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Genetic characterization of fructooligosaccharides metabolism by Lactobacillus paracasei 1195
Prebiotic oligosaccharides, such as fructooligosaccharides (FOS), are nondigestible food ingredients which influence the gastrointestinal tract (GI) microflora by selectively stimulating the growth and activity of certain probiotic and indigenous strains of Lactobacillus and Bifidobacterium. Despite considerable commercial and research interests on the prebiotic functionalities of FOS, the molecular mechanism by which FOS are metabolized by lactobacilli and bifidobacteria remains largely unexplored. The primary goal of this research, therefore, is to establish the genetic basis for FOS metabolism by Lactobacillus paracasei 1195, a strain that is capable of utilizing FOS as sole carbon source. Microarray-based gene expression analyses revealed that the FOS metabolic pathway is encoded by a putative operon constitutes of six genes, fosABCDXE, which encode proteins similar to components of a fructose/m an nose phosphotransferase system (PTS) and a cell wall-associated β-fructosidase. The cell surface localization of the β-fructosidase encoded by fosE suggested that these substrates are hydrolyzed extracellularly, followed by uptake of the hydrolysis products via the fructose/mannose-specific PTS. Functional analysis of the fos genes demonstrated that the fos operon is not only essential for the utilization of FOS, but also for other structurally-related fructose-containing sugars, such as oligofructose, inulin, levan, and sucrose. Expression of the fos genes was repressed in the presence of glucose. In addition, a typical diauxic growth pattern was observed when L. paracasei cells were grown in the presence of both FOS and glucose, which further indicated that FOS metabolism was subjected to catabolite regulation. Finally, cloning and expression of the fosE gene in a non-FOS-fermenting probiotic strain, L. rhamnosus GG, enabled the recombinant strain to metabolize FOS, oligofructose, inulin, levan, and sucrose. Results from this investigation have provided insights into how certain intestinal species of Lactobacillus metabolize FOS. Importantly, we have demonstrated the feasibility of developing probiotic strains with improved metabolism for FOS and other prebiotic oligosaccharides, which will likely increase the persistence of these probiotics and expand their functionality that contribute to the physiological health of their host. ^
Agriculture, Food Science and Technology|Biology, Microbiology|Chemistry, Biochemistry
Goh, Yong Jun, "Genetic characterization of fructooligosaccharides metabolism by Lactobacillus paracasei 1195" (2005). ETD collection for University of Nebraska - Lincoln. AAI3194114.