Bioreactor contamination monitoring using off-gassed volatile organic compounds (VOCs)

Metabolically active cells emit volatile organic compounds (VOCs) that can be used in real time to non-invasively monitor the health of cell cultures. We utilized these naturally occurring VOCs in an adapted culture method to detect differences in culturing Chinese hamster ovary (CHO) cells with and without Staphylococcus epidermidis and Aspergillus fumigatus contaminations. The VOC emissions from the cell cultures were extracted and measured from the culture flask headspace using polydimethylsiloxane (PDMS)-coated Twisters, which were subjected to thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) analysis. In our initial time points of 1 and 2 h, we detected VOC signatures that differentiated the cultures earlier than traditional plating techniques or visualization methods. Partial least squares-discriminant analysis (PLS-DA) models were built to differentiate the analytes from the CHO cells and S. epidermidis- and A. fumigatus-inoculated CHO cultures. A total of 41 compounds with a variable importance in projection (VIP) score greater than 1 was obtained across the models. Similarly, based on the PLS regression analyses to predict the cell concentration of S. epidermidis (R² = 0.891) and A. fumigatus (R² = 0.375), 15 and 20 relevant compounds were putatively identified, respectively; two known compounds overlapped between the two microbes. Some of the compounds were unidentified and future studies will determine the relationship between the VOCs and the metabolic changes in contaminated cultures.