Are bacterial spores activated by High Pressure treatment at 20°C ?

2019

International audience

Effect of high pressure on the antimicrobial activity and secondary structure of the bacteriocin nisin

2018

International audience; Effect of high pressure (HP) treatment on the antimicrobial properties and the structure of nisin was evaluated. Nisin solutions at pH 2.8 or 6.1 were treated by HP at 500 MPa – 10 min – 20 °C and their antimicrobial potency was determined. It appeared that HP clearly impacted the antimicrobial activity of nisin, with respective activity loss of 22.5% and 49.9% at pH 2.8 and 6.1. Structural analysis of nisin by circular dichroism and Fourier transform-infrared spectroscopies revealed that the decrease of nisin antimicrobial activity was likely due to the unfolding of the protein induced by HP. A loss of nisin β-turns structure, particularly significant at neutral pH,…

Viscosity mapping of the structures of Bacillus subtilis spores by fluorescence lifetime imaging

2015

International audience; L’état de la membrane plasmique des cellules est un élément essentiel pour connaitre la conditionphysiologique des cellules. Sur des microorganismes, cette connaissance permet de mesurer l’impact d’uneperturbation sur la structure cellulaire et sur sa survie ultérieure. La fluidité membranaire résulte tout à lafois de la composition en phospholipides, de la présence et du rôle de certaines molécules comme lesstérols, les protéines transmembranaires mais aussi des conditions thermodynamiques et physico-chimiquesextérieures (P, T, aw). La bactérie Bacillus subtilis est capable dans des conditions défavorables de passerd’un état actif végétatif à l’état de spore, état d…

Assessment of Salmonella and Listeria monocytogenes level in ready-to-cook poultry meat: Effect of various high pressure treatments and potassium lac…

2014

International audience; The objective of this study was to develop a probabilistic model in order to determine the contamination level of Salmonella and Listeria monocytogenes in ready-to-cook poultry meat, after a high pressure (HP) treatment. The model included four steps: i) Reception of raw meat materials, mincing and mixing meat, ii) Partitioning and packaging into 200-g modified atmosphere packs, iii) High pressure treatment of the meat, and iv) Storage in chilled conditions until the end of the shelf-life. The model excluded the cooking step and consumption at consumer's home as cooking practices and heating times are highly variable. The initial contamination level of Salmonella and…

Effect of Combined Physical Stresses on Cells: The Role of Water

2010

International audience; The role of water in microorganism viability was assessed through the application of combined physical perturbations. The combination of different physical parameters could allow to balance the properties variations (especially water related) resulting from the increase of one parameter alone. Thus, it is possible to optimize the survival of cells in controlling these parameters. This was tested through two different examples. The first example shows that combination of osmotic level and temperature can allow optimizing yeast cell survival in following membrane fluidity variation. Moreover this analysis has allowed a better comprehension of cell inactivation during r…

La biopréservation: une stratégie d’avenir pour la conservation des aliments

2015

N° d'article 201511121820; La demande grandissante des consommateurs pour des produits alimentaires à teneur réduite en conservateurs pousse les industriels de l’agroalimentaire à rechercher des méthodes de conservation alternatives. Dans ce contexte, la bioprotection s’impose comme un procédé à fort potentiel. Cette technique consiste à inoculer sur les aliments des cultures de bactéries protectrices. Celles-ci, par l’intermédiaire de plusieurs mécanismes, vont inhiber la croissance de bactéries pathogènes et d’altération telles que Listeria monocytogenes et Salmonella. Cependant, cette technique n’a pas d’effet sur les spores bactériennes. Ainsi, l’objet central du projet de recherche ANR…

Are bacterial spores activated by High Pressure treatment at 20°C ?

2018

Combined use of modified atmosphere packaging and high pressure to extend the shelf-life of raw poultry sausage

2014

International audience; The contribution of modified atmosphere packaging (MAP) in extending the shelf-life of high-pressure treated raw poultry sausages was examined by considering microbial and oxidative stability (TBARs) aspects. Raw poultry sausages packaged under air or modified atmosphere (50% CO2–50% N2) were pressurized at 500 MPa during 5 min at a maximum temperature of 10.5 °C, subsequently allowed to refrigerated storage during 22 days. During storage, samples were tested at time intervals for headspace gas composition, pH, TBARs, Aerobic Mesophilic Counts (AMC) and Lactic Acid Bacteria (LAB) counts. The high pressure treatment could represent an efficient means of extending the …

The role of water in bacteria spore resistance

2016

Understanding low hydration state of bacteria spores

2019

Cryopreservation of Escherichia coli K12TG1: Protection from the damaging effects of supercooling by freezing

2015

Injuries in living cells caused by water freezing during a freeze-thaw process have been extensively reported. In particular, intracellular water freezing has long been incriminated in cell death caused by a high cooling rate, but this supposition could not always be demonstrated. This work aims to discriminate the role of water freezing, dehydration and cold-induced injuries in cellular damage occuring during cryopreservation. For this purpose, Escherichia coli K12TG1 suspensions were maintained in a supercooled or frozen state at -20°C for times ranging from 10 min to 5 h. The supercooled state was maintained for a long period at -20°C by applying a non-injurious isostatic pressure (P<40 …

