Immobilization of enzymes is one of the most promising methods in enzyme performance enhancement, including stability, recovery, and reusability. However, investigation of suitable solid support in enzyme immobilization is still a scientific challenge. Polyethersulfone (PES) and aminated PES (PES–NH2) were successfully synthesized as novel materials for immobilization. Membranes with various pore sizes (from 10–600 nm) based on synthesized PES and PES–NH2 polymers were successfully fabricated to be applied as bioreactors to increase the immobilized lipase performances. The influence of pore sizes, concentration of additives, and the functional groups that are attached on the PES backbone on enzyme loading and enzyme activity was studied. The largest enzyme loading was obtained by Mucor miehei lipase immobilized onto a PES–NH2 membrane composed of 10% of PES–NH2, 8% of dibutyl phthalate (DBP), and 5% of polyethylene glycol (PEG) (872.62 µg/cm2). Hydrolytic activity of the immobilized lipases indicated that the activities of biocatalysts are not significantly decreased by immobilization. From the reusability test, the lipase immobilized onto PES–NH2 showed a better constancy than the lipase immobilized onto PES (the percent recovery of the activity of the lipases immobilized onto PES–NH2 and PES are 97.16% and 95.37%, respectively), which indicates that this novel material has the potential to be developed as a bioreactor for enzymatic reactions.

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Background: Nowadays, biodiesel has become more attractive in the quest for a novel fuel source due to its environmental benefits and the biodegradable properties. Transesterification of Helianthus annuus (sunflower) seeds oil is one of methodsacci for producing biodiesel fuel. However, during this process, the impurities are frequently found in the synthesized biodiesel which degrades the quality of biodiesel. Therefore, a proper catalyst is required to obtain the high-quality biodiesel. In this study, a series of aminated polyethersulfone (PES-NH 2 ) membranes was prepared as solid support for immobilized Mucor miehei lipase. Glutaraldehyde was used as a cross-linker agent in immobilization process to investigate the effect of spacer toward biodiesel production.Results: Based on elemental analysis, lipase was successfully attached onto PES-NH 2 membranes and formed physical interactions. Enzyme loading values of synthesized membrane were higher than that of commercial filtration membrane. LC-MS analysis with C18 as a column showed that butyl palmitate, butyl linoleate, and butyl oleate were produced from transesterification reaction of triglyceride from sunflower oil and butanol. Based on FTIR analysis, the imine group as a covalent bond was successfully obtained during the cross-linking reaction. After reaction with the spacer, the enzyme loading was increased significantly from 177.05 to 911.48 μg/cm 2 . The alkyl esters produced also showed high values after the cross-linking. According to biodiesel quality tests, the results were matched with the values specified by the ASTM. Conclusion:Biodiesel from sunflower seeds oil was successfully synthesized through a transesterification reaction catalyzed by Mucor miehei lipase immobilized onto the synthesized aminated PES membrane. The addition of glutaraldehyde as a cross-linker showed an excellent enzyme loading value and led to significantly increased biodiesel conversion efficiency. This method is good to be developed, since the immobilized enzyme stability could be increased, the separation process was easier, and a high yield with good quality of biodiesel could be obtained.

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