Modelling the risk of mortality of Corbicula fluminea (Müller, 1774) (Bivalvia: Corbiculidae) exposed to different turbidity conditions.

The provision of sediment in rivers, due to erosion processes that occur in the environment, consists of a major source of pollution and alteration of the physicochemical conditions of water resources. In addition, the increase in water turbidity may cause siltation, dramatically impacting aquatic communities. Specifically considering the bivalve Corbicula fluminea (Müller, 1774), the aim of this study was to analyse the effect of exposure to different turbidity conditions of sediments, as a risk factor for the animals. For this purpose, a docking device was designed to ensure water circulation in a closed system and to maintain the desired levels of turbidity. Although C. fluminea can generally tolerate environmental changes in aquatic systems, an intolerance to high turbidity levels was experimentally observed, expressed by the mortality rate of the animals when exposed to conditions above 150 nephelometric turbidity units (NTU). This value was similar to the one recorded at study sites in the rivers Pardo (Serrana-SP-Brazil) and Mogi Guaçu (Porto Ferreira-SP-Brazil) during the rainy season. Using a logistic regression model, the experimental results were analysed and the observed mortality rates indicate that the exposure of the animals to turbidity levels above 150 nephelometric turbidity units (NTU), for periods longer than 120 hours, may be considered a probable cause of mortality for the species.

Antilisterial activity of lactic acid bacteria inoculated on cooked ham.

This study was conducted to evaluate the ability of Lactobacillus sakei 1, a bacteriocin-producing (bac(+)) lactic acid bacterium (LAB), isolated from Brazilian fresh pork sausage to inhibit two Listeria monocytogenes strains (serotypes 4b and 1/2a) on cooked, sliced vacuum-packaged ham. L. sakei ATCC 15521 was used as a non-bacteriocin producer (bac(-)). L. monocytogenes (ca. 2 logCFU/mL) and LAB (ca. 6 logCFU/ml) were inoculated on the sterilized ham, vacuum-sealed and incubated at 8°C for 10 days. A treatment with the bacteriocin Chrisin (UI/ml) was included. Both L. monocytogenes strains were significantly inhibited in the presence of either bac(+) and bac(-) LAB in comparison to the control (L. monocytogenes alone). Using a bacteriocinogenic strain of LAB did not offer an additional barrier to listerial growth in the studied meat system. The application of Chrisin did not affect at all the growth of L. monocytogenes.

A simple protocol for the routine calibration of pH meters

Um protocolo laboratorial simples para calibração de peagâmetros é descrito e testado, baseado no uso de soluções de padrões primários:biftalato de potássio e Bórax (tetraborato de sódio decaidratado), de concentração e pH exatos e conhecidos.As soluções se conservam bem à temperatura ambiente, por tempo prolongado, sem necessidade de refrigeração.A calibração pode ser conferida usando soluções padrão de dihidrogeno fosfato de sódio, de carbonato de sódio, de benzoato de sódio, de salicilato de sódio ou de oxalato de potássio. Métodos para purificação de Bórax e de cloreto de potássio são descritos, bem como é sugerido um novo método de neutralização de solução de cloreto de sódio 0,9 por cento