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6. Andrich L, Esti M, Moresi M (2009) Urea degradation in model wine solutions by free orimmobilized acid urease in a stirred bioreactor. J. Agric. Food Chem., in press(DOI:10.1021/jf803962b)In this work, a purified acid urease preparation was covalently immobilized on Eupergit C 250 L and stabilizedwith glycine. Its average activity was found to be 69 ( 16% of the initial one after 34-day storage at 4°C. Thekinetics of urea degradation in a model wine solution by immobilized enzyme was confirmed to be of pseudofirst-orderwith respect to the urea concentration in the liquid bulk, its apparent pseudo-first-order kinetic rateconstant (kIi) being about one-fourth of that (kIf) pertaining to the free enzyme. In the operating conditionstested, the reaction kinetics was estimated as unaffected by the contribution of the external film and intraparticlediffusion mass transfer resistances. Because in the presence of the high-inhibitory tannins extracted from grapeseeds in the range of 3-620 g of GAE m -3 the loss in kIi was quite smaller than that in kIf, the biocatalyst testedhere is likely to overcome the present limits to the application of free acid urease in wine treatment.SISTAL - SOCIETA’ ITALIANA DI SCIENZE E TECNOLOGIE ALIMENTARIDipartimento di Scienze e Tecnologie Agroalimentari, Università degli Studi della TusciaVia San Camillo de Lellis, 01100 ViterboTel.: 0761- 35 74 94/7 , Fax: 0761- 35 74 98, e-mail: mmoresi@unitus.it475