosaccharide (GOS) content Bimuno® GOS (B-GOS) on gut microbiota composition and their metabolites. Fermentation of 65 % B-GOS was compared with 52 % B-GOS in pH- and volume-controlled dose-response anaerobic batch culture experiments. In total, three different doses (1, 0·5 and 0·33 g equivalent to 0·1, 0·05 and 0·033 g/l) were tested. Changes in the gut microbiota during a time course were identified by fluorescence in situ hybridisation, whereas small molecular weight metabolomics profiles and SCFA were determined by 1H-NMR analysis and GC, respectively. The 65 % B-GOS showed positive modulation of the microbiota composition during the first 8 h of fermentation with all doses. Administration of the specific doses of B-GOS induced a significant increase in acetate as the major SCFA synthesised compared with propionate and butyrate concentrations, but there were no significant differences between substrates. The 65 % B-GOS in syrup format seems to have, in all the analysis, an efficient prebiotic effect. However, the applicability of such changes remains to be shown in an in vivo trial.
Highlights
In vitro and in vivo studies involving prebiotic oligosaccharides have been carried out using inulin and its fructooligosaccharide (FOS) derivatives, as well as various galactooligosaccharides (GOS)
The method for Bimuno® GOS (B-GOS) purification has been studied by Goulas et al[6] in order to reduce the amount of free glucose and galactose produced during its synthesis, and it led to the removal of 92 % of glucose by fermentation with Saccharomyces cerevisiae
Our results showed acetate as the dominant SCFA produced for both substrates with significant differences between 4 and 8 h of fermentation using 65 % B-GOS at 0·033 g/l (P < 0·01) (Table 3)
Summary
In vitro and in vivo studies involving prebiotic oligosaccharides have been carried out using inulin and its fructooligosaccharide (FOS) derivatives, as well as various galactooligosaccharides (GOS). GOS can be defined as a mixture of the end products of lactose breakdown by β-galactosidases, containing two to eight saccharide units, with a terminal glucose unit[2] These mixtures can be complex and their structures are often imperfectly characterised. The structural and functional relationship of GOS plays a role in targeting the Bifidobacterium genus[3] Another important aspect is the presence of impurities such as monosaccharaides, disaccharides or metabolic products from purification steps. Removing these compounds can lead to a mixture with a GOS content as high as possible that can be better used to study fermentation and structural properties of novel prebiotics in in vitro experiments. This study aimed to determine the potential prebiotic activity of a purified 65 % GOS content B-GOS, compared with 52 % GOS content B-GOS, used as positive control in in vitro dose–response batch cultures
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