title: Respiration activity monitoring system for any individual well of a 48-well microtiter plate.
abstract: BACKGROUND
  Small-scale micro-bioreactors have become the cultivation vessel of choice during the first steps of bioprocess development. They combine high cultivation throughput with enhanced cost efficiency per cultivation. To gain the most possible information in the early phases of process development, online monitoring of important process parameters is highly advantageous. One of these important process parameters is the oxygen transfer rate (OTR). Measurement of the OTR, however, is only available for small-scale fermentations in shake flasks via the established RAMOS technology until now. A microtiter plate-based (MTP) μRAMOS device would enable significantly increased cultivation throughput and reduced resource consumption. Still, the requirements of miniaturization for valve and sensor solutions have prevented this transfer so far. This study reports the successful transfer of the established RAMOS technology from shake flasks to 48-well microtiter plates. The introduced μRAMOS device was validated by means of one bacterial, one plant cell suspension culture and two yeast cultures.
  
  
  RESULTS
  A technical solution for the required miniaturized valve and sensor implementation for an MTP-based μRAMOS device is presented. A microfluidic cover contains in total 96 pneumatic valves and 48 optical fibers, providing two valves and one optical fiber for each well. To reduce costs, an optical multiplexer for eight oxygen measuring instruments and 48 optical fibers is introduced. This configuration still provides a reasonable number of measurements per time and well. The well-to-well deviation is investigated by 48 identicalEscherichia colicultivations showing standard deviations comparable to those of the shake flask RAMOS system. The yeastHansenula polymorphaand parsley suspension culture were also investigated.
  
  
  CONCLUSIONS
  The introduced MTP-based μRAMOS device enables a sound and well resolved OTR monitoring for fast- and slow-growing organisms. It offers a quality similar to standard RAMOS in OTR determination combined with an easier handling. The experimental throughput is increased 6-fold and the media consumption per cultivation is decreased roughly 12.5-fold compared to the established eight shake flask RAMOS device.
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: David
authors: D
authors: Flitsch
authors: KEμ, Konstruktion und Entwicklung von Mikrosystemen, RWTH Aachen University, Steinbachstraße 53b, 52074 Aachen, Germany.
authors: Sebastian
authors: S
authors: Krabbe
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: Tobias
authors: T
authors: Ladner
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: Mario
authors: M
authors: Beckers
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: Jana
authors: J
authors: Schilling
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: Stefan
authors: S
authors: Mahr
authors: Institute of Plant Physiology, Aachen Biology and Biotechnology, RWTH Aachen University, 1 Worringer Weg, Aachen, 52074 Germany.
authors: Uwe
authors: U
authors: Conrath
authors: KEμ, Konstruktion und Entwicklung von Mikrosystemen, RWTH Aachen University, Steinbachstraße 53b, 52074 Aachen, Germany.
authors: Werner K
authors: WK
authors: Schomburg
authors: AVT - Aachener Verfahrenstechnik, Biochemical Engineering, RWTH Aachen University, Worringer Weg 1, 52074 Aachen, Germany.
authors: Jochen
authors: J
authors: Büchs
keywords: High throughput; Microtiter plate (MTP); Oxygen transfer rate (OTR); RAMOS; μRAMOS