Akademik Veri Yönetim Sistemi
COLLOIDS AND SURFACES B-BIOINTERFACES, cilt.95, ss.109-114, 2012 (SCI-Expanded)
In this study, cotton terry cloth fibrils were coated with 0.2% polyethyleneimine (PEI). Lipases from Candida antarctica A (CALA) and Thermomyces lanuginosus (TL) were immobilized on this support through adsorption followed by cross-linking with 0.2% glutaraldehyde. PEI-enzyme aggregates formation and growth of aggregates on cotton cloth fibrils lead to multilayer immobilization of the lipases. PEI and lipase was mixed to form PEI-enzyme complex/aggregate. The highest amount of enzyme precipitate was obtained at the PEI to enzyme ratio of 1/20-1/40 for both lipases. The effect of pH was also investigated for aggregates formation. The results showed that when pH values were below 8, aggregation and precipitation were not occurred for C. antarctica A lipase. However, pH did not affect PEI-enzyme aggregate formation for T. lanuginosus lipase. Immobilized enzyme amount was approximately 180 mg/g support and 200 mg/g support for T. lanuginosus and C. antarctica A lipases, respectively. Effect of the reaction temperature on the relative activity of the free and immobilized lipases at various temperature (30-80 degrees C) was studied. It was found that immobilization had no effect on the optimum temperature and it was 60 degrees C for both free and immobilized enzymes. The effect of operational and storage stability on activity of free and immobilized lipases were also investigated. Immobilized lipases exhibited that they could be stored at room temperature with a little activity lost during 28 days. (C) 2012 Elsevier B.V. All rights reserved.