On-line carbon balance of yeast fermentations using miniaturized optical sensors

• Published in: Journal of bioscience and bioengineering Vol. 113; no. 3; pp. 399 - 405
• Main Authors: Beuermann, Thomas, Egly, Dominik, Geoerg, Daniel, Klug, Kerris Isolde, Storhas, Winfried, Methner, Frank-Juergen
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2012; Elsevier
• Subjects: aeration; Biological and medical sciences; Biomass; Bioreactors; Biotechnology; Calibration; carbon; Carbon - metabolism; Carbon balance; carbon dioxide; Cell Count; culture media; ethanol; Ethanol - metabolism; Ethanol determination; Fermentation; Fiber Optic Technology; fiber optics; Fundamental and applied biological sciences. Psychology; Glucose - metabolism; Industrial Microbiology - instrumentation; metabolites; Methods. Procedures. Technologies; Microbial engineering. Fermentation and microbial culture technology; mixing; monitoring; On-line process monitoring; Online Systems; Optical Fibers; Optical sensors; prices; Saccharomyces cerevisiae - metabolism; spectrometers; temperature; vapors; Yeast fermentation; Yeasts; Yeast fermentation; Ethanol determination; On-line process monitoring; Optical sensors; Carbon balance; On line; Yeast; Ethanol; Optical sensor; Fermentation; Miniaturization; Operating process; Monitoring
• ISSN: 1389-1723; 1347-4421
• DOI: 10.1016/j.jbiosc.2011.10.016

Monitoring of microbiological processes using optical sensors and spectrometers has gained in importance over the past few years due to its advantage in enabling non-invasive on-line analysis. Near-infrared (NIR) and mid-infrared (MIR) spectrometer set-ups in combination with multivariate calibrations have already been successfully employed for the simultaneous determination of different metabolites in microbiological processes. Photometric sensors, in addition to their low price compared to spectrometer set-ups, have the advantage of being compact and are easy to calibrate and operate. In this work, the detection of ethanol and CO2 in the exhaust gas during aerobic yeast fermentation was performed by two photometric gas analyzers, and dry yeast biomass was monitored using a fiber optic backscatter set-up. The optical sensors could be easily fitted to the bioreactor and exhibited high robustness during measuring. The ethanol content of the fermentation broth was monitored on-line by measuring the ethanol concentration in the fermentation exhaust and applying a conversion factor. The vapor/liquid equilibrium and the associated conversion factor strongly depend on the process parameter temperature but not on aeration and stirring rate. Dry yeast biomass was determined in-line by a backscattering signal applying a linear calibration. An on-line balance with a recovery rate of 95–97% for carbon was achieved with the use of three optical sensors (two infrared gas analyzers and one fiber optic backscatter set-up).