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Regensburg, Germany

Janzen N.H.,TU Munich | Schmidt M.,TU Munich | Krause C.,PreSens Precision Sensing GmbH | Weuster-Botz D.,TU Munich
Bioprocess and Biosystems Engineering

Optical chemical sensors are the standard for pH monitoring in small-scale bioreactors such as microtiter plates, shaking flasks or other single-use bioreactors. The dynamic pH range of the so far commercially available fluorescent pH sensors applied in small-scale bioreactors is restricted to pH monitoring around neutral pH, although many fermentation processes are performed at pH < 6 on industrial scale. Thus, two new prototype acidic fluorescence pH sensors immobilized in single-use stirred-tank bioreactors, one with excitation at 470 nm and emission at 550 nm (sensor 470/550) and the other with excitation at 505 nm and emission at 600 nm (sensor 505/600), were characterized with respect to dynamic ranges and operational stability in representative fermentation media. Best resolution and dynamic range was observed with pH sensor 505/600 in mineral medium (dynamic range of 3.9 < pH < 7.2). Applying the same pH sensors to complex medium results in a drastic reduction of resolution and dynamic ranges. Yeast extract in complex medium was found to cause background fluorescence at the sensors’ operating wavelength combinations. Optical isolation of the sensor by adding a black colored polymer layer above the sensor spot and fixing an aperture made of adhesive photoresistant foil between the fluorescence reader and the transparent bottom of the polystyrene reactors enabled full re-establishment of the sensor’s characteristics. Reliability and operational stability of sensor 505/600 was shown by online pH monitoring (4.5 < pH < 5.8) of parallel anaerobic batch fermentations of Clostridium acetobutylicum for the production of acetone, butanol and ethanol (ABE) with offline pH measurements with a standard glass electrode as reference. © 2015 Springer-Verlag Berlin Heidelberg Source

Schneider K.,Saarland University | Schu tz V.,Saarland University | John G.T.,PreSens Precision Sensing GmbH | Heinzle E.,Saarland University
Bioprocess and Biosystems Engineering

We describe a new device with parallel optical measurement of dissolved oxygen (DO) and pH in up to nine shake flasks applicable in any conventional shaking incubator. Measurement ranges are 0-500% of air saturation for oxygen and 5.5-8.5 for pH. It was used to characterize growth profiles of different L-lysine producing strains of Corynebacterium glutamicum, of Saccharomyces cerevisiae and of Escherichia coli. Cultures in unbaffled flasks were highly reproducible. Oxygen limitation was indicated online which is particularly important when cultivating fast growing cells as E. coli. C. glutamicum strains showed distinct characteristic patterns of DO and pH indicating biological events. During the cultivation of S. cerevisiae on glucose, fructose and galactose, oxygen uptake rate was determined using the predetermined value of kLa. pH measurement was used to determine the minimum buffer requirement for a culture of C. glutamicum. © Springer-Verlag 2009. Source

Ries C.,ZHAW Zurich University of Applied Sciences | John G.,PreSens Precision Sensing GmbH | John C.,Redbiotec | Eibl R.,ZHAW Zurich University of Applied Sciences | Eibl D.,ZHAW Zurich University of Applied Sciences
Engineering in Life Sciences

While wave-mixed and stirred bag bioreactors are common devices for rapid, safe insect cell culture-based production at liter-scale, orbitally shaken disposable flasks are mainly used for screening studies at milliliter-scale. In contrast to the two aforementioned bag bioreactor types, which can be operated with standard or disposable sensors, shaker flasks have not been instrumented until recently. The combination of 250mL disposable shake flasks with PreSens's Shake Flask Reader enables both pH and dissolved oxygen to be measured, as well as allowing characterization of oxygen mass transfer. Volumetric oxygen transfer coefficients (k La-values) for PreSens 250mL disposable shake flasks, which were determined for the first time in insect cell culture medium at varying culture volumes and shaker frequencies, ranged between 4.4 and 37.9/h. Moreover, it was demonstrated that online monitoring of dissolved oxygen in shake flasks is relevant for limitation-free growth of insect cells up to high cell densities in batch mode (1.6×10 7 cells/mL) and for the efficient expression of an intracellular model protein. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA. Source

Santoro R.,University of Basel | Krause C.,PreSens Precision Sensing GmbH | Martin I.,University of Basel | Wendt D.,University of Basel
Journal of Tissue Engineering and Regenerative Medicine

Regulatory guidelines have established the importance of introducing quantitative quality controls during the production and/or at the time of release of cellular grafts for clinical applications. In this study we aimed to determine whether on-line measurements of oxygen can be used as a non-destructive method to estimate the number of chondrocytes within an engineered cartilage graft. Human chondrocytes were seeded and cultured in a perfusion bioreactor, and oxygen levels in the culture medium were continuously monitored at the inlet and outlet of the bioreactor chamber throughout the culture period. We found that the drop in oxygen across the perfused construct was linearly correlated with the number of cells per construct (R 2=0.82, p<0.0001). The method was valid for a wide range of cell numbers, including cell densities currently used in the manufacture of cartilage grafts for clinical applications. Given that few or no non-destructive assays that quantitatively characterize an engineered construct currently exist, this non-invasive method could represent a relevant instrument in regulatory compliant manufacturing of engineered grafts meeting specific quality criteria. © 2012 John Wiley & Sons, Ltd. Source

A sensor assembly, a method, and a measuring system for capturing the distribution of at least one variable of an object are disclosed. The sensor assembly has at least one sensor element comprising at least one first sensor sub-element and at least one second sensor sub-element. The at least one first sensor sub-element is transparent for at least one wavelength region of light, the at least one second sensor sub-element is sensitive to at least one variable. Furthermore a method and measuring system and an illumination system for illuminating the sensor assembly and the object is provided.

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