On-Line Monitoring of Microbial Volatile Metabolites by Proton Transfer Reaction-Mass Spectrometry

This study presents a method for the on-line analysis of volatile organic compounds (VOCs) from microbial cultures using proton transfer reaction-mass spectrometry (PTR-MS). The objective was to establish a sampling system capable of real-time monitoring of VOCs within the dynamic headspaces of microbial cultures. The methodology involved evaluating the novel PTR-MS technique with four reference organisms: Escherichia coli, Shigella flexneri, Salmonella enterica, and Candida tropicalis. By analyzing headspace VOCs from both actively growing cultures and uninoculated controls, distinctive marker ions were identified for each microbial culture. Notably, C. tropicalis exhibited several unique markers, while E. coli and S. enterica were discernible from each other and S. flexneri through specific marker ions, underscoring the method's potential to differentiate closely related microorganisms. Moreover, while some VOC temporal profiles correlated with microbial growth dynamics, most demonstrated distinct patterns, highlighting the significance of understanding VOC emission evolution during growth for accurate characterization. This research contributes to the establishment of on-line PTR-MS analysis as a routine tool for monitoring environmentally relevant and biotechnological processes.