Laccase enzyme (L) from Trametes versicolor was entrapped in three hydrogel structures namely poly(acrylamide-N-isopropylacrylamide), P(AAm-NIPA), and semi-interpenetrating networks of poly(-acrylamide)/alginate, P(AAm)/Alg, and poly(acrylamide-N-isopropylacrylamide)/alginate, P(AAm-NIPA)/Alg. The optimum temperatures for free and all immobilized systems were found to be 40 degrees C. For free and immobilized laccase systems of P(AAm-NIPA)-L, P(AAm)/Alg-L and P(AAm-NIPA)/Alg-L, K-m values were found to be 6.7 x 10(-3), 8.8 x 10(-2), 5.5 x 10(-2) and 1,8 x 10(-2) mM: V-max values were calculated as 1.8 x 10(-3). 2.5 x 10(-2), 1.5 x 10(-2) and 6.1 x 10(-3) mM min(-1), respectively. For free and the same immobilized systems, the enzymes retained 42%, 91%. 79% and 86% of their initial activities at the end of 56 days of storage. After using the mentioned immobilized systems repeatedly 10 times, they retained 77%, 71% and 84% of their original activities, respectively. For free and the same immobilized systems, decolorization of Acid Orange 52 (AO52) in 6 h were found to be 63%, 50%, 48% and 66%, respectively. Addition of 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid), ABTS, into the assay medium increased these values LIP to 73%, 73%, 74% and 75%, respectively. (C) 2008 Elsevier Ltd. All rights reserved.