M. Vande Woestyne

Development of a 5-step multi-chamber reactor as a simulation of the human intestinal microbial ecosystem.

A five-stage reactor was developed to simulate the gastro-intestinal microbial ecosystem of humans. The small intestine was simulated by a two-step “fill and draw” system, the large intestine by a three-step reactor. A representative supply medium was developed to support a microbial community resembling that of the human gastro-intestinal tract. The entire system was validated by monitoring fermentation fluxes and products, i.e. indicator bacterial groups, volatile fatty acids, enzymatic activities and headspace gases. The simulator was operated with varying concentrations and combinations of arabinogalactan, xylan, pectin, dextrins and starch. The resulting patterns of microbial diversity and activity were analyzed and compared with data for in-vivo gastro-intestinal microbial communities as described in the literature and found to be reprensentative.

Critical Factors Governing the Competitive Behaviour of Lactic Acid Bacteria in Mixed Cultures

The role of lactic acid bacteria in health and disease has been extensively illustrated. Lactic acid bacteria play a major role in the establishment of balanced microbiota in the intestinal tract; their presence provides protection against undesired bacteria. Besides intestinal infections, also urinary tract infections have been successfully prevented by lactic acid bacteria. Their colonisation and proliferation is assumed to depend on their adhesive characteristics. The supply of effective lactic acid organisms is usually provided by lactobacilli-fermented foods. A number of factors substantially influencing the competitive behaviour of lactic acid bacteria in mixed cultures for fermentation purposes as well as for the colonisation of the host animal are discussed in this chapter.

Effect of 2, 2′-dipyridyl on the fermentation pattern of a silage simulation medium contaminated with fecal matter

SummaryThe fermentation pattern of a silage simulation medium contaminated with fecal matter, was followed during 7 days. Iron complexation due to 2,2′-dipyridyl had no negative effect on the growth and the performance of lactic acid bacteria, but Enterobacteriaceae were effectively repressed.

Manganese as a controlling factor in mixed cultures of Lactobacillus plantarum and enterobacteriaceae

Addition of manganese, at levels of 50 ppm, to a liquid growth medium simulating adverse silage conditions had no effect on the growth or on the fermentation pattern of Enterobacter cloacae and Proteus vulgaris. Yet, the manganese strongly enhanced the growth of Lactobacillus plantarum. Co-cultures of L. plantarum and E. cloacae or P. vulgaris were, by addition of manganese ions, significantly altered in the favour of the former. This finding can be of use in mixed cultures where Enterobacteriaceae act as spoiler microorganisms.