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Porous asymmetric membranes were formed by the phase inversion method from one-to-one blends of polysulphone and its aminated derivative. Amino groups were introduced into polysulphone UDEL P 1700 by chlorosulphonation followed by amination. Urease was immobilized on the modified polysulphone membranes. The properties of the immobilized urease were investigated and related to the free enzyme. The Michaelis constant was 4.4 times higher for the immobilized than for the free urease. Immobilization improved the pH stability of the enzyme at pH < 6.5 as well as its temperature stability. However, the immobilization did not protect the enzyme against heat inactivation at 70 degrees C; the half-times for the activity decay were equal to 120 and 50 min for the free and immobilized enzymes, respectively. The immobilized urease exhibited good storage and operational stability, and good reusability, properties that prove the applicability of the obtained system in enzymatic-membrane reactors.

Polysulfone films were modified by ammonia, n-butylamine and allylamine remote plasma using various sample-to-plasma distances. Contact angle measurements, FTIR-ATR and XPS spectroscopy proved the presence of polar, including amine, groups on the modified surface. Presence of argon in the plasma environment made the plasma more stable and in most cases left the surface more hydrophilic but with a lower amount of nitrogen moieties on it. Glucose isomerase was successfully immobilized on the plasma-treated samples. Its activity correlates well with the concentration of C–N bonds on the surface. The highest enzyme activity was achieved for samples treated with allylamine/Ar plasma close to the plasma edge. [Copyright &y& Elsevier]