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.