Models for intestinal fermentation: association between food components, delivery systems, bioavailability and functional interactions in the gut.

There is increasing interest in the human colonic microbiota and in the way its metabolic activities impact on host health and well-being. For most practical purposes, however, the large bowel is inaccessible for routine investigation, and a variety of animal and in vitro model systems have been developed to study the microbiota. In vitro models range from simple closed systems using pure or defined mixed populations of bacteria, or faecal material, to more sophisticated complex multistage continuous cultures that are able to simulate many of the spatial, temporal and environmental attributes that characterize microbiological events in different regions of the large gut. Recent developments using these systems have enabled modelling of surface colonisation and biofilm development, a hitherto neglected area of study.