title: Scale-up bioprocess development for production of the antibiotic valinomycin in Escherichia coli based on consistent fed-batch cultivations.
abstract: BACKGROUND
  Heterologous production of natural products in Escherichia coli has emerged as an attractive strategy to obtain molecules of interest. Although technically feasible most of them are still constrained to laboratory scale production. Therefore, it is necessary to develop reasonable scale-up strategies for bioprocesses aiming at the overproduction of targeted natural products under industrial scale conditions. To this end, we used the production of the antibiotic valinomycin in E. coli as a model system for scalable bioprocess development based on consistent fed-batch cultivations.
  
  
  RESULTS
  In this work, the glucose limited fed-batch strategy based on pure mineral salt medium was used throughout all scales for valinomycin production. The optimal glucose feed rate was initially detected by the use of a biocatalytically controlled glucose release (EnBase® technology) in parallel cultivations in 24-well plates with continuous monitoring of pH and dissolved oxygen. These results were confirmed in shake flasks, where the accumulation of valinomycin was highest when the specific growth rate decreased below 0.1 h(-1). This correlation was also observed for high cell density fed-batch cultivations in a lab-scale bioreactor. The bioreactor fermentation produced valinomycin with titers of more than 2 mg L(-1) based on the feeding of a concentrated glucose solution. Valinomycin production was not affected by oscillating conditions (i.e. glucose and oxygen) in a scale-down two-compartment reactor, which could mimic similar situations in industrial bioreactors, suggesting that the process is very robust and a scaling of the process to a larger industrial scale appears a realistic scenario.
  
  
  CONCLUSIONS
  Valinomycin production was scaled up from mL volumes to 10 L with consistent use of the fed-batch technology. This work presents a robust and reliable approach for scalable bioprocess development and represents an example for the consistent development of a process for a heterologously expressed natural product towards the industrial scale.
authors.affiliation: Chair of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Ackerstraße 76, ACK24, 13355, Berlin, Germany. ljtboa@gmail.com.|Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL, 60208, USA. ljtboa@gmail.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Li
authors.affiliation: Chair of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Ackerstraße 76, ACK24, 13355, Berlin, Germany. jennifer.jaitzig@gmx.net.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Jaitzig
authors.affiliation: Chair of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Ackerstraße 76, ACK24, 13355, Berlin, Germany. judyluping@hotmail.com.
authors.forename: Ping
authors.initials: P
authors.lastname: Lu
authors.affiliation: Department of Chemistry, Technische Universität Berlin, Straße des 17. Juni 124, 10623, Berlin, Germany. roderich.suessmuth@tu-berlin.de.
authors.forename: Roderich D
authors.initials: RD
authors.lastname: Süssmuth
authors.affiliation: Chair of Bioprocess Engineering, Department of Biotechnology, Technische Universität Berlin, Ackerstraße 76, ACK24, 13355, Berlin, Germany. peter.neubauer@tu-berlin.de.
authors.forename: Peter
authors.initials: P
authors.lastname: Neubauer
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D061249:Batch Cell Culture Techniques / Q000295:instrumentation / Q000379:methods*; D019149:Bioreactors / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D014634:Valinomycin / Q000096:biosynthesis*
chemical_list: D000900:Anti-Bacterial Agents; D014634:Valinomycin; D005947:Glucose