Molecular Catalysis

The present work reports on the use of a hybrid blend of biopolymers as a matrix for lipase immobilization. (Hydroxypropyl)methyl cellulose (HPMC) and Chitosan (CS) were combined in order to formulate a film on which Mucor miehei lipase was immobilized. The biocatalyst was studied upon the model reaction of propyl laurate synthesis. The system was examined in terms of its capability to provide an appropriate environment where lipase will maintain its activity. The ratio of the polymers used was examined and HPMC:CS=2:1 proved to form the most promising matrix. Increasing the amount of the immobilized enzyme appears to improve the reaction yield indicating, however, mass transfer limitations. Apparent activation energy was calculated and energy input showed that ultra-sonication accelerated the initial rate of the reaction. Different reaction solvents were tested with isooctane being the most effective. The enzyme-containing film showed a remarkable reusability, since it can be used for up to 35 times without loss of activity. Finally, Atomic Force Microscopy (AFM) was performed to observe the morphology of the most promising films. The HPMC/CS film exhibits a nanostructure without a unique characteristic length and a roughness of 42.8 nm while the presence of enzyme smoothens the film as the roughness decreases to 5.5 nm