Detection of Microorganisms with an Electronic Nose for Application under Microgravity Conditions

Abstract

<jats:title>Abstract</jats:title><jats:p>In this work, we report on the construction, training and functional assessment of an electronic nose (called ‘E-Nose’) that is capable of monitoring the microbial contamination onboard space ships under microgravity conditions. To this end, a commercial electronic nose was modified to allow for the sampling of microbial volatile organic compounds (MVOCs) emitted from relevant bacterial and fungi species. Training of the modified ‘E-Nose’ was performed by establishing an MVOC database consisting of two Gram-positive bacteria strains (Bacillus subtilis and Staphylococcus warneri) and two fungi strains (Aspergillus versicolor and Penicillium expansum). All these strains are known to exist onboard the International Space Station (ISS) and to form important parts of its microbial contamination. All cultures were grown on four kinds of structural materials also in use onboard the ISS. The MVOCs emitted during the different growth phases of these cultures were monitored with an array of ten different metal oxide gas sensors inside the ‘E-Nose’. Principal component analysis of the array data revealed that B. subtilis and S. warneri form separate clusters in an optimized score plot, while the two fungi strains of A. versicolor and P. expansum form a large common cluster, well discriminated against to the bacteria clusters.</jats:p>

Electronic Nose for Differentiation and Quantification of Yeast Species in White Fresh Soft Cheese

“…It is based on detecting volatile organic compounds (VOCs). It has been successfully used in several biological and agricultural applications [11,12], especially in food spoilage [13][14][15][16][17][18]. Furthermore, it was used for the identification of several bacterial strains and fungi strains, since these microorganisms can produce VOCs during their metabolic activities.…”

Supporting wound infection diagnosis: advancements and challenges with electronic noses

“…This allows to transferring identified VOC-fingerprints to learn for other strains of the species (Kunze et al, 2013). It was further found that also the composition of the produced volatiles stays constant during the exponential growth of the microorganisms although the emission of volatiles increases with the number of colony-forming units (CFU) (Reidt et al, 2020). It should critically be noted here that not all studies distinguished precisely between colonization and wound infection.…”

“…However, MOS sensors are known to have weak precision, are susceptible to poisoning and sensitive to humidity (Karakaya et al, 2020). While the influence of humidity on the sensor performance can be decreased by integration of an independent humidity sensor (Reidt et al, 2020), well-known drift issues and lacking long-term stability still decrease sensor´s ability to provide stable signals over a sufficiently long period (Chai et al, 2022). Such a long-term stability is, however, crucial for long-term data collection to monitor wounds.…”

Self-Adaptation of Oxygen Adsorption and Sub-Surface Junction Formation in Thin Nanometric Sheets of Metal Oxides

“…Metal oxide (MOX) gas sensors and sensor arrays, i.e., E-Noses [1], are widely employed in the detection of gases and gas concentrations in the ambient air to aid in a multitude of safety, security, medical, automotive and industrial control scenarios [2][3][4][5][6][7][8][9][10][11][12][13]. All of these applications have been enabled by making progress along the three main directions of research, namely by striving for higher sensitivity, selectivity and stability [14].…”