Healthy gut ecosystems

With a one vessel fermentor (BioFlo 110, New Brunswick), an in vitro simulation of a certain part of the gastrointestinal tract (e.g. cecum, colon) is performed. In this fermentation system, physiological gut parameters (pH, temperature) are kept constant, while chemico-physical characteristics of the gut chime are simulated by adding pork mucin and fibre to the fermentation medium. For a first screening, the fermentation system can be performed in short time (24-48 h) batch mode. The system is inoculated with cecal or fecal material from animals or humans, and can be inoculated with a pathogen like Salmonella. Batch fermentations are monitored by periodic sampling on a quantitative level by dilution plating on selective media for certain bacterial groups (e.g. lactic acid bacteria, bifidobacteria, Enterobacteriaceae, clostridia) as well as for Salmonella, and on a qualitative level for the total microbiota by cultivation independent 16S rDNA based metagenomics; production of short chain fatty acids is measured by GC. From these batch fermentations, for more detailed investigation long-term (up to 2 weeks) a continuous fermentation system is used which simulates even better the gastrointestinal tract of monogastrics like the pig because it takes into account the retention time (or conversely flow of intestinal content) in a certain part of the gut. A continuous fermentation is started in batch mode as described above after which fresh medium is added with a peristaltic pump to the fermentor vessel at a fixed dilution speed and fermented medium is wasted with the same speed to maintain the medium volume in the vessel. After a few days, a steady state is reached and bacteriological and fatty acid parameters can be monitored over several days (or weeks) as described above. All fermentations (batch and continuous) are performed at least twice and for every condition or component, a blank fermentation is included.