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bacterium Alicyclobacillus acidocaldarius: Identification of the active site residues . Biochim. Biophys. Acta , 1784 , 292 – 301 . L OWRY , O.H. , R OSEBROUGH , N.J. , F ARR , A

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Abstract

There are numerous biological agents including bacteria such as Brucella suis, B. abortus, Francisella tularensis, Burkholderia mallei, Coxiella burnetii, Yersina pestis, Bacillus anthracis and Chlamydia psittaci, viruses such as Variola major and V. minor, Flavivirus and Hantavirus, and toxins such as Botulinum toxin produced by the bacterium Clostridium botulinum, Staphylococcus enterotoxin B and Trichothecene mycotoxin reported to have potential to cause illness via water consumption. In the recent years, biological threat prevention for urban water supply systems has been of special interest worldwide, thus, protection against biological agents requires adequate knowledge, available water treatment technologies and preparedness. In this review, the history of biological threat via public water supply, as well as selected early detection methods, prevention strategies and risk assessment models are detailed.

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Acta Alimentaria
Authors: N. Topic Popovic, A. Benussi Skukan, P. Dzidara, I. Strunjak-Perovic, S. Kepec, J. Barisic and R. Coz-Rakovac

.B.R. ( 1926 ): A disease of rabbits characterized by a large mononuclear leucocytosis, caused by a hitherto undescribed bacillus Bacterium monocytogenes (n.sp.) . J. Pathol.Bacteriol ., 29 , 407 – 439

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In this study, detection of an obligate aerobic, thermophilic and acidophilic bacterium, the sporeforming Alicyclobacillus acidoterrestris was performed by determination of its specifc metabolite, guaiacol. Since its spores have been shown to resist conventional pasteurization, it has become a potential spoilage concern for fruit and vegetable juices, mainly for apple and orange juices. Detection of guaiacol was carried out by using an NST 3320 type electronic nose, and other methods, such as peroxidase-based enzymatic method with UV-Vis spectrophotometer, SPME-GC-MS technique and an untrained sensory panel were also applied. The results indicated that based on their detection limit the methods can be ordered in the following way: SPME-GC-MS (detection limit: <0.5 ppm)<sensory evaluation (detection limit: 0.5–1 ppm)<spectrophotometric method=electronic nose technique (detection limit: 1.25–2.5 ppm).

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Acta Alimentaria
Authors: J. A. Grahovac, Z. Z. Rončević, I. Ž. Tadijan, A. I. Jokić and J. M. Dodić

Bacillus subtilis is one of the most important producers of diverse antimicrobial compounds. This bacterium grows and produces antibiotics on different substrates. The increase of the antibiotics yield can be achieved by changing the conditions of cultivation and the composition of the culture media. In this study, response surface methodology was used for optimization of glycerol, sodium nitrite, and phosphate content in media for production of antibiotics effective against Staphylococcus aureus. As biosynthesis strain Bacillus subtilis ATCC 6633 was used. The developed model predicts that the maximum inhibition zone radius (38.08 mm) against Staphylococcus aureus and minimal amount of residual nutrients (glycerol 1.75 g l−1, nitrogen 0.21 g l−1, phosphorus 0.18 g l−1) are achieved, when the initial content of glycerol, sodium nitrite, and phosphate are 49.99 g l−1, 1.00 g l−1, and 5.00 g l−1, respectively.

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Acta Alimentaria
Authors: K. Régaiszné Vajda, A.A. Halbritter, P. Szűcs, J. Szigeti and B. Ásványi

Sous-vide (French for ʽunder vacuum’) is a professional cooking method, by which, under oxygen-free conditions and precise temperature control, not only cooking but preservation is achieved. During the process the food matrix is vacuum-packed and undergoes a mild heat treatment, thus achieving an enhanced nutrition value and a better organoleptic character. Due to the mild heat treatment (55 to 90 °C), the high water activity, and the slight acidity of raw materials, the microbial quality assurance is a great challenge even for professionals. The heat treatment does not assure the inactivation of pathogen spores. In our experiments we used Clostridium perfringens representing the spore-forming pathogens, and Salmonella Enteritidis as a the food-borne infection bacterium. Effects of various temperatures were measured in normal and sous-vide type vacuum packaging. Higher thermal death rate in vacuum packaging was demonstrated for Salmonella Enteritidis and Clostridium perfringens.

