Immobilized lipase on MIL-53(Al)-AM11 with regulatable hydrophobic surface for flavor ester synthesis.

Enzymatic synthesis of flavor esters is crucial for applications in food, beverage, and cosmetics industries. However, the poor activity and stability of free lipase hinder these reaction. Inspired by the concept of lipase interface activation, MIL-53(Al)-NH2 was modified with alkyl acid anhydrides of varying chain lengths to tailor its hydrophobicity, and Candida Rugosa lipase (CRL) was subsequently immobilized on this surface to achieve efficient interface activation. The resulting CRL@MIL-53(Al)-AM11 exhibited 3.5 times higher activity than the unmodified CRL@MIL-53(Al)-NH2. Moreover, CRL@MIL-53(Al)-AM11 enabled one-step purification of crude CRL via selective adsorption. It also showed enhanced storage and thermal stability as well as higher resistance to protease degradation and denaturants than free CRL. CRL@MIL-53(Al)-AM11 retained 75 % of its initial activity after 30 min treatment at 55 °C, whereas the free CRL retained only 41 %. After 11 days of storage, CRL@MIL-53(Al)-AM11 maintained 70 % of its initial activity, in contrast to 36 % for the free lipase. Notably, CRL@MIL-53(Al)-AM11 achieved a 97 % conversion rate in the esterification synthesis of the flavoring substance (butyl butyrate) within 24 h and retained over 40 % conversion after five consecutive cycles. Therefore, this strategy offers a feasible approach for constructing high-performance immobilized lipases for flavor ester synthesis.