David O'Beirne

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Escherichia coli fed-batch cultivations at 22 m3 scale were compared to corresponding laboratory scale processes and cultivations using a scale-down reactor furnished with a high-glucose concentration zone to mimic the conditions in a feed zone of the large bioreactor. Formate accumulated in the large reactor, indicating the existence of oxygen limitation(More)
Enzymatic crosslinking provides valuable means for modifying functionality and structural properties of different polymers. Tyrosinases catalyze the hydroxylation of various monophenols to the corresponding o-diphenols, and the subsequent oxidation of o-diphenols to the corresponding quinones, which are highly reactive and can further undergo non-enzymatic(More)
The survival and growth of Escherichia coli O157:H7 (ATCC 43888 and NCTC 12900) and Listeria monocytogenes (ATCC 19114 and NCTC 11994) during storage (4 and 8°C) on ready-to-use (RTU) packaged vegetables (lettuce, swedes (rutabaga), dry coleslaw mix, soybean sprouts) were studied. The vegetables were sealed within oriented polypropylene packaging film, and(More)
AIMS To establish the relative importance of the osmo- and cryoprotective compounds glycine betaine and carnitine, and their transporters, for listerial growth and survival, in foods and during infection. METHODS AND RESULTS A set of Listeria monocytogenes mutants with single, double and triple mutations in the genes encoding the principal betaine and(More)
AIMS The contribution of the glutamate decarboxylase (GAD) acid resistance system to survival and growth of Listeria monocytogenes LO28 in modified atmosphere-packaged foods was examined. METHODS AND RESULTS The survival and growth of the wild-type LO28 and four GAD deletion mutants (DeltagadA, DeltagadB, DeltagadC, DeltagadAB) in packaged foods (minced(More)
The growth dynamics of indigenous aerobic mesophilic populations (AMP), lactic acid bacteria (LAB) and inoculated (Listeria spp.) microbial populations on cooked and fresh vegetable products, packaged as separate entities and in combination, subjected to temperature fluctuation, were assessed. Microbial proliferation was temperature and product dependent,(More)
The reported benefits of enrichment of air atmospheres with argon or oxygen for control of enzymatic browning were investigated by determining the effects of these atmospheres on PPO kinetics. Kinetics of purified apple PPO and a commercially available mushroom PPO were studied in an in vitro model system. Enrichment with argon produced greater inhibitory(More)
Natural antimicrobials such as plant essential oils (EOs) may be useful for controlling pathogenic bacteria on fresh-cut vegetables. The antilisterial properties of EOs (thyme, oregano, and rosemary), in combination with different storage atmospheres (air, 5% CO2-2% O2-93% N2, and 20% CO2-1% O2-79% N2) and temperatures (4 and 80C), were examined using a gas(More)
The aim of this study was to use confocal scanning laser microscopy to examine the in situ localization of Escherichia coli O157:H7 on beef (knuckle or brisket) and carrots and in semisoft cheese made from pasteurized milk. Using a combination of specific immunolabeling and dual-excitation confocal scanning laser microscopy, it was possible to clearly(More)
The incidence of Listeria monocytogenes in modified atmosphere packaged fresh-cut fruits and vegetables from chill cabinets of a supermarket in Ireland was investigated over a 2-year period. Overall, 9.58% of fresh-cut produce was contaminated with Listeria spp. Various species of Listeria were isolated from samples, including L. monocytogenes, L.(More)