Poly(styrene-co-acrolein) (P(S/A)) microspheres were synthesized by emulsifier-free emulsion-dispersion radical copolymerization of styrene and acrolein. Particles with a number average diameter ( øD n ) of 373 nm, a narrow diameter distribution ( øD w / øD n ) of 1.008 and a surface concentration of aldehyde groups from polyacrolein units of 2.51 · 10 −6 mol/m 2 were obtained. Ureases from jack beans (Urs-JB) and from pigeonpea (Urs-PP) were immobilized onto these microspheres. Activity of free and immobilized urease was determined using a standard phenol method. Surface concentration of attached enzymes was varied in the range from 0.06 to 1.6 mg/m 2 . Specific activity of Urs-JB in solution was 1.9 times higher than that of Urs-PP, however, upon immobilization of enzymes onto P(S/A) microspheres the reverse was true. Due to very high denaturation activity of immobilized Urs-JB was 10 times lower than in solution. In the case of Urs-PP, denaturation of the enzyme upon immobilization was much lower and possibly due to a cooperative effect resulting from a local high concentration of immobilized enzyme, its specific activity was from 3 to 9 times higher than that of immobilized Urs-JB.
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Kayastha et al. (2003) studied this question.
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