Potential of cheddar cheese to impact on the gut microbiota

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Leeuwendaal, Natasha Kim
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University College Cork
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There is growing evidence in the scientific literature relating to the potential of food to programme gut microbiota and, in so doing, impact positively on gut-health. Fermented foods and in particular cheese, support a rich microbial population and are a well-recognized source of indigenous lacticaseibacilli, referred to as Non-Starter Lactic Acid Bacteria (NSLAB) that grow to high numbers in the cheese during ripening. Species such as Lacticaseibacillus paracasei and Lacticaseibacillus rhamnosus are common members of the NSLAB microbiota and are also recognised as an important component of a healthy gut microbiome. Indeed, many of the commercially successful probiotic bacteria include these species. Fermented foods are also highly nutritious and offer the potential to influence directly the growth of the indigenous gut microbiota. The hypothesis tested in this project was that cheese, along with its natural NSLAB populations, has the potential to positively affect the gut microbiota and thus be considered a food with added human health benefits. To explore this hypothesis, the potential of NSLAB to survive gastric transit was investigated by exposing the bacterial populations separated from the cheese matrix to Simulated Stomach and Duodenum Passage (SSDP) followed by plating on MRS medium. Populations of NSLAB, up to 107 CFU/g of cheese were recovered following this treatment suggesting that significant populations may survive gastric transit and thus, gain entry to the small and large intestine. A selection of 240 isolates surviving SSDP were characterised including examination for a number of typical probiotic characteristics. Arising from this, two strains, Lacticaseibacillus paracasei DPC 7150 and Lacticaseibacillus rhamnosus DPC 7102, were selected that demonstrated probiotic potential. To further investigate how these strains survive in cheese and to explore whether a cheese or fermented milk matrix provided best protection during simulated digestion, these strains were added during the manufacture of both products. Potential to survive gastric transit was investigated using the INFOGEST2.0 static digestion model and strains were identified using Pulse-Field Gel Electrophoresis (PFGE). The data obtained demonstrated that Lb. paracasei DPC 7150 and Lb. rhamnosus DPC 7102 persisted in the cheese during ripening and that the Cheddar cheese matrix provided significantly more protection during simulated gastric transit. In order to determine the effects of these lacticaseibacilli-containing Cheddar cheeses in vivo, a short-term feeding study using Black 6 mice was designed to assess cheese intake on the gut microbiome, as well as other parameters of interest. While groups consuming cheese did not differ from the control chow diet in body weight, organ mass, adipose tissue mass, or total plasma cholesterol, differences were observed in plasma triglyceride levels (with those of the Cheddar-consuming groups being significantly higher). The alpha and beta diversity of the gut microbiome, including between certain dietary groups and when compared with their microbial populations prior to commencement of the feeding trial differed significantly. Thus, consumption of Cheddar cheese containing the lacticaseibacilli as adjuncts caused shifts in intestinal microbial populations in comparison in mice even when administered for only 3 weeks. However, in a human study whereby a pre-diabetic cohort was instructed to consume 120 g of commercial Cheddar cheese not containing the lacticaseibacilli adjuncts per day for a 6-week period, no significant differences were observed between the gut microbiome groups prior and post cheese-enriched diet. The overall conclusions from this study are that Cheddar cheese contains a diverse NSLAB population, a significant portion of which can survive gastric transit and display probiotic characteristics. These strains survive during manufacture and ripening of Cheddar cheese and fermented milk and the Cheddar cheese matrix offers good protection during gastric transit. Cheese containing selected strains of lacticaseibacilli as adjuncts can affect the mouse gut microbiome.
Cheddar cheese , Non-starter lactic acid bacteria , Microbiome , Fermented foods , Probiotics
Leeuwendaal, N. K. 2023. Potential of cheddar cheese to impact on the gut microbiota. PhD Thesis, University College Cork.