ix, 201 pages : illustrations (some color) ; 23 cm
주기사항
Adviser: Maria L. Marco Thesis (Ph.D.)-- University of California, Davis, Food Science and Technology, 2014 Includes bibliographical references
관련전자자료: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:3685251 요약: Probiotics are defined as living microorganisms which when administrated in adequate amounts confer a health benefit on the host. Although dairy products are the primary food carriers of probiotics to the gastrointestinal tract to promote human health, the effects of milk and other dairy foods on functional traits expressed by probiotics in the intestine are largely unknown. Thus, this dissertation aims to begin to identify the probiotic -- milk matrix interactions that result in improvements to human health. Specifically, we investigated strains of Lactobacillus casei, species commonly associated with milk and fermented dairy products either as adjunct cultures or probiotics. In this dissertation, the contributions of milk to the health-benefiting performance of probiotic L. casei were investigated in healthy and colitic mice. We found that incubation of L. casei BL23 in milk at 4°C improved the intestinal persistence of this probiotic strain compared with other incubation methods and delivery matrices (Chapter 2). Using gel-free proteomics, we identified the proteomes of L. casei in milk and constructed L. casei mutants deficient in expression of milk-inducible proteins DltD (D-alanine transfer protein), FabH (3-oxoacyl-[acyl-carrier-protein] synthase III), RecA (recombinase A), or Sod (superoxide dismutase). These mutants were impaired in competitive fitness in the mouse intestine. To show the milk-mediated beneficial effects of probiotics in the digestive tract, wild-type and the dltD and recA knockout mutants of L. casei were tested in a dextran sulfate sodium (DSS) - induced colitis murine model (Chapter 3). Protection against colitis was measured using a disease activity index which took weight loss, histology scores, and stool composition into account. L. casei BL23 protected against the development of DSS - induced colitis when ingested in milk but not in a nutrient-free buffer. Consuming the milk alone also provided some protective effects. However, L. casei dltD and recA mutants, unlike wild-type cells, did not protect against DSS colitis. Feeding milk or L. casei altered the colonic immune responses and cecal microbiota compared with DSS-treated mouse controls but did not result in maintaining an immune and microbiota profiles found in healthy animals. Lastly, the proteomes of L. casei strain ATCC334 and BL23 expressed during incubation at 4 °C in milk and standard laboratory media (MRS) and at 37 °C in MRS (control) were identified and compared to show conserved responses of different strains of L. casei during exposure to refrigeration and milk (Chapter 4). Proteins involved in translation and ribosomal structure and biogenesis were highly enriched in both strains incubated at 4 °C. Incubation in milk resulted in increased levels of proteins involved in amino acid transport and metabolism, proteins associated with modifying the cell membrane and extracellular composition as well as oxidative stress. The findings of this dissertation indicate that dairy based formulations and storage conditions improve the health-benefiting performance of probiotics in the mammalian gut. This information is important for understanding the molecular mechanisms responsible for probiotic-host interactions in the gut.