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Listeria monocytogenes Scott A, serotype 4b, and Yersinia enterocolitica from vacuum-packaged pork were inoculated onto fresh pork chops. Survival and growth were determined in different atmospheres at 4 "C during 35days. Atmospheres were gas mixtures [20/O/80,40/ O/60, and 40/10/50 (COr/OJN,)], vacuum and air. In air L. monocytogenes and Y. enterocolitica grew slower than psychrotrophic spoilage flora. In gas atmospheres, Y, enrerocolirica grew at the same rate as psychrotrophic spoilage flora and L. monocyfogenes grew more slowly. When 10% Or was included in the 40% CO* mixture, growth was reduced. Vacuum packaging was no more effective than gas mixtures in retarding growth. Modified atmospheres provide an environment in the package that would allow growth of Y. enterocolitica and potentially compromise safety of meat products.

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The nutritional requirements of P, K, Mg, and Mn for the mycelial growth of the fungus Pleurotus ostreatus have been studied. Experiments were conducted in submerged culture using a synthetic medium and a peat-extract-based medium. Requirements for both additional phosphorus and additional potassium were detected, and supplementing the peat extract medium with potassium phosphate enhanced the mycelial growth. The addition of yeast extract and potassium phosphate, combined with the peat extract, produced the highest dry biomass concentration in this work, 6.8 g/L. Linear relationships were found between the dry biomass concentration of P. ostreatus and the concentration of KH2PO4 added to the media. No additional requirement for magnesium beyond that existing in the peat extract medium was detected. Supplementing this medium with manganese in the range of 0.1 to 0.15 g/L produced a slight increase in the growth.