Abstract Bachelor Project FBT 2020-2021: Investigation of prebiotics in infants microbiota Simulator of the Human Intestinal Microbial Ecosystem (SHIME)
It is known that the metabolites formed after digestion in the gastrointestinal tract have a lot of impact on the health of the host. Some metabolites like butyrate can act as an energy source for bacteria situated in the colon. Other metabolites like ammonia can have a negative impact on the host, as in high concentrations it is toxic for the central nervous system. In this research four prebiotics were tested in the simulated gastrointestinal tract of a baby donor. Prebiotics are substrates which stimulate the growth of favourable bacteria like the Bifidobacterium species, so pathogenic bacteria are outnumbered. The prebiotics were tested via an in vitro simulation platform, called the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The SHIME was inoculated with an inoculum of a baby donor. After the inoculation, the system underwent a stabilization period. Subsequent a control period followed, where the basic values of short chain fatty acids (SCFA), lactate and ammonium were determined. SCFA were analysed by a gas chromatographic method after carrying out a liquid-liquid extraction (LLE). Lactate on the other hand was analysed using an enzymatic procedure, while ammonium was analysed by carrying out a steam distillation followed by titration. Following the control period, a treatment period of three weeks was initiated, where the prebiotic test compounds were administered into the SHIME. In this period the same metabolites were analysed in order to analyse the effect of the test products on the microbial metabolic activity of the microbial community. It was observed that PreBio1 caused an increase in acetate levels in the proximal (PC) and distal colon (DC). However, propionate concentrations remained unaffected, while butyrate was only positively affected in the DC by PreBio1. The treatment with PreBio2 stimulated acetate and butyrate levels in PC and DC, while propionate mainly increased in the DC. PreBio3 on the other hand boosted acetate and decreased propionate production in PC and DC, while butyrate was only improved in the DC. By adding PreBio4, acetate concentrations enhanced in the PC and DC, whereas production of propionate remained unaffected and butyrate levels only increased in the DC. The lactate levels in the PC decreased during the treatment period upon supplementation of PreBio1, PreBio2 and PreBio3. No changes were seen in PC after administration of PreBio4 and also no changes were observed in the DC for all prebiotic treatments. Finally, the amount of ammonium increased in both the PC and DC by administering PreBio2, PreBio3 and PreBio4. PreBio1 on the other hand didn’t cause any significant change in ammonium levels. Overall, it can be concluded that all prebiotic test compounds enhanced the production of acetate, indicating fermentation of the prebiotics by the microbial community of the baby donor. Furthermore, the reduction in lactate levels for most test products coupled with the stimulation of butyrate concentrations indicated that lactate-consuming butyrate-producing microbial groups were probably stimulated by the addition of the prebiotic compounds. Finally, some product-specific findings included the stimulation of propionate production by PreBio2 and the absence of ammonium increases by supplementing PreBio1.
Abstract Bachelor Project FBT 2019-2020: Prebiotic properties of oat fibres in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)
The microbial community in the gastrointestinal tract has a big influence on the hosts health by the different metabolites they produce. Some beneficial metabolites such as butyrate which act as an energy source and reduce gastrointestinal inflammation, some detrimental metabolites like ammonium which increases the risk of colon cancer. In this thesis the effects of three different oat fibres were tested on the production of these microbial metabolites. The test products were tested with the in vitro simulation platform, the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The SHIME was inoculated with the faecal inoculum of one donor and stabilised for two weeks after which a two-week control period was set up. Lastly a treatment period followed and lasted three weeks. Samples for short chain fatty acid (SCFA), lactate and ammonium analysis were taken three times a week from both proximal and distal colon reactors starting from the control weeks. The SCFA were analysed with the help of gas chromatography, lactate was determined with an enzymatic method and ammonium was determined through a combination of steam distillation and titration. For all oat fibres, prebiotic effects were registered with an increase for all metabolites for oat fibre 1 and 3. However for oat fibre 2 an increase for SCFA and lactate combined with a decrease in ammonium production was observed. The decrease in ammonium production is most likely the effect of a higher concentration of carbohydrates in the oat fibre. In future research the reduction in ammonium can be further investigated together with an inquiry which oat fibre stimulates which group of microorganisms.
Abstract Bachelor Project FBT 2018-2019: Evaluation of the effect of oat fibers in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®)
It is known that metabolites produced by gut bacteria have an effect on host’s health. For example, short chain fatty acids provide energy to the epithelial cells in the gut and have been linked with several health-promoting properties. Butyrate, in particular, has immunomodulatory potential and has been associated with cancer prevention. Several studies have therefore explored the potential improvement of health by modulating the gut microbiota, with the main focus on pre- and probiotics. In this thesis, the effect of a low concentration of a test product containing oat fibers on the gut microbiota of three different donors was evaluated. The evaluation was performed in the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®). Each SHIME unit consisted of a succession of reactor vessels which represent the stomach, small intestine, proximal and distal colon. The proximal and distal colon were inoculated with a fecal inoculum obtained from a single donor. For two weeks, control samples were taken to obtain baseline values in terms of microbial activity. During the next six weeks, the SHIME units were treated repeatedly with the test product. Three times per week samples from the proximal and distal SHIME vessels were taken for short chain fatty acid (SCFA), lactate and ammonium analysis. Supplementation of the test product resulted in an increase of SCFA, lactate and ammonium concentrations compared to the control period for all donors tested. The increase in SCFA and lactate concentrations suggested that the test product has a prebiotic potential, while the increase in ammonium levels suggested enhancement of proteolytic fermentation. Indeed, because a low amount of test product was administered, this probably caused a fast depletion of carbohydrates in the product, leading to microbial fermentation of the additional proteins in the product. In the future, a higher concentration of test product could be tested, in order to determine if this could limit ammonium increase and to prove consistency of prebiotic potential.