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Oligosaccharides, compounds that are composed of 2-10 monosaccharide residues, are major carbohydrate sources in habitats populated by lactobacilli. Moreover, oligosaccharide metabolism is essential for ecological fitness of lactobacilli. Disaccharide metabolism by lactobacilli is well understood; however, few data on the metabolism of higher oligosaccharides are available. Research on the ecology of intestinal microbiota as well as the commercial application of prebiotics has shifted the interest from (digestible) disaccharides to (indigestible) higher oligosaccharides. This review provides an overview on oligosaccharide metabolism in lactobacilli. Emphasis is placed on maltodextrins, isomalto-oligosaccharides, fructo-oligosaccharides, galacto-oligosaccharides, and raffinose-family oligosaccharides. Starch is also considered. Metabolism is discussed on the basis of metabolic studies related to oligosaccharide metabolism, information on the cellular location and substrate specificity of carbohydrate transport systems, glycosyl hydrolases and phosphorylases, and the presence of metabolic genes in genomes of 38 strains of lactobacilli. Metabolic pathways for disaccharide metabolism often also enable the metabolism of tri- and tetrasaccharides. However, with the exception of amylase and levansucrase, metabolic enzymes for oligosaccharide conversion are intracellular and oligosaccharide metabolism is limited by transport. This general restriction to intracellular glycosyl hydrolases differentiates lactobacilli from other bacteria that adapted to intestinal habitats, particularly Bifidobacterium spp.

A pseudo steady-state model for the kinetically controlled synthesis of galacto-oligosaccharides (GOS) with Aspergillus oryzae β-galactosidase is presented. The model accounts for the dynamics of lactose consumption and production of galactose, glucose, di, tri, tetra, and penta-oligosaccharides during the synthesis, being able to describe the total GOS content in the reaction medium at the experimental conditions evaluated. Experimental results show that the formation of GOS containing only galactose residues is significant at high conversions of substrate, which was taken into account in the model. The formation of enzyme transition complexes was considered and reasonable assumptions were made to reduce the number of parameters to be determined. The model developed has 8 parameters; 2 of them were experimentally determined and the other 6 were estimated by fitting to the experimental data using multiresponse regression. Temperature effect on kinetic and affinity constants was determined in the range from 40 to 55°C, and the data were fitted to Arrhenius type equation. Parameters of the proposed model are independent from the enzyme load in the reaction medium and, differently from previously reported models, they have a clear biochemical meaning. The magnitude of the kinetic and affinity constants of the enzyme suggests that the liberation of galactose from the galactosyl-enzyme complex is a very slow reaction and such complex is driven into GOS formation. It also suggests that the affinity for sugars of the galactosyl-enzyme complex is higher than that of the free enzyme., (Copyright © 2011 Wiley Periodicals, Inc.)

We investigated the effect of a mixture of long-chain fructo-oligosaccharides, galacto-oligosaccharides and acidic oligosaccharides on the number and consistency of stools and on immune system biomarkers in 104 supplemented and non-supplemented subjects (aged 9-24 months) with acute diarrhea. Interleukin-1 (IL-1), IL-1RA, IL-6, IL-8, IL-10, TNF-α and sIL-2R cytokine levels were determined. The significant decrease in number of stools and increase in stool consistency in the supplemented group was of little clinical relevance. The only significant change in pro- and anti-inflammatory cytokines was decreased TNF-α levels in the supplemented group. Prebiotic supplementation during acute diarrhea episodes did not influence the clinical course.