title: CO₂ /HCO₃⁻ perturbations of simulated large scale gradients in a scale-down device cause fast transcriptional responses in Corynebacterium glutamicum.
abstract: The exploration of scale-down models to imitate the influence of large scale bioreactor inhomogeneities on cellular metabolism is a topic with increasing relevance. While gradients of substrates, pH, or dissolved oxygen are often investigated, oscillating CO2/HCO3 (-) levels, a typical scenario in large industrial bioreactors, is rarely addressed. Hereby, we investigate the metabolic and transcriptional response in Corynebacterium glutamicum wild type as well as the impact on L-lysine production in a model strain exposed to pCO2 gradients of (75-315) mbar. A three-compartment cascade bioreactor system was developed and characterized that offers high flexibility for installing gradients and residence times to mimic industrial-relevant conditions and provides the potential of accurate carbon balancing. The phenomenological analysis of cascade fermentations imposed to the pCO2 gradients at industry-relevant residence times of about 3.6 min did not significantly impair the process performance, with growth and product formation being similar to control conditions. However, transcriptional analysis disclosed up to 66 differentially expressed genes already after 3.6 min under stimulus exposure, with the overall change in gene expression directly correlateable to the pCO2 gradient intensity and the residence time of the cells.
authors.affiliation: Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569, Stuttgart, Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Buchholz
authors.forename: Michaela
authors.initials: M
authors.lastname: Graf
authors.forename: Andreas
authors.initials: A
authors.lastname: Freund
authors.forename: Tobias
authors.initials: T
authors.lastname: Busche
authors.forename: Jörn
authors.initials: J
authors.lastname: Kalinowski
authors.forename: Bastian
authors.initials: B
authors.lastname: Blombach
authors.forename: Ralf
authors.initials: R
authors.lastname: Takors
mesh_terms: D001639:Bicarbonates / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology; D002245:Carbon Dioxide / Q000378:metabolism*; D065098:Catechol O-Methyltransferase Inhibitors; D048230:Corynebacterium glutamicum / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media / Q000737:chemistry; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D008239:Lysine / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001639:Bicarbonates; D065098:Catechol O-Methyltransferase Inhibitors; D003470:Culture Media; D002245:Carbon Dioxide; D008239:Lysine