title: In situ investigation of Geobacillus stearothermophilus spore germination and inactivation mechanisms under moderate high pressure.
abstract: Bacterial spores are a major concern for food safety due to their high resistance to conventional preservation hurdles. Innovative hurdles can trigger bacterial spore germination or inactivate them. In this work, Geobacillus stearothermophilus spore high pressure (HP) germination and inactivation mechanisms were investigated by in situ infrared spectroscopy (FT-IR) and fluorometry. G. stearothermophilus spores' inner membrane (IM) was stained with Laurdan fluorescent dye. Time-dependent FT-IR and fluorescence spectra were recorded in situ under pressure at different temperatures. The Laurdan spectrum is affected by the lipid packing and level of hydration, and provided information on the IM state through the Laurdan generalized polarization. Changes in the -CH2 and -CH3 asymmetric stretching bands, characteristic of lipids, and in the amide I' band region, characteristic of proteins' secondary structure elements, enabled evaluation of the impact of HP on endospores lipid and protein structures. These studies were complemented by ex situ analyses (plate counts and microscopy). The methods applied showed high potential to identify germination mechanisms, particularly associated to the IM. Germination up to 3 log10 was achieved at 200 MPa and 55 °C. A molecular-level understanding of these mechanisms is important for the development and validation of multi-hurdle approaches to achieve commercial sterility.
authors.affiliation: German Institute of Food Technologies (DIL), Prof.-von-Klitzing-Str. 7, 49610 Quakenbrück, Germany. Electronic address: e.georget@dil-ev.de.
authors.forename: Erika
authors.initials: E
authors.lastname: Georget
authors.affiliation: Technische Universität Dortmund, Biophysikalische Chemie, Fakultät für Chemie und Chemische Biologie, Otto-Hahn Str. 6, 44227 Dortmund, Germany.
authors.forename: Shobhna
authors.initials: S
authors.lastname: Kapoor
authors.affiliation: Technische Universität Dortmund, Biophysikalische Chemie, Fakultät für Chemie und Chemische Biologie, Otto-Hahn Str. 6, 44227 Dortmund, Germany.
authors.forename: Roland
authors.initials: R
authors.lastname: Winter
authors.affiliation: Leibniz Institute for Agricultural Engineering Potsdam-Bornim e.V., Max-Eyth-Allee 100, 14469 Potsdam, Germany.
authors.forename: Kai
authors.initials: K
authors.lastname: Reineke
authors.affiliation: German Institute of Food Technologies (DIL), Prof.-von-Klitzing-Str. 7, 49610 Quakenbrück, Germany.
authors.forename: Youye
authors.initials: Y
authors.lastname: Song
authors.affiliation: Nestlé Research Center, Route du Jorat 57, Vers-Chez-Les-Blanc, 1000 Lausanne, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Callanan
authors.affiliation: Nestlé Research Center, Route du Jorat 57, Vers-Chez-Les-Blanc, 1000 Lausanne, Switzerland.
authors.forename: Edwin
authors.initials: E
authors.lastname: Ananta
authors.affiliation: German Institute of Food Technologies (DIL), Prof.-von-Klitzing-Str. 7, 49610 Quakenbrück, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Heinz
authors.affiliation: German Institute of Food Technologies (DIL), Prof.-von-Klitzing-Str. 7, 49610 Quakenbrück, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Mathys
mesh_terms: D001411:Geobacillus stearothermophilus / Q000737:chemistry* / Q000254:growth & development; D006358:Hot Temperature; D050296:Microbial Viability; D011312:Pressure; D013171:Spores, Bacterial / Q000737:chemistry / Q000254:growth & development*; D013242:Sterilization / Q000379:methods*
keywords: Bacterial spore; FT-IR spectroscopy; Fluorescence; Germination; High pressure; In situ