Covalent immobilization of lipase onto citric acid-esterified loofah sponge

Loofah sponge was activated by thermochemical esterification between the carboxyl groups of citric acid and hydroxyl groups of cellulose to introduce free carboxyl groups, which were further reacted with lipase amino groups with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) as the condensing reagent. This resulted in loofah sponge-immobilized lipase. Under the optimized immobilization conditions, the highest activity of immobilized lipase per gram of dry carrier was found to be 45.8 U/g. The immobilized lipase exhibited maximum activity at 40 degrees C, pH 8.0, while the optimal temperature and pH for the free lipase were 37 degrees C and 7.5, respectively. The immobilized lipase showed better thermal stability, storage stability, and reusability than free lipase.