BACKGROUND: This paper focuses on the development of temperature induced phase transition hydrogels based on poly(N-isopropylocrylamide (PNIPA) copolymers and their application as an immobilization matrix for biocatalysts. RESULTS: PNIPA-co-AAc and PNIPA-co-MAAc hydrogels were synthesized with different comonomer concentrations and analysed. In order to evaluate the capacity of hydrogels to take up or to release liquids the mass exchange capacity is introduced. In the presented work mass exchange capacities up to 22.4 were realized. To enhance the mechanical stability, composites of hydrogels and cellulosic fleeces were prepared. The enzyme Lipozyme (R) TL 100 L (Thermomyces languniosa Lipase) was successfully inserted into the hydrogels and into the hydrogel composites. Lipase-catalysed transesterification of rapeseed oil with ethanol to the corresponding ethyl ester was investigated to prove the activity of immobilized enzyme and thus, the concept. The activity was found to be similar to that of free enzyme. CONCLUSION: Smart hydrogel composites were used for the transesterification of oil. Based on the results obtained, reversible loadable and mechanical stable hydrogel composites could be developed for continuous working reactor concepts. (C) 2010 Society of Chemical Industry