title: Flux analysis of the human proximal colon using anaerobic digestion model 1.
abstract: The colon can be regarded as an anaerobic digestive compartment within the gastro intestinal tract (GIT). An in silico model simulating the fluxes in the human proximal colon was developed on basis of the anaerobic digestion model 1 (ADM1), which is traditionally used to model waste conversion to biogas. Model calibration was conducted using data from in vitro fermentation of the proximal colon (TIM-2), and, amongst others, supplemented with the bio kinetics of prebiotic galactooligosaccharides (GOS) fermentation. The impact of water and solutes absorption by the host was also included. Hydrolysis constants of carbohydrates and proteins were estimated based on total short chain fatty acids (SCFA) and ammonia production in vitro. Model validation was established using an independent dataset of a different in vitro model: an in vitro three-stage continuous culture system. The in silico model was shown to provide quantitative insight in the microbial community structure in terms of functional groups, and the substrate and product fluxes between these groups as well as the host, as a function of the substrate composition, pH and the solids residence time (SRT). The model confirms the experimental observation that methanogens are washed out at low pH or low SRT-values. The in silico model is proposed as useful tool in the design of experimental setups for in vitro experiments by giving insight in fermentation processes in the proximal human colon.
authors.affiliation: Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628BC Delft, The Netherlands; FrieslandCampina, Stationsplein 4, 3818 LE Amersfoort, The Netherlands. Electronic address: wagenaar.am@gmail.com.
authors.forename: Anne Marieke
authors.initials: AM
authors.lastname: Motelica-Wagenaar
authors.affiliation: FrieslandCampina, Stationsplein 4, 3818 LE Amersfoort, The Netherlands. Electronic address: arjen.nauta@frieslandcampina.com.
authors.forename: Arjen
authors.initials: A
authors.lastname: Nauta
authors.affiliation: FrieslandCampina, Stationsplein 4, 3818 LE Amersfoort, The Netherlands; EMGO Institute for Health and Care Research, Department of Epidemiology and Biostatistics, Van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands. Electronic address: ellen.vandenheuvel@frieslandcampina.com.
authors.forename: Ellen G H M
authors.initials: EG
authors.lastname: van den Heuvel
authors.affiliation: Delft University of Technology, Department of Biotechnology, Julianalaan 67, 2628BC Delft, The Netherlands. Electronic address: R.kleerebezem@tudelft.nl.
authors.forename: Robbert
authors.initials: R
authors.lastname: Kleerebezem
mesh_terms: D000641:Ammonia / Q000032:analysis; D001421:Bacteria, Anaerobic / Q000254:growth & development* / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D003106:Colon / Q000382:microbiology* / Q000502:physiology*; D003198:Computer Simulation; D004063:Digestion; D005227:Fatty Acids / Q000032:analysis; D006801:Humans; D006868:Hydrolysis; D008962:Models, Theoretical; D011506:Proteins / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D011506:Proteins; D000641:Ammonia
keywords: Anaerobic digestion; Human colon; Microbiota; Modeling; SCFA's