Various Types of Lipases Immobilized on Dendrimer-Functionalized Magnetic Nanocomposite and Application in Biodiesel Preparation

Three sub-group lipases of Burkholderia cepacia lipase (BCL), Rhizomucor miehei lipase (RML), and Candida rugosa lipase (CRL) were covalently immobilized on dendrimer functionalized magnetic carbon nanotube and used as catalysts to catalyze biodiesel production. The effects of imprinting molecule, organic solvent, water, methanol, temperature and time interval, of methanol addition on the yield of biodiesel were optimized. The results showed that bioimprinting could greatly enhance catalytic performances of the three immobilized lipases. The obtained lipases were then employed to catalyze biodiesel production, and the achieved optimum conditions were: for BCL, water content 5 wt. %, reaction temperature 35 degrees C, and with tbutanol as reaction medium, methanol : oil molar ratio 4:1, its highest biodiesel yield attained 96.4%; for RML, water content 10 wt. %, reaction temperature 50 degrees C, n-octane as the reaction medium, methanol : oil molar ratio of 5:1, the utmost biodiesel conversion rate was up to 96.2%; and for CRL, water content 7.5 wt. %, reaction temperature 40 degrees C, isooctane as the reaction medium, methanol:oil molar ratio of 4:1, the best yield reached 85.1%. It was borne out that the effect of time interval of methanol addition on the biodiesel conversion was more obvious for the immobilized RML and CRL than BCL. Furthermore, waste vegetable oil was also explored for biodiesel preparation vs soybean oil. It reveals that the immobilized RML exhibited best catalysis toward both feedstock in its corresponding solvent systems.