title: Advantages of using non-isothermal bioreactors in agricultural waste water treatment by means of immobilized urease. Study on the influence of spacer length and immobilization method.
abstract: The behavior of three different catalytic membranes, obtained by immobilizing urease on nylon sheets chemically grafted with methyl methacrylate, was studied in a bioreactor operating under isothermal and non-isothermal conditions. Membrane activation was carried out by condensation or acyl azide reaction, and spacers of different lengths, such as hexamethylendiamine or hydrazine, were used. Under isothermal conditions, the activities of the catalytic membranes and soluble urease were characterized as a function of pH, temperature, and urea concentration. Both enzyme forms showed the same optimum pH, whereas the optimum temperature was lower for the immobilized enzymes. The spacer length appeared to determine broader pH- and temperature-activity profiles for the urease derivatives. The apparent K(m) values of the insoluble urease were dependent on membrane type and were higher than those of the soluble counterpart, thus indicating an affinity loss for urea. Under non-isothermal conditions, all membranes exhibited an increase of percentage activity proportional to the applied temperature difference and decreasing with the increase of urea concentrations. A decrease of the apparent K(m) was also observed. These results suggest that substrate diffusion limitations due to the immobilization process can be overcome in the presence of temperature gradients. In addition, the remarkable reduction of the production times supports the use of non-isothermal bioreactors for the treatment of urea-polluted waste waters.
authors: International Institute of Genetics and Biophysics of CNR, Via G. Marconi 12, 80125 Naples, Italy.
authors: Hazem
authors: H
authors: El Sherif
authors: Silvana
authors: S
authors: Di Martino
authors: Paola
authors: P
authors: Travascio
authors: Anna
authors: A
authors: De Maio
authors: Marianna
authors: M
authors: Portaccio
authors: Daniela
authors: D
authors: Durante
authors: Sergio
authors: S
authors: Rossi
authors: Paolo
authors: P
authors: Canciglia
authors: Damiano G
authors: DG
authors: Mita
mesh_terms: D000383:Agriculture; D019149:Bioreactors; D004800:Enzymes, Immobilized; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008567:Membranes, Artificial; D013696:Temperature; D013816:Thermodynamics; D014510:Urease; D018505:Waste Management / Q000379:methods*
chemical_list: D004800:Enzymes, Immobilized; D008567:Membranes, Artificial; D014510:Urease