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@PHDTHESIS{Hoffmann:995158,
      author       = {Hoffmann, Kyra},
      othercontributors = {Büchs, Jochen and Conrath, Uwe},
      title        = {{O}nline analysis of microbial γ-polyglutamic acid
                      production and plant defense priming in small-scale cell
                      culture},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      publisher    = {RWTH Aachen University},
      reportid     = {RWTH-2024-09757},
      pages        = {1 Online-Ressource : Illustrationen},
      year         = {2024},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, Rheinisch-Westfälische Technische
                      Hochschule Aachen, 2024},
      abstract     = {The development of online analytical tools significantly
                      accelerates research of bioprocesses in small shaken
                      cultures. This thesis demonstrates the application of online
                      analytics for two processes. Firstly for the production of
                      poly--glutamic acid (γ-PGA) in shake flasks and secondly
                      for the detection of priming-active compounds with parsley
                      cell cultures in microtiter plates. These two diverse
                      research topics demonstrate the power of online analytic
                      tools in small culture scale. The first chapter of this
                      thesis is about the online screening of γ-PGA, a biopolymer
                      with a wide range of applications. The γ-PGA was produced
                      with genetically modified Bacillus subtilis 168 strains. The
                      formation and concomitant secretion of γ-PGA increase the
                      culture broth viscosity, while enzymatic depolymerization
                      and degradation of γ-PGA by native depolymerases decrease
                      the viscosity. The viscosity monitoring online system
                      (ViMOS) was applied for optical online measurements of broth
                      viscosity in shake flasks. This online monitoring enabled
                      the analysis of the promoter Ppst in combination with
                      different γ PGA depolymerase and by-product knockout
                      mutants in genetically modified B. subtilis 168 strains. The
                      different single depolymerase knockout mutants were ∆ggt,
                      ∆pgdS, ∆cwlO, and a triple knockout mutant.
                      Additionally, to the Ppst promoter, the γ-PGA production
                      under the control of the Pxyl promoter was analyzed. An
                      increase in γ-PGA yield in gγ PGA/gglucose of $190\%$
                      could be achieved with the triple knockout mutant compared
                      to the Ppst reference strain. The strain with the Pxyl
                      promoter produced even 8.4 gγ-PGA/molcarbon. This is a
                      higher γ-PGA yield than achieved using the glutamic
                      acid-dependent γ-PGA producer Bacillus licheniformis ATCC
                      9945. Therefore, Bacillus subtilis Pxyl is a promising
                      candidate for γ-PGA production with glucose as the sole
                      carbon source. The second chapter of this thesis presents a
                      biochemical approach to detect defense priming in parsley
                      cell cultures in microtiter plates. Conventional crop
                      protection has major drawbacks, such as developing pest and
                      pathogen insensitivity to pesticides and low environmental
                      compatibility. Therefore, alternative crop protection
                      strategies are needed. One approach treats crops with
                      chemical compounds that induce a primed state of enhanced
                      defense. Online identification of priming-inducing chemistry
                      by recording breathing activity with the oxygen transfer
                      rate (OTR) represents a highly informative approach to spot
                      priming-activating chemistry. This thesis shows the online
                      measurement of the dissolved oxygen tension (DOT) in
                      microtiter plates (MTPs) and the calculation of the OTR from
                      the DOT to be a valid tool to draw conclusions regarding
                      priming-inducing activity. Furthermore, the fluorescence of
                      the priming-active reference compound salicylic acid (SA)
                      and furanocoumarins was simultaneously monitored online in
                      MTPs. Determining the OTR, fluorescence of the
                      priming-active chemical compound SA, and furanocoumarins in
                      parsley suspension cultures in MTPs by online measurement
                      allows an in-depth screening for priming compounds and a
                      better understanding of the priming process induced by a
                      given substance.},
      cin          = {416510 / 161620 / 161710},
      ddc          = {620},
      cid          = {$I:(DE-82)416510_20140620$ / $I:(DE-82)161620_20140620$ /
                      $I:(DE-82)161710_20140620$},
      pnm          = {SeleCa - Selectivity in Chemo- and Biocatalysis (SeleCa)
                      (SELECA-20170406) / Doktorandenprogramm
                      (PHD-PROGRAM-20170404)},
      pid          = {G:(DE-Juel1)SELECA-20170406 /
                      G:(DE-HGF)PHD-PROGRAM-20170404},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2024-09757},
      url          = {https://publications.rwth-aachen.de/record/995158},
}