title: Rapid profiling of antimicrobial compounds characterising B. subtilis TR50 cell-free filtrate by high-performance liquid chromatography coupled to high-resolution Orbitrap™ mass spectrometry.
abstract: BACKGROUND
  Several Bacillus strains, typically isolated from different food sources, represent renowned producers of a multitude of low and high molecular weight compounds, including lipopeptides and macrolactones, with an importance for their antimicrobial activity. The high homology shared by many of these compounds also occurring as closely related isoforms poses a challenge in their prompt detection.
  
  
  METHODS
  Identification and structural elucidation is generally achieved by matrix-assisted laser desorption/ionization (MALDI) or liquid chromatography (LC) coupled to mass spectrometry (MS) after a pre-fractionation and/or purification step of the extract. In this paper we report the application of a method based on LC separation and high-resolution Orbitrap™-based MS for the rapid screening of raw filtrate of the strain Bacillus subtilis TR50 endowed with antimicrobial activity, without requiring any sample pre-treatment.
  
  
  RESULTS
  Upon direct analysis of the cell-free filtrate of Bacillus subtilis TR50 by high-resolution mass spectrometry (HRMS), different compounds families, that proved to exert a remarked antimicrobial activity against several foodborne pathogens, can be readily displayed along the chromatographic run. Among them, three different classes were identified and characterized belonging to the iturin, fengycin and surfactin groups. The high resolving power and accurate mass accuracy provided by the HRMS system in use ensured an enhanced selectivity compared to other mass spectrometers. In addition, after activation of the HCD cell, the HR-MS/MS spectra can provide insights in the structural elucidation of several compounds.
  
  
  CONCLUSIONS
  The acquisition of HRMS spectra of raw filtrates of subtilis strains allows untargeted analysis of the major classes of compounds produced to be performed, thus facilitating identification of other unknown bioactive molecules after retrospective analysis. These features make this approach a fast tool applicable to the rapid screening and further identification of antimicrobial compounds released by Bacillus strains in raw filtrates.
authors.affiliation: Institute of Sciences of Food Production, National Research Council of Italy (ISPA-CNR), Via Amendola 122/O, 70126, Bari, Italy.
authors.forename: Linda
authors.initials: L
authors.lastname: Monaci
authors.affiliation: Institute of Sciences of Food Production, National Research Council of Italy (ISPA-CNR), Via Amendola 122/O, 70126, Bari, Italy.
authors.forename: Laura
authors.initials: L
authors.lastname: Quintieri
authors.affiliation: Institute of Sciences of Food Production, National Research Council of Italy (ISPA-CNR), Via Amendola 122/O, 70126, Bari, Italy.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Caputo
authors.affiliation: Institute of Sciences of Food Production, National Research Council of Italy (ISPA-CNR), Via Amendola 122/O, 70126, Bari, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Visconti
authors.affiliation: Institute of Sciences of Food Production, National Research Council of Italy (ISPA-CNR), Via Amendola 122/O, 70126, Bari, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Baruzzi
mesh_terms: D000890:Anti-Infective Agents / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification; D001412:Bacillus subtilis / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D005374:Filtration; D055666:Lipopeptides; D010456:Peptides, Cyclic; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000890:Anti-Infective Agents; D055666:Lipopeptides; D010456:Peptides, Cyclic; C049972:fengycin; C009365:surfactin peptide