Non-contact Raman spectroscopy for in-line monitoring of glucose and ethanol during yeast fermentations
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The monitoring of microbiological processes using Raman spectroscopy has gained in importance over the past few years. Commercial Raman spectroscopic equipment consists of a laser, spectrometer, and fiberoptic immersion probe in direct contact with the fermentation medium. To avoid possible sterilization problems and biofilm formation on the probe tip, a large-aperture Raman probe was developed. The design of the probe enables non-contact in-line measurements through glass vessels or inspection glasses of bioreactors and chemical reactors. The practical applicability of the probe was tested during yeast fermentations by monitoring the consumption of substrate glucose and the formation of ethanol as the product. Multiple linear regression models were applied to evaluate the Raman spectra. Reference values were determined by high-performance liquid chromatography. The relative errors of prediction for glucose and ethanol were 5 and 3%, respectively. The presented Raman probe allows simple adaption to a wide range of processes in the chemical, pharmaceutical, and biotechnological industries.
KeywordsNon-contact Raman spectroscopy In-line reaction monitoring Multiple linear regression Saccharomyces cerevisiae Glucose and ethanol
We gratefully acknowledge the support from the Albert and Anneliese Konanz-Foundation of the Mannheim University of Applied Sciences. We would also like to thank the Institute for Technical Microbiology (Mannheim University of Applied Sciences, Germany), especially Kerstin Schlosser, for providing the HPLC system. Furthermore, the authors would like to thank Dr. Hanns Simon Eckhardt (tec5 AG, Germany) for technical support. This work was funded by the German Federation of Industrial Research Associations (AiF Project GmbH, Funding Code 2035756LW3).
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Conflict of interest
The authors declare no financial or commercial conflict of interest.
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