Galacto-oligosaccharides Derived from Lactulose Exert a Selective Stimulation on the Growth of Bifidobacterium animalis in the Large Intestine of Growing Rats M. Carmen Marín-Manzano, † Leticia Abecia, † Oswaldo Herna ́ ndez-Herna ́ ndez, ‡ M. Luz Sanz, ‡ Antonia Montilla, # Agustín Olano, # Luis A. Rubio, † F. Javier Moreno, # and Alfonso Clemente* ,† † Estació n Experimental del Zaidín (CSIC), Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain ‡ Instituto de Química Orga ́ nica General, Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain # Instituto de Investigaciones en Ciencias de la Alimentació n (CIAL, CSIC-UAM), Campus de Cantoblanco, Universidad Autó noma de Madrid, Spain ABSTRACT: There is increasing interest in identifying novel dietary nondigestible carbohydrates capable of modulating the composition and/or metabolic activities of the gut microbiota. This work assessed the differential modulatory influence of novel galacto-oligosaccharides derived from lactulose (GOS-Lu) in comparison with commercial galacto-oligosaccharides derived from lactose (GOS-La) in gut microbiota of growing rats (5 weeks old). Rats were fed either a control diet or diets containing 1% (w/ w) of GOS-Lu or GOS-La, and cecal and colonic contents were collected after 14 days of treatment. Compared to controls, GOS-Lu had significantly more bifidobacteria within the large intestine, showing a significant and selective increase of Bifidobacterium animalis in the cecum and colon; however, no significant differences in the number of bifidobacteria among GOS- Lu and GOS-La groups were observed. Both types of GOS significantly increased the number of the Eubacterium rectale/ Clostridium coccoides group. These findings support a prebiotic role of galactosyl-fructoses in functional foods. KEYWORDS: bifidobacteria, Bifidobacterium animalis, galacto-oligosaccharides, gut microbiota, lactulose, prebiotic ■ INTRODUCTION The human gastrointestinal tract contains an extraordinary number (10 trillion−100 trillion and more than 200 phylotypes) of resident commensal bacteria existing in homeostasis with the host. 1 This endogenous microbiota establishes a synbiotic mutualistic relationship and has a major impact upon the nutrition and health of the host, via the supply of nutrients, conversion of metabolites, control of epithelial cell proliferation/differentiation, pathogen exclusion, and stimulation of the immune system. 2 Given the emergent evidence of the key role played by the gut microbiota in health and disease, there is growing interest in identifying non- digestible functional food ingredients that are selectively fermented and allow specific changes in the composition and/or activity of the gut microbiota, which confers a beneficial effect on the host. 3 These dietary compounds, named prebiotics, favor the growth of beneficial bacteria and inhibit the growth of undesirable, potentially pathogenic bacteria, including Salmonella sp., Campylobacter jejuni, Helicobacter pylori, and Escherichia coli, among others. A growing number of studies support the conclusion that prebiotics could exert beneficial effects not only in the large intestine but also within the entire human body and/or contribute to the prevention/ remission of intestinal or systemic pathologies. 4,5 Ingestion of prebiotics typically increases the population of Bifidobacterium and Lactobacillus species, a widely accepted measure of prebiotic effect to date; in addition, a shift in the populations of other microorganisms, such as Eubacterium and Roseburia, has been reported to play a key role in butyrate synthesis, which is essential for the maintenance and protection of the normal colonic epithelium. The modulatory effect of prebiotics on gut microbiota has been associated with improvement in overall health, enhancement of defense mechanisms of the host to gut infections, accelerated recovery of gut disturbances, and better absorption of minerals. 6 Currently, the major prebiotic oligosaccharides on the market are inulin, fructo-oligosacchar- ides (FOS), and galacto-oligosaccharides (GOS). 7 The latter are nondigestible, at least partially, carbohydrates, which are usually composed by 2−10 molecules of galactose and 1 molecule of glucose, being primarily synthesized from lactose by the action of β-galactosidases of fungal, bacterial, or yeast origin, to result in lactose-derived GOS (GOS-La). The prebiotic properties of GOS-La in vitro have been reported consistently. 8−10 GOS-La have been demonstrated to increase the bifidobacterial population of fecal microbiota in healthy human volunteers; 11,12 however, such a positive effect was not observed in other related studies. 13,14 These dissimilarities can be attributed to a number of factors including the type, purity, and composition of the GOS used, as well as differences in the experimental design and methodological aspects. 15 Recently, the synthesis of lactulose-derived GOS (GOS-Lu) has attracted the attention of the scientific community due to their prospective prebiotic applications, being recognized mainly for their ability to promote the growth of bifidobacteria in human fecal slurries. 16,17 A detailed characterization of Received: May 22, 2013 Revised: July 15, 2013 Accepted: July 16, 2013 Published: July 16, 2013 Article pubs.acs.org/JAFC © 2013 American Chemical Society 7560 dx.doi.org/10.1021/jf402218z | J. Agric. Food Chem. 2013, 61, 7560−7567