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AuthorDempf, Stefandc.contributor.author
Date of accession2016-03-14T15:20:21Zdc.date.accessioned
Available in OPARU since2016-03-14T15:20:21Zdc.date.available
Year of creation2007dc.date.created
AbstractStreptococcus thermophilus is a Gram-positive, anaerobic but aerotolerant organism and widely used in dairy industry in starter cultures. This dissertation describes the construction and characterization of a S. thermophilus strain with improved osmotic tolerance and advanced carbon flux to lactate. The mutant strain S. thermophilus delta-proBA was constructed by deletion of the proline biosynthesis genes proB and proA. This strain did not show any difference in growth and acidification in complex medium, in chemically defined medium the mutant was proline-auxotrophic. Characterization of S. thermophilus delta-proBA under osmotic stress conditions showed a higher osmotolerance for this strain when compared to the parental strain. Based on the inactivated proline biosynthesis it was suggested that the mutant strain would show a reduced phage sensitivity. However, contrary to the expectations, no difference in phage sensitivity was detected with S. thermophilus delta-proBA when compared to the parental strain. Overproduction of the lactate dehydrogenase (LDH) in S. thermophilus delta-proBA resulted in a significantly higher specific LDH activity, leading to a more efficient acidification. Heterologous overproduction of the PEP synthetase (PPS) of Escherichia coli introduced PPS activity which led to a further increase of specific lactate synthesis, most probably by induction of a so-called "futile cycle", connected with higher lactose consumption. The rise of specific lactate synthesis was also clearly present under conditions of osmotic stress, but combined with a reduced acidification rate. With a higher inoculum the acidification rate under osmotic stress conditions was enhanced. Additionally the strain showed a very limited growth, which might result in a reduced phage sensitivity.dc.description.abstract
Languagededc.language.iso
PublisherUniversität Ulmdc.publisher
LicenseStandard (Fassung vom 03.05.2003)dc.rights
Link to license texthttps://oparu.uni-ulm.de/xmlui/license_v1dc.rights.uri
KeywordCarbon fluxdc.subject
KeywordOsmotic stressdc.subject
KeywordProlinedc.subject
Dewey Decimal GroupDDC 570 / Life sciencesdc.subject.ddc
LCSHCaptoprildc.subject.lcsh
LCSHStreptococcus thermophilusdc.subject.lcsh
TitleKonstruktion und Charakterisierung eines Streptococcus thermophilus-Stammes mit erhöhter Osmotoleranz und gesteigertem Kohlenstofffluss in Richtung Laktatdc.title
Resource typeDissertationdc.type
DOIhttp://dx.doi.org/10.18725/OPARU-1112dc.identifier.doi
URNhttp://nbn-resolving.de/urn:nbn:de:bsz:289-vts-61031dc.identifier.urn
GNDOsmophiliedc.subject.gnd
FacultyFakultät für Naturwissenschaftenuulm.affiliationGeneral
Date of activation2007-12-16T22:11:09Zuulm.freischaltungVTS
Peer reviewneinuulm.peerReview
Shelfmark print versionZ: J-H 11.681 ; W: W-H 9.881uulm.shelfmark
DCMI TypeTextuulm.typeDCMI
VTS-ID6103uulm.vtsID
CategoryPublikationenuulm.category
University Bibliographyjauulm.unibibliographie


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