Environmentally eco-reasoned design process for functional yeast production and stabilization

2015

Environmentally eco-reasoned design process for functional yeast production and stabilization. 3. European Congress of Applied Biotechnology (ECAB 3)

Multi-criteria framework as an innovative tradeoff approach to determine the shelf-life of high pressure-treated poultry

2016

International audience; A multi-criteria framework combining safety, hygiene and sensorial quality was developed to investigate the possibility of extending the shelf-life and/or removing lactate by applying High Hydrostatic Pressure (HHP) in a ready-to-cook (RTC) poultry product. For this purpose, Salmonella and Listeria monocytogenes were considered as safety indicators and Escherichia coli as hygienic indicator. Predictive modeling was used to determine the influence of HHP and lactate concentration on microbial growth and survival of these indicators. To that end, probabilistic assessment exposure models developed in a previous study (Lerasle, M., Guillou, S., Simonin, H., Anthoine, V.,…

High pressure treatment at mild temperature induces irreversible sensitization of bacterial spores to antimicrobial agents

2016

Characterization of cryoprotectants ternary mixture according to cooling rates

2015

Understanding the Effects of High Pressure on Bacterial Spores Using Synchrotron Infrared Spectroscopy

2020

International audience; Bacterial spores are extremely resistant life-forms that play an important role in food spoilage and foodborne disease. The return of spores to a vegetative cell state is a three-step process, these being activation, germination, and emergence. High-pressure (HP) processing is known to induce germination in part of the spore population and even to inactivate a high number of Bacillus spores when combined with other mild treatments such as the addition of nisin. The aim of the present work was to investigate the mechanisms involved in the sensitization of spores to nisin following HP treatment at ambient temperature or with moderate heating leading to a heterogeneous …

Toxicity of fatty acid hydroperoxides towards Yarrowia lipolytica: Implication of their membrane fluidizing action

2007

Abstract Linoleic acid hydroperoxide (HPOD), substrate of hydroperoxide lyase, an enzyme of the lipoxygenase pathway, can be transformed into many aromatic compounds, the so-called “green notes”. The presence of linoleic acid hydroperoxide in the culture medium of Yarrowia lipolytica, the yeast expressing the cloned hydroperoxide lyase of green bell pepper, undoubtedly exerted an inhibition on the growth and a toxic effect with 90% of yeast cells died after 120 min of exposition in 100 mM HPOD solution. The increase in cell membrane fluidity evaluated by measuring fluorescence generalized polarization with the increasing concentration of HPOD in the medium confirmed the fluidizing action of…

High-pressure processing of meat and meat products

2016

International audience; High pressure (HP) was first introduced at the end of the nineteenth century in the field of materials chemistry. The first application of high pressure in the food industry was proposed by Hite in 1899 to pasteurize milk and fruit products. The high hydrostatic pressure (HHP) treatment is considered as a nonthermal process, alternative to heat treatments, as it enables inactivation of pathogenic and spoilage microorganisms in foods. This technology is based on two principles that determine the behavior of foods under pressure. The first is an important principle that underlies the effects on reaction equilibria is known as the principle of Le Chatelier, and the seco…

High Pressure Processing of meat and Seafood

2014

Biopréservation et hautes pressions : des outils pour la maîtrise des dangers microbiologiques dans les aliments

2019

L’utilisation d’additifs conservateurs est souvent nécessaire pour assurer la sécurité microbiologique des produits carnés réfrigérés faiblement acides. Le projet ANR BLac HP (2014-2019) a étudié une nouvelle stratégie de stabilisation des produits carnés réfrigérés pour assurer le contrôle des flores indésirables à la fois végétatives et sporulées. Grâce à une approche pluridisciplinaire, les travaux ont montré que la combinaison de la biopréservation par des bactéries lactiques et d’un traitement hautes pressions permettait d’assurer la qualité microbiologique de dés de jambon cuits à teneur réduite en nitrite pendant toute leur durée de vie. Le traitement permet de plus une qualité senso…

Explorer la biodiversité pour trouver de nouvelles souches microbiennes pour les innovations de produits alimentaires

2015

Référence : 201511122729; Entre les innovations alimentaires renforçant les propriétés sensorielles ou de santé ou améliorant le procédé, la demande de souches microbiennes nouvelles est forte. Toutefois, trouver de nouvelles souches libres de droits et efficaces n’est pas une tâche facile. Dans cet article, seront présentées des voies d’innovations pour augmenter le bénéfice sensoriel de fermentations et les activités du laboratoire international «Tropical Bioresources & Biotechnology» pour découvrir de nouvelles souches et de nouveaux procédés basés sur les fermentations traditionnelles de produits tropicaux.