Diversity of microbial communities in open mixed culture fermentations: impact of the pH and carbon source.
Anaerobic fermentation by an open mixed culture was investigated at different pH values (4-8.5) and with three substrates (glucose, glycerol and xylose). The populations established in each condition were assessed by denaturing gradient gel electrophoresis analysis of the 16S ribosomal RNA gene fragments. The fermentation pattern and the composition of the microbial population were also evaluated when operational variations were imposed (increase of substrate concentration or introduction of a second substrate). The experimental results demonstrated that at low and high pH values, a clearly different fermentation pattern was associated with the dominance of a specialised group of clostridiae. At intermediate pH values, the product spectrum was rather variable and seemed to be sensitive to variations in the microbial community. Different substrates resulted in the establishment of different microbial communities. When fed with a mixture of two substrates, mixotrophic microorganisms (capable of degrading both substrates) were found to overgrow the originally dominant specialists. Overall, the experiments have shown that some operational variables have a clear impact on the fermentation pattern and on the population established. However, a uniform relationship between the process characteristics (associated to a metabolic response) and the microbial population present is not always possible.
Temudo
Margarida F
MF
Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
Muyzer
Gerard
G
Kleerebezem
Robbert
R
van Loosdrecht
Mark C M
MC
D000693:Anaerobiosis; D044822:Biodiversity; D019149:Bioreactors / Q000382:microbiology*; D002244:Carbon / Q000378:metabolism*; D016172:DNA Fingerprinting; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005285:Fermentation; D020459:Genes, rRNA; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009691:Nucleic Acid Denaturation; D010802:Phylogeny; D012329:RNA, Bacterial / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D002244:Carbon
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