Immobilization and activity of Rhizomucor miehei lipase. Effect of the matrix properties prepared from nonionic fluorinated surfactants

We report the immobilization of Rhizomucor miehei lipase (RmL) onto mesoporous silica materials, in particular the investigations concerning the effects of the level of silica condensation and of the pore size on the enzyme activity. The efficiency of the immobilization was revealed by FTIR spectroscopy. Infrared was also used to determine the quantity of adsorbed enzyme. Immobilization efficiency increased when the RmL concentration in the buffer solution was changed from 2 to 10 mg/mL. Nevertheless, while upon enzyme immobilization the mesopore ordering was sustained for the support recovered after hydrothermal treatment at 100 °C, a structure collapse occurred for the one prepared at 80 °C. The difference in behavior is attributed to the lower hydrothermal stability of this material, which reflects the lower level of silica condensation. The enzyme-containing mesostructured silica was effectively used to catalyze the model esterification reaction of lauric acid with 1-propanol, as the immobilized lipase retained its catalytic activity. A linear relationship was observed between the reaction rate and the amount of catalyst. RmL immobilized on mesoporous materials presented a satisfactory reusability, while the remaining activity of RmL after 4 months of storage was 47% of the initial one.