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@PHDTHESIS{Lechtenberg:1034398,
      author       = {Lechtenberg, Thorsten},
      title        = {{T}olerance engineering of {P}seudomonas for the efficient
                      conversion and production of aldehydes},
      volume       = {292},
      school       = {Düsseldorf},
      type         = {Dissertation},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2024-07180},
      isbn         = {978-3-95806-817-9},
      series       = {Schriften des Forschungszentrums Jülich Reihe
                      Schlüsseltechnologien / Key Technologies},
      pages        = {XVI, 185},
      year         = {2025},
      note         = {Dissertation, Düsseldorf, 2024},
      abstract     = {Biocatalysis holds promise to tackle the sustainability
                      challenges faced by chemical industry due to climate change
                      and depletion of fossil resources. However, obstacles emerge
                      regarding the compatibility of several important chemicals,
                      notably aldehydes, with biological systems, even if
                      remarkably robust workhorses such as bacteria of the
                      Pseudomonas clade are employed. This is related to the high
                      and versatile reactivity of aldehydes, which is both their
                      greatest asset and the root cause of their toxicity.
                      Competitive biocatalytic processes involving these
                      substances thus require tolerance-improved host organisms.
                      In view of the constantly growing demand for renewable and
                      ecologically produced plastics, the biocatalytic oxidation
                      of the burgeoning platform chemical
                      5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic
                      acid (FDCA) is of particular interest since FDCA can
                      substitute structurally similar and fossilbased terephthalic
                      acid in polyesters. With the periplasmic oxidoreductase
                      complex PaoEFG and the cytoplasmic dehydrogenases AldB-I and
                      AldB-II, the primary enzymes responsible for the oxidation
                      of HMF and further aromatic aldehydes like
                      4-hydroxybenzaldehyde and vanillin by P. taiwanensis VLB120
                      and P. putida KT2440 were uncovered. This marks a
                      significant advancement from former black-box application of
                      these strains to specialized biocatalysts with fine-tuned
                      properties. To illustrate, overexpression of the newly
                      characterized genes resulted in so-called BOX-strains
                      (Boosted OXidation) with up to tenfold increased initial
                      oxidation rates in comparison to the wild type. As a result,
                      the new variants exhibited increased robustness when growing
                      in presence of HMF and also proved to be more efficient for
                      the complete oxidation of the aldehyde to the industrial
                      target compound FDCA. Furthermore, tolerance mechanisms
                      distinct from rapid oxidation were sought applying an
                      adaptive laboratory evolution approach. A ROX (Reduced
                      OXidation) deletion mutant with diminished aldehyde
                      conversion ability was subjected to steady HMF stress. This
                      yielded toleranceimproved strains through the unforeseen
                      inactivation of the regulator MexT and the associated
                      shutdown of the efflux pump MexEF-OprN. Another potential
                      use for oxidation-deficient, yet solvent-tolerant,
                      Pseudomonads is the biosynthesis of aromatic aldehydes, as
                      showcased with the popular aroma compound t-cinnamaldehyde.
                      In conclusion, this thesis contributes to the fundamental
                      understanding of aromatic aldehyde conversion by P.
                      taiwanensis VLB120 and P. putida KT2440 by unveiling the
                      underlying enzymes which were shown to constitute the
                      organisms’ main tolerance mechanism against these toxic
                      substances. Their overexpression in BOX strains strongly
                      increases aldehyde tolerance, and enables improved FDCA
                      production by boosted HMF oxidation. Reduced aldehyde
                      oxidation and reduction (ROAR) unlocks P. taiwanensis VLB120
                      for the (de novo) production of valuable aromatic aldehydes
                      or aldehyde-derived products, thereby expanding the product
                      portfolio of this aspiring microbial cell factory.},
      cin          = {IBG-1},
      cid          = {I:(DE-Juel1)IBG-1-20101118},
      pnm          = {2172 - Utilization of renewable carbon and energy sources
                      and engineering of ecosystem functions (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2172},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:0001-2505050903420.294942610928},
      doi          = {10.34734/FZJ-2024-07180},
      url          = {https://juser.fz-juelich.de/record/1034398},
}