Journal: International Journal of Food Microbiology

Abbreviation

Int. j. food microbiol.

Publisher

Elsevier

Journal Volumes

ISSN

0168-1605
1879-3460

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Publications 1 - 10 of 25
  • Facultative anaerobic halophilic and alkaliphilic bacteria isolated from a natural smear ecosystem inhibit Listeria growth in early ripening stages
    Item type: Journal Article
    Roth, Emmanuelle; Schwenninger, Susanne Miescher; Eugster-Meier, Elisabeth; et al. (2011)
    International Journal of Food Microbiology
  • Molecular structure and evolution of the conjugative multiresistance plasmid pRE25 of Enterococcus faecalis isolated from a raw-fermented sausage
    Item type: Conference Proceedings
    Teuber, Michael; Schwarz, Franziska; Perreten, Vincent (2003)
    International Journal of Food Microbiology
  • Screening of lactic acid bacteria and yeast strains to select adapted anti-fungal co-cultures for cocoa bean fermentation
    Item type: Journal Article
    Romanens, Edwina; Freimüller Leischtfeld, Susette; Volland, Andrea; et al. (2019)
    International Journal of Food Microbiology
  • Post-high-pressure temperature and time — Overlooked parameters in high pressure treatment of bacterial spores
    Item type: Journal Article
    Heydenreich, Rosa; Delbrück, Alessia I.; Mathys, Alexander (2023)
    International Journal of Food Microbiology
    High pressure (HP) processing has high potential for bacterial spore inactivation with minimal thermal input. To advance HP germination and subsequent inactivation of spores, this study explored the physiological state of HP-treated spores using flow cytometry (FCM). Bacillus subtilis spores were treated at 550 MPa and 60 °C (very HP (vHP)) in buffer, incubated after the HP treatment, and stained for FCM analysis with SYTO16 indicating germination and propidium iodide (PI) indicating membrane damage. FCM subpopulations were analyzed depending on the HP dwell time (≤20 min), post-HP temperature (ice, 37 °C, 60 °C) and time (≤4 h), germination-relevant cortex-lytic enzymes (CLEs) and small-acid-soluble-proteins-(SASP)-degrading enzymes by using deletion strains. The effect of post-HP temperatures (ice, 37 °C) was additionally studied for moderate HP (150 MPa, 38 °C, 10 min). Post-HP incubation conditions strongly influenced the prevalence of five observed FCM subpopulations. Post-HP incubation on ice did not or only slowly shifted SYTO16-positive spores to higher SYTO16 levels. At 37 °C post-HP, this shift accelerated, and a shift to high PI intensities occurred depending on the HP dwell time. At 60 °C post-HP, the main shift was from SYTO16-positive to PI-positive subpopulations. The enzymes CwlJ and SleB, which are CLEs, seemed both necessary for PI or SYTO16 uptake, and to have different sensitivities to 550 MPa and 60 °C. Different extents of SASP degradation might explain the existence of two SYTO16-positive subpopulations. Shifts to higher SYTO16 intensities during post-HP incubation on ice or at 37 °C might rely on the activity and recovery of CLEs, SASP-degrading enzymes or their associated proteins from reversible HP-induced structural changes. These enzymes seemingly become active only during decompression or after vHP treatments (550 MPa, 60 °C). Based on our results, we provide a refined model of HP germination-inactivation of B. subtilis spores and an optimized FCM method for quantification of the safety-relevant subpopulation, i.e., vHP (550 MPa, 60 °C) superdormant spores. This study contributes to the development of mild spore inactivation processes by shedding light on overlooked parameters: post-HP incubation conditions. Post-HP conditions significantly influenced the physiological state of spores, likely due to varying enzymatic activity. This finding may explain inconsistencies in previous research and shows the importance of reporting post-HP conditions in future research. Furthermore, the addition of post-HP conditions as HP process parameter may open up new possibilities to optimize HP-based inactivation of spores for potential industrial applications in the food industry.
  • Exopolysaccharides from co-cultures of Weissella confusa 11GU-1 and Propionibacterium freudenreichii JS15 act synergistically on wheat dough and bread texture
