Browsing by Author "El-Mamouni, R."

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Characterization of different microbial nuclei as potential precursors of anaerobic granulation
(1995-05) El-Mamouni, R.; Gulot, S. R.; Leduc, R.; Costerton, J. William
Anaerobic granule nuclei enriched in either acidogens, syntrophic consortia, Methanosaeta spp. or Methanosarcina spp. were developed in four upflow bed filter reactors fed with sucrose, an ethanol/acetate mixture, acetate and methanol, respectively. The enrichment process was evaluated by scanning electron microscopy and by the change in trophic specific activities. The four developed granule nuclei presented different settling velocities: 3.2, 8.7, 10.5 and 11.3 m h−1 for the acidogenic floes, the Methanosarcina-, the syntrophic consortia and the Methanosaeta-enriched nuclei, respectively. These velocities were related to the size and the ash content of the various aggregates. Acidogenic floes were relatively small in size ( < 0.6 mm in diameter), compared to the other granule nuclei (up to 1.2 mm in diameter). The ash content represented 60%, 40%, 30% and 16% for Methanosaeta-, Methanosarcina-enriched nuclei, syntrophic consortia and acidogenic floes, respectively. Methanosaeta-enriched nuclei contained high amounts of Ca2+ (140 mg per g SS) compared to the other ones (1–8 mg per g SS). Acidogenic floes contained high amount of extracellular polymeric substances compared to the other types of nuclei.
Influence of the microbial content of different precursory nuclei on the anaerobic granulation dynamics
(1995) El-Mamouni, R.; Leduc, R.; Costerton, J. William; Gulot, S. R.
Anaerobic granule nuclei enriched in either acidogens (AF), syntrophic consortia (SN), Methanosaeta spp. (MT) and Methanosarcina spp. (MN) were developed in four upflow bed filter reactors fed with sucrose, an ethanol/acetate mixture, acetate and methanol, respectively. The four developed granule nuclei presented different settling velocities: 3.2, 8.7, 10.5 and 11.3 m/h for the AF flocs, the MS-, the SN- and the MT-nuclei, respectively. The ash content represented 60%, 40%, 30% and 16% of dry weight for the MT-, MS-, SN-enriched nuclei, and AF flocs, respectively. Acidogenic flocs contained high amount of extracellular polymeric substances. The influence of these four different nuclei on the time course of complex granule development was investigated by shifting the feed carbon of all of the four reactors to sucrose. Granulation proceeded rapidly both on syntrophic and Methanosaeta nuclei. The largest granules (Sauter diameter of 2.36 mm), however, were obtained within the shortest period in the reactor started with syntrophic nuclei. These nuclei presented also the best colonization by fermentative bacteria as shown by the evolution of their glucotrophic activities. Less satisfying granulation was obtained on Methanosarcina nuclei. In contrast, granulation was significantly retarded when acidogens were used as precursors. From these results it appears that syntrophs and Methanosaeta spp. play the principal role in anaerobic granulation process.