Degree

Doctor of Nutrition and Food Sciences (PNFS)

Department

School of Nutrition and Food Sciences

Document Type

Dissertation

Abstract

Fruit and vegetable production in Ghana were estimated at 371,811 tons in 2017 with tomatoes ranked among the top four most cultivated vegetables. The majority of the production goes to waste due to spoilage and lack of processing. Probiotics have recently gained much attention owing to claims about their potential health benefits. However, the inability of certain probiotics to survive gastric conditions remain a potential setback. Tomatoes can be processed into value added products including those fortified with probiotics. Such value-added products can be used as protectant for the delivery of probiotics to improve gut health. The objective of this study was to investigate the in vitro and in vivo (mouse model) efficacy of probiotic bacteria Lactobacillus casei and Lactobacillus rhamnosus for reducing colitis. The normally discarded tomato pomace obtained during tomato juice extraction which has fiber content of 24% was also investigated as a protectant for the probiotic bacteria.

For the in vitrotest, the viability of probiotics Lactobacillus rhamnosus (LG) and Lactobacillus casei (LC) in tomato juice was tested under simulated gastric and intestinal conditions. LG and LC survived the simulated gastric and intestinal conditions with viable cell counts above 6 log CFU/mL. In addition, tomato pomace, a normally discarded by-product from tomato juice processing was tested as a protectant for the probiotics. An improvement in viability of LC and LG was achieved and this was attributed to the fiber content. A growth kinetics study showed probiotics varied in growth behavior during fermentation, with bacteriocins and lactic acid as major metabolites. The bacteriocins were tested against Listeria innocua and at least 2 log CFU/g reduction in Listeria innocua cells was obtained. Two log reduction in Escherichia coliO15:H7 (EC) cells was obtained when it was incubated together with LC or LG.

In the in vivo study, C57BL/6 mice infected with Citrobacter rodentium to induce colitis were treated with the probiotics (LG or LC).It was realized from the in vivo study that probiotics influenced production of short chain fatty acids (acetate, butyrate and propionate).Probiotic activity also influenced gut inflammatory markers (IL-10, IL-12 and TNF-alpha). Histological evaluation of mouse colonic tissues showed probiotics reduced inflammation and damage to the colonic tissues. A study of the impact of the probiotics on the microbiota showed high prevalence of Bacteroidetes and Firmicutes compared to other phyla such as Proteobacteria, Actinobacteria, and Verrucomicrobia for all the test groups. Variations in the level of microbes such as Lactobacillus, Lactococcus, Eubacterium, and Citrobacter were attributed to the modulatory effect of the probiotics on the mouse microbiota. In summary, tomato juice and pomace could serve as a delivery system for probiotics. Probiotics may modulate the gastrointestinal microbiota and immune response to help relieve complications of intestinal inflammation (colitis) or diarrhea.

Date

7-1-2019

Committee Chair

Sathivel, Subramaniam

Available for download on Monday, June 22, 2026

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