Chemical Engineering Science, Vol.50, No.16, 2601-2610, 1995
Acoustic Off-Gas Analyzer for Bioreactors - Precision, Accuracy and Dynamics of Detection
This pager reports on the performance of a compact, acoustic gas analyser for the measurement of oxygen and carbon dioxide in the exhaust gas from aerated bioreactors. Characterization of the analyser in terms of its precision, accuracy, response time, and signal drift shows that its performance is comparable to that of a good mass-spectrometer. Interference by water vapour on the performance of the acoustic carbon dioxide measurement is discussed. A simple way of avoiding this source of interference is to pass the exhaust gas through a Nafion(R) tube before it enters the analyser. This method results in near-complete removal of water vapour from the exhaust gas. Relating transient responses in the exhaust gas composition to the metabolism of the microorganism is often hampered by the dynamics of physical and chemical processes within the bioreactor. The importance of signal noise generated by these physical/chemical processes is discussed based on a time constant analysis of fermentation processes with yeast and filamentous fungi. Finally, the precision and stability of the detector is demonstrated by measurements on an aerobic, oscillating continuous culture of Saccharomyces cerevisiae.