ENTRAPMENT OF UREASE IN GLYCOL-CONTAINING POLYMERIC MATRICES AND ESTIMATION OF EFFECTIVE DIFFUSION-COEFFICIENT OF UREA

Urease enzyme was immobilized in copolymer matrices containing poly(et hylene glycol) (PEG; MW 14000 and 1000) or polypropylene glycol (PPG; MW 2000), prepared with 2-hydroxyethyl methacrylate (HEMA) and/or N-vi nyl-2-pyrrolidone (VP). Urease-immobilized copolymer matrices were sto red in phosphate buffer solutions of pH 7.0 at 4 degrees C, and the ac tivity of the enzyme was determined periodically for up to 90 days. Th e highest activity was observed for HEMA and VP containing PEG (MW 140 00) matrix. The matrices comprising VP and PEG (MW 14000) did not have mechanical stability and degraded in 3 weeks, while all the others we re stable and demonstrated enzyme activities for up to 3 months. The e ffective diffusion coefficients of urea in these polymer matrices were calculated with a 'diffusion and reaction model' and the highest effe ctive diffusion coefficient was found in the HEMA and VP containing PE G matrix, possibly due to its highly porous structure.