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Shapaval V.,Noflma Materials AS | Shapaval V.,Norwegian University of Life Sciences | Walczak B.,University of Silesia | Gognies S.,British Petroleum | And 6 more authors.
Analyst | Year: 2013

The application of Fourier Transform Infrared Spectroscopy for characterization of yeasts is growing rapidly. Since it is known that the phenotypic expression of yeast cells depends sensitively on the nutrients that are available in the growth medium, one standardized growth medium is usually used for identification and characterization purposes in order to obtain reproducible FTIR signals. Since our recently developed high-throughput micro-cultivation protocol has the capacity to use more than one standardized growth medium, we wanted to investigate if the parallel use of multiple growth media can improve identification results. For this purpose, five different cultivation media (YP, YPD, YMB, SAB and SD) were used. In total 91 food spoilage yeast strains of 12 different genera were cultivated in different cultivation media and subsequently characterized by FTIR spectroscopy. For spectral identifications, Radial Basis Function-Partial Least Squares (RBF-PLS) was used in combination with cross-model validation where an inner cross-validation loop was used to optimize the model, while in an outer loop an independent test set was kept aside to test the optimized model. Sensitivity and specificity were evaluated for each studied genus class. The results show that the YMB selective medium gave the best discrimination results for 9 of the 12 genera with sensitivity above 90%. Only three genera showed better identification results on other media (Clavispora and Metschnikowia on medium SD, Debaryomyces on medium YPD). We therefore suggest to use the media SD, YPD in combination with the YMB medium for the identification of food spoilage yeasts. © The Royal Society of Chemistry 2013. Source


Habimana O.,Noflma Materials AS | Heir E.,Noflma Materials AS | Langsrud S.,Noflma Materials AS | Asli A.W.,Noflma Materials AS | Moretro T.,Noflma Materials AS
Applied and Environmental Microbiology | Year: 2010

A meat factory commensal bacterium, Acinetobacter calcoaceticus, affected the spatial distribution of Escherichia coli 0157:H7 surface colonization. The biovolume of E. coli 0157:H7 was 400-fold higher (1.2 × 106 μm3) in a dynamic cocultured biofilm than in a monoculture (3.0 × 103 μm3), and E. coli O157:H7 colonized spaces between A. calcoaceticus cell clusters. Copyright © 2010, American Society for Microbiology. All Rights Reserved. Source

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