title: Diversity of microbial communities in open mixed culture fermentations: impact of the pH and carbon source.
abstract: 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.
authors.affiliation: Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.
authors.forename: Margarida F
authors.initials: MF
authors.lastname: Temudo
authors.forename: Gerard
authors.initials: G
authors.lastname: Muyzer
authors.forename: Robbert
authors.initials: R
authors.lastname: Kleerebezem
authors.forename: Mark C M
authors.initials: MC
authors.lastname: van Loosdrecht
mesh_terms: 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
chemical_list: D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012329:RNA, Bacterial; D012336:RNA, Ribosomal, 16S; D002244:Carbon
references.citation: J Appl Microbiol. 2005;99(5):997-1006
references.pmid: 16238731
references.citation: Biotechnol Bioeng. 1977 Aug;19(8):1193-210
references.pmid: 884234
references.citation: Appl Environ Microbiol. 2005 Jul;71(7):3692-700
references.pmid: 16000778
references.citation: Int J Syst Bacteriol. 1994 Oct;44(4):812-26
references.pmid: 7981107
references.citation: Biotechnol Bioeng. 2007 Sep 1;98(1):69-79
references.pmid: 17657773
references.citation: Antonie Van Leeuwenhoek. 1993;63(3-4):299-313
references.pmid: 8279826
references.citation: Curr Microbiol. 2003 Feb;46(2):141-5
references.pmid: 12520370
references.citation: Environ Microbiol. 2007 May;9(5):1112-25
references.pmid: 17472628
references.citation: J Gen Microbiol. 1958 Feb;18(1):259-68
references.pmid: 13525644
references.citation: Appl Environ Microbiol. 2000 Sep;66(9):4058-67
references.pmid: 10966429
references.citation: J Appl Bacteriol. 1977 Aug;43(1):1-24
references.pmid: 332677
references.citation: Bioresour Technol. 2002 May;82(3):209-13
references.pmid: 11991067
references.citation: Curr Opin Biotechnol. 2007 Jun;18(3):207-12
references.pmid: 17509864
references.citation: Arch Microbiol. 1997 Jun;167(6):332-42
references.pmid: 9148774
references.citation: Arch Microbiol. 1995 Sep;164(3):165-72
references.pmid: 7545384
references.citation: Bioresour Technol. 2002 Mar;82(1):87-93
references.pmid: 11858207
references.citation: Can J Microbiol. 1975 Jan;21(1):90-8
references.pmid: 1116041
references.citation: Biotechnol Bioeng. 2006 Feb 20;93(3):592-606
references.pmid: 16273553
references.citation: Nucleic Acids Res. 2004 Feb 25;32(4):1363-71
references.pmid: 14985472
references.citation: J Biotechnol. 2007 May 1;129(3):489-97
references.pmid: 17368850
references.citation: Microbiol Mol Biol Rev. 1998 Sep;62(3):646-66
references.pmid: 9729604
references.citation: Biotechnol Bioeng. 2008 Aug 15;100(6):1088-98
references.pmid: 18553403
references.citation: Bioprocess Biosyst Eng. 2003 Jul;25(6):377-85
references.pmid: 13680343
references.citation: Appl Microbiol Biotechnol. 2004 Dec;66(2):166-73
references.pmid: 15558274
references.citation: Biotechnol Bioeng. 2002 Apr 5;78(1):44-52
references.pmid: 11857280
references.citation: Appl Microbiol Biotechnol. 2001 Nov;57(4):555-62
references.pmid: 11762604
references.citation: Environ Microbiol. 2001 Oct;3(10):649-57
references.pmid: 11722545