Activity and Stability of Lipases Immobilized onto Acetylated Bacterial Cellulose

Abstract

Bacterial cellulose (BC) materials were used for lipase immobilization to improve enzyme activity and stability. BC films produced by Komagataeibacter xylinus were first acetylated in an acetic anhydride/iodine system to convert their OH groups to more hydrophobic acetyl groups. Activity yield (44.4%) and maximum specific activity (12.44 μmol mg–1 min–1) were achieved when 400 mg of BC was acetylated in 20 mL of acetic anhydride containing 0.275 mM of iodine. Studies on the catalytic activity of lipase also show that the immobilization of lipase on acetylated BC (ABC) films significantly enhanced its tolerance to temperature and pH. Immobilized lipases retained 89% and 56% of their catalytic activities after being incubated at 60 °C and 80 °C for 1 h, respectively; while those of free lipases significantly decreased to 24% (60 °C) and only 11% (80 °C). Immobilized lipases incubated at pH 5.0 and pH 10.0 for 24 h also retained high catalytic activities (70% and 82%, respectively), considerably higher than those of free lipases (19% - pH 5.0 and 63% - pH 10.0). Tolerance to organic solvents, such as n-hexane, acetone, ethanol, isopropanol of ABC-immobilized lipase was also improved. The immobilization of lipase on ABC films significantly improved its reusability and storage stability: ABC-immobilized lipase still could be reused for 30 cycles with residual activities of more than 90%, and still retained 95% of its early activity after 15-day storage at 4 °C. This implies that ABC-immobilized lipase is potentially applied in food, medicine, biodiesel and detergent industries.