-Partial hydrolysis of whey proteins by enzymes immobilized on an inert support can either change or evidence functional properties of the produced peptides, thereby increasing their applications. The hydrolysis of sweet cheese whey proteins by alcalase, which is multipoint-immobilized on agarose gel, is studied here. A MichaelisMenten model that takes into account competitive inhibition by the product was fitted to experimental data. The influence of pH on the kinetic parameters in the range 6.0 to 11.0 was assessed, at 50 o C. Initial reaction-rate assays in a pHstat at different concentrations of substrate were used to estimate kinetic and Michaelis-Menten parameters, k and K M . Experimental data from long-term batch assays were used to quantify the inhibition parameter, K I . The fitting of the model to the experimental data was accurate in the entire pH range.

A great amount of heavy metals enter Pampulha Reservoir via it's main tributaries (Sarandi and Ressaca). Although no water quality classification has been carried out for these tributaries, the reservoir is expected to be in class 2 of the CONAMA-86 system. As part of a monitoring scheme of the Pampulha Watershed, heavy metals (Zn, Pb, Cd, Ni, Cu, Cr, Mn and Fe) were investigated in the water at a control site (considered free from direct human influence) and at potential sites of toxicity and contamination during August A relatively high concentration of cadmium was also detected at the confluence of the two streams. During the second sampling period, there was an increase in the concentrations of zinc at all sampling sites except the control, with values varying from 0.71 mg.L -1 (the Sarandi Stream) to 2.50 mg.L -1 (the Ressaca Stream). Lead, cadmium, nickel and chromium concentrations were also higher in the Ressaca Stream, but not detected at the other sampling sites. Copper values were higher than in the first period: 0.10 mg.L -1 at the control up to 0.38 mg.L -1 at the confluence of the streams. Similar results were found for manganese and iron, with values reaching up to 19.30 and 125 mg.L -1 , respectively. Moreover, all values recorded in the second sampling period were much higher than recommended for class 2 waters. These results emphasize the need for such monitoring in relation to better water quality management of this reservoir. Key words: heavy metals, monitoring, Pampulha Watershed, water quality. RESUMO Metais pesados em tributários da represa da Pampulha, Minas GeraisOs efluentes lançados nos principais tributários da represa da Pampulha (Sarandi e Ressaca) estão em grande parte representados por metais pesados. Embora não haja enquadramento para a qualidade da água destes tributários, por apresentarem trechos canalizados, os limites recomendados para o reservatório o classificam como classe 2. Dentre os aspectos ecotoxicológicos considerados no monitoramento da Bacia da Pampulha, foram investigados teores de metais pesados (Zn, Pb, Cd, Ni, Cu, Cr, Fe e Mn) na água, em locais com potencial de toxicidade e contaminação, durante agosto (estação seca) e novembro/98 (estação chuvosa). Os primeiros resultados mostraram concentrações relativamente elevadas de zinco (0,22 mg.L -1 ) na porção inicial do reservatório. No início do Córrego Sarandi, foram encontrados os maiores teores de níquel e cromo (0,19 e 0,89 mg.L -1 , respectivamente), enquanto as maiores concentrações de chumbo (0,05 mg.L -1 ), cádmio (0,014 mg. L -1 ), manganês (0,43 mg.L -1 ) e ferro (15,25 mg.L -1 ) foram encontradas no Córrego Ressaca, onde está situado o aterro sanitário de Belo Horizonte. Uma concentração relativamente elevada de cádmio também foi verificada Braz. J. Biol., 61(3)

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