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In this study, the antibacterial and antioxidant activities of dried fruit extract of cranberry (gilaburu, Viburnum opulus) were determined. The total phenolic content was found to be 131.99±2.11 mg gallic acid equivalent (GAE) g-1 in the cranberry fruit extract (CFE). The antioxidant activity of the extract was found to be 315.50±8.2 mg g-1 in dried methanol extract. At 2, 5, 10 and 15% concentrations the extracts were tested for their antibacterial effects by using the agar diffusion method against ten bacteria, some of them pathogenic and some of them spoilage microorganisms. All bacteria were inhibited by 10 and 15% concentrations of the CFE. Methanol (control) had no inhibitory effect on all the tested bacteria. The most sensitive of the bacteria was A. hydrophila, whereas the most resistant bacterium was Y. enterocolitica.

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Examination of heat shock and PR (“pathogenesis-related”) proteins is of special interest in food science. Many food allergens have a similar or the same structure as PR proteins, which are produced in the plants as a response to pathogenesis or certain environmental stresses. The protein set of the psychrophilic bacterium Shewanella hanedai was studied by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). Gel patterns from control and heat-treated bacteria were evaluated by PDQUEST software. The differentially expressed proteins were excised from the gel and digested by trypsin. The tryptic peptides were analysed by nanoflow LC-MS/MS. On the basis of amino acid sequences obtained by this method, the proteins were identified by similarity searching in the protein database. Using this proteomic approach a heat shock and a 50S ribosomal protein were identified as the major heat induced proteins in Shewanella hanedai.

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The aim of this study was to investigate the effect of some food additives used in foods on cold tolerance of Clostridium perfringens at pH close to neutral.Maximal concentrations recommended for foods of sodium benzoate, potassium sorbate, sodium nitrite, monosodium glutamate, or mixtures of those were added to cultures and their effects on C. perfringens tolerance to 10 °C were evaluated. The effect of a previous shock at 28 °C was also determined. Growth of C. perfringens was not inhibited by the substances examined. Sodium nitrite, applied at maximal permitted concentrations, increased C. perfringens survival at 10 °C. Mixtures of GRAS compounds had either no clear effect, or increased tolerance to 10 °C. A pre-shock (28 °C) of the cultures treated with sodium benzoate, sodium nitrite or monosodium glutamate increased survival and stimulated growth of the cultures treated at 10 °C.We conclude that the addition of these compounds including sodium benzoate, potassium sorbate, sodium nitrite and monosodium glutamate to cultures of C. perfringens can influence their cold tolerance. In some cases, the substances that would normally eliminate microorganisms at lower pH, can increase tolerance of this bacterium, permitting survival at low temperatures.

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Lactic acid bacteria isolated from commercially produced alfalfa sprouts were screened for activity against Listeria monocytogenes F4258. Most active isolates were identified as Lactococcus lactis subsp. lactis. The isolates fell into two categories, strains that inhibited by acid production only, and strains that appeared to have additional inhibitory activity. An acid-only isolate, SP26, was used to evaluate the effect of initial pH (5, 6, 7, 8) and temperature (10, 20, and 30 °C) on the interaction between the lactic acid bacterium and L. monocytogenes using “sprout juice” as a model system. The model system was inoculated with an initial level of approx. 103 CFU ml-1 L. monocytogenes in both mono-culture controls and the co-cultures and the co-cultures with L. lactis (103-104 CFU ml-1). The primary inhibitory effect attributable to L. lactis was a 2 to 3 log cycle decrease in the maximum population density obtained by L. monocytogenes. The extent of the inhibition was decreased at 10 °C, but was only slightly affected by pH in the range of 6.0 to 8.0. L. monocytogenes did not grow in the sprout broth at pH 5.0 at any of the incubation temperatures.

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