    Item type: Journal Article
    Tinzl-Malang, Saskia K.; Rast, Peter; Grattepanche, Franck; et al. (2015)
    International Journal of Food Microbiology
  • Enterobacter sakazakii bacteriophages can prevent bacterial growth in reconstituted infant formula
    Item type: Journal Article
    Kim, Kwang-Pyo; Klumpp, Jochen; Loessner, Martin J. (2007)
    International Journal of Food Microbiology
  • Characterization of high-pressure-treated Bacillus subtilis spore populations using flow cytometry – Shedding light on spore superdormancy at 550 MPa
    Item type: Journal Article
    Heydenreich, Rosa; Delbrück, Alessia I.; Peternell, Christina; et al. (2024)
    International Journal of Food Microbiology
    Mild spore inactivation can be challenging in industry because of the remarkable resistance of bacterial spores. High pressure (HP) can trigger spore germination, which reduces the spore's resistance, and thereby allows mild spore inactivation. However, spore germination is heterogenous. Some slowly germinating or non-germinating spores called superdormant spores remain resistant and can survive. Therefore, superdormant spores need to be characterized to understand the causes of their germination deficiency. Bacillus subtilis spores were pressurized for 50 s–6 min at a very high pressure (vHP) level of 550 MPa and 60 °C in buffer to trigger germination. For a rapid quantification of the remaining ungerminated superdormant spores, flow cytometry (FCM) analysis was validated using single cell sorting and growth analysis. FCM based on propidium iodide (PI) and SYTO16 can be used for 550 MPa-superdormant spores after short vHP treatments of ≤1 min and post-HP incubation at 37 °C or 60 °C. The need for a post-HP incubation is particular for vHP treatments. The incubation was successful to separate FCM signals from superdormant and germinated spores, thus allowing superdormant spore quantification. The SYTO16 and PI fluorescence levels did not necessarily indicate superdormancy or apparent viability. This highlights the general need for FCM validation for different HP treatment conditions. The ~7 % of ungerminated, i.e., superdormant, spores were isolated after a vHP treatment (550 MPa, 60 °C, 43–52 s). This allowed the characterization of vHP superdormant spores for the first time. The superdormant spores had a similar dipicolinic acid content as spores of the initial dormant population. Descendants of superdormant spores had a normal vHP germination capacity. The causes of vHP superdormancy were thus unlikely linked to the dipicolinic acid content or a permanent genetic change. Isolated superdormant spores germinated better in a second vHP treatment compared to the initial spore population. This has not been observed for other germination stimuli so far. In addition, the germination capacity of the initial spore population was time-dependent. A vHP germination deficiency can therefore be lost over time and seems to be caused by transient factors. Permanent cellular properties played a minor role as causes of superdormancy under chosen HP treatment conditions. The study gained new fundamental insights in vHP superdormancy which are of applied interest. Understanding superdormancy helps to efficiently develop a strategy to avoid superdormant spores and hence to inactivate all spores. The development of a mild HP spore germination-inactivation process aims at better preserving the food quality.
  • Biocontrol of Salmonella Typhimurium in RTE foods with the virulent bacteriophage FO1-E2
    Item type: Journal Article
    Guenther, Susanne; Herzig, Oliver; Fieseler, Lars; et al. (2012)
    International Journal of Food Microbiology
  • In situ enrichment of folate by microorganisms in beta-glucan rich oat and barley matrices
    Item type: Journal Article
    Kariluoto, Susanna; Edelmann, Minnamari; Nyström, Laura; et al. (2014)
    International Journal of Food Microbiology
  • Prevalence and comparison of Streptococcus infantarius subsp. infantarius and Streptococcus gallolyticus subsp. macedonicus in raw and fermented dairy products from East and West Africa
    Item type: Journal Article
    Jans, Christoph; Kaindi, Dasel Wambua Mulwa; Böck, Désirée; et al. (2013)
    International Journal of Food Microbiology
Publications 1 - 10 of 25