A computer-controlled system to simulate conditions of the large intestinewith peristaltic mixing, water absorption and absorption of fermentation products

This paper introduces a new type of system to simulate conditions in the la rge intestine. This system combines removal of metabolites and water with p eristaltic mixing to obtain and handle physiological concentrations of micr oorganisms, dry matter and microbial metabolites. The system has been desig ned to be complementary to the dynamic multi-compartmental system that simu lates conditions in the stomach and small intestine described by Minekus et al. [Minekus M, Marteau P, Havenaar R, Huis in't Veld JHJ (1995) ATLA 23:1 97-209], High densities of microorganisms, comparable to those found in the colon in vivo, were achieved by absorption of water and dialysis of metabo lites through hollow-fibre membranes inside the reactor compartments. The d ense chyme was mixed and transported by peristaltic movements. The potentia l of the system as a tool to study fermentation was demonstrated in experim ents with pectin, fructo-oligosaccharide, lactulose and lactitol as substra tes. Parameters such as total acid production and short-chain fatty acid (S CFA) patterns were determined with time to characterize the fermentation. T he stability of the microflora in the system was tested after inoculation w ith fresh fecal samples and after inoculation with a microflora that was ma intained in a fermenter. Both approaches resulted in total anaerobic bacter ial counts higher than 10(10) colony-forming units/ml with physiological le vels of Bifidobacterium, Lactobacillus, Enterobacteriaceae and Clostridium. The dry matter content was approximately 10%, while the total SCFA concent ration was maintained at physiological concentrations with similar molar ra tios for acetic acid, propionic acid and butyric acid as measured in vivo.