Xylo-oligosaccharides and lactitol promote the growth of Bifidobacterium lactis and Lactobacillus species in pure cultures

The current screening study aimed at identifying promising prebiotic and synbiotic candidates. The fermentation of xylo-oligosaccharides, xylan, galacto-oligosaccharide, fructo-oligosaccharide, polydextrose, lactitol, gentiobiose and pullulan was investigated in vitro. The ability of these established and potential prebiotic candidates to function as a sole carbon source for probiotic (Bifidobacterium and Lactobacillus), intestinal and potential pathogenic microbes (Eubacterium, Bacteroides, Clostridium, Escherichia coli, Salmonella, and Staphylococcus) was assessed in pure cultures. Xylo-oligosaccharides were fermented with high specificity by the tested Bifidobacterium lactis strains and lactitol by lactobacilli, whereas galacto-oligosaccharides, fructo-oligosaccharides and gentiobiose were utilised by a larger group of microbes. Xylan, polydextrose and pullulan were utilised to a limited extent by only a few of the tested microbes. The results of this screening study indicate that xylo-oligosaccharides and lactitol support the growth of a limited number of beneficial microbes in pure cultures. Such a high degree of specificity has not been previously reported for established prebiotics. Based on these results, the most promising prebiotics and synbiotic combinations can be selected for further testing.

Xylo-oligosaccharides enhance the growth of bifidobacteria and Bifidobacterium lactis in a simulated colon model

A semi-continuous, anaerobic colon simulator, with four vessels mimicking the conditions of the human large intestine, was used to study the fermentation of xylo-oligosaccharides (XOS). Three XOS compounds and a xylan preparation were fermented for 48 hours by human colonic microbes. Fructo-oligosaccharides (FOS) were used as a prebiotic reference. As a result of the fermentation, the numbers of Bifidobacterium increased in all XOS and xylan simulations when compared to the growth observed in the baseline simulations, and increased levels of Bifidobacterium lactis were measured with the two XOS compounds that had larger distribution of the degree of polymerisation. Fermentation of XOS and xylan increased the microbial production of short chain fatty acids in the simulator vessels; especially the amounts of butyrate and acetate were increased. XOS was more efficient than FOS in increasing the numbers of B. lactis in the colonic model, whereas FOS increased the Bifidobacterium longum numbers more. The selective fermentation of XOS by B. lactis has been demonstrated in pure culture studies, and these results further indicate that the combination of B. lactis and XOS would form a successful, selective synbiotic combination.