title: Metabolic fingerprinting of Lactobacillus paracasei: a multi-criteria evaluation of methods for extraction of intracellular metabolites.
abstract: An untargeted multi-criteria approach was used to select the best extraction method among freeze-thawing in methanol (FTM), boiling ethanol (BE) and chloroform-methanol (CM) for gas chromatography mass spectrometry (GC-MS) metabolic fingerprinting of Lactobacillus paracasei subsp. paracasei (CRL-431®). The following results were obtained: (i) coverage and efficiency, measured by the number of features extracted and the sum of feature intensities, showed that FTM extraction resulted in the largest compound coverage with a total number of features 8.9 × 10(3) ± 0.5 × 10(3), while merely 6.6 × 10(3) ± 0.9 × 10(3) and 7.9 × 10(3) ± 0.8 × 10(3) were detected in BE or CM, respectively; (ii) the similarity of extraction methods, measured by common features, demonstrated that FTM yielded the most complementary information to BE and CM; i.e. 17 and 33 % of the features of FTM extracted were unique compared to CM and BE, respectively; and (iii) a clear-cut separation according to extraction method was demonstrated by assessment of the metabolic fingerprints by pixel-based data analysis. Indications of metabolite degradation were observed under the elevated temperature for BE extraction. A superior coverage of FTM together with a high repeatability over nearly the whole range of GC-amenable compounds makes this the extraction method of choice for metabolic fingerprinting of L. paracasei.
authors.affiliation: Analytical Chemistry Group, Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark, dkkba@chr-hansen.com.
authors.forename: Kristina B
authors.initials: KB
authors.lastname: Jäpelt
authors.forename: Nikoline J
authors.initials: NJ
authors.lastname: Nielsen
authors.forename: Stefanie
authors.initials: S
authors.lastname: Wiese
authors.forename: Jan H
authors.initials: JH
authors.lastname: Christensen
mesh_terms: D002725:Chloroform / Q000737:chemistry; D005615:Freezing; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D007778:Lactobacillus / Q000737:chemistry / Q000378:metabolism*; D055442:Metabolome; D055432:Metabolomics / Q000379:methods*; D000432:Methanol / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D044366:Transition Temperature
chemical_list: D012997:Solvents; D002725:Chloroform; D000432:Methanol