no concomitant increase of the Salmonella or coliform population was observed while propionic, butyric and lactic acid production returned to their initial levels. Cultivation-independent microbial community analysis via PCR-DGGE for this experiment is shown in Fig. 2. At day 1 (directly after the start of continuous culture) equilibrium was obviously not reached yet, as shown by a community pattern quite distinct from all later samples.