1 Department of Chemical and Biochemical Engineering, Technical University of Denmark2 Center for Process Engineering and Technology, Department of Chemical and Biochemical Engineering, Technical University of Denmark3 Department of Photonics Engineering, Technical University of Denmark
Existing methods for pH control in bench-scale bioreactor systems often cannot be directly adapted for microbioreactors. This is because microbioreactors are commonly designed to work with constant volumes, operate bubble-free and have no headspace, which technically rules out any possibility of adding acid/base solution for pH control in microbioreactors. This work reports on the establishment of a gaseous pH control concept in microbioreactors where pH control was achieved by dosing of ammonia (NH3, 20 000 ppm) and pure carbon dioxide (CO2) gases to respectively; increase and lower the pH of the reactor content. It encompasses the establishment of an optical pH measurement by means of a fluorescent sensor spot, realization of the necessary gas connections, mixing of gases, and gas-exchange via a thin semi-permeable poly(dimethylsiloxane) (PDMS) membrane. It was shown that addition of NH3 and CO2 gases coupled to a simple on/off controller results in a satisfactorily control performance (pH control accuracy = + 0.1 of the set point value and system responses of a few minutes were achieved) within the dynamic measuring range of the optical sensor spot which is between pH 6 and 8.
Proceedings of 2012 3rd International Conference on Food Engineering and Biotechnology, 2012