title: Bioprocess control in microscale: scalable fermentations in disposable and user-friendly microfluidic systems.
abstract: BACKGROUND
  The efficiency of biotechnological production processes depends on selecting the best performing microbial strain and the optimal cultivation conditions. Thus, many experiments have to be conducted, which conflicts with the demand to speed up drug development processes. Consequently, there is a great need for high-throughput devices that allow rapid and reliable bioprocess development. This need is addressed, for example, by the fiber-optic online-monitoring system BioLector which utilizes the wells of shaken microtiter plates (MTPs) as small-scale fermenters. To further improve the application of MTPs as microbioreactors, in this paper, the BioLector technology is combined with microfluidic bioprocess control in MTPs. To realize a user-friendly system for routine laboratory work, disposable microfluidic MTPs are utilized which are actuated by a user-friendly pneumatic hardware.
  
  
  RESULTS
  This novel microfermentation system was tested in pH-controlled batch as well as in fed-batch fermentations of Escherichia coli. The pH-value in the culture broth could be kept in a narrow dead band of 0.03 around the pH-setpoint, by pneumatically dosing ammonia solution and phosphoric acid to each culture well. Furthermore, fed-batch cultivations with linear and exponential feeding of 500 g/L glucose solution were conducted. Finally, the scale-up potential of the microscale fermentations was evaluated by comparing the obtained results to that of fully controlled fermentations in a 2 L laboratory-scale fermenter (working volume of 1 L). The scale-up was realized by keeping the volumetric mass transfer coefficient kLa constant at a value of 460 1/h. The same growth behavior of the E. coli cultures could be observed on both scales.
  
  
  CONCLUSIONS
  In microfluidic MTPs, pH-controlled batch as well as fed-batch fermentations were successfully performed. The liquid dosing as well as the biomass growth kinetics of the process-controlled fermentations agreed well both in the microscale and laboratory scale. In conclusion, a user-friendly and disposable microfluidic system could be established which allows scaleable, fully controlled and fully monitored fermentations in working volumes below 1 milliliter.
authors.affiliation: AVT-Biochemical Engineering, RWTH Aachen University, Worringerweg 1, D-52074 Aachen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Funke
authors.forename: Andreas
authors.initials: A
authors.lastname: Buchenauer
authors.forename: Wilfried
authors.initials: W
authors.lastname: Mokwa
authors.forename: Stefanie
authors.initials: S
authors.lastname: Kluge
authors.forename: Lea
authors.initials: L
authors.lastname: Hein
authors.forename: Carsten
authors.initials: C
authors.lastname: Müller
authors.forename: Frank
authors.initials: F
authors.lastname: Kensy
authors.forename: Jochen
authors.initials: J
authors.lastname: Büchs
mesh_terms: D000641:Ammonia / Q000494:pharmacology; D004926:Escherichia coli / Q000254:growth & development; D005285:Fermentation; D005947:Glucose / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D008904:Miniaturization; D010756:Phosphoric Acids / Q000494:pharmacology
chemical_list: D010756:Phosphoric Acids; D000641:Ammonia; C030242:phosphoric acid; D005947:Glucose