Surface Modification of Magnetic ZIF-90 Nanoparticles Improves the Microenvironment of Immobilized Lipase and Its Application in Esterification

Abstract

Interactions of enzymes with supports significantly affect the activity and stability of immobilized enzymes. Herein, amino-functionalized ionic liquid (IL)-grafted magnetic zeolitic imidazolate framework-90 (MZIF-90) was prepared and used to immobilize porcine pancreatic lipase (PPL). The nanocomposites were fully characterized; meanwhile, the interactions between ILs and ZIF-90 were calculated based on density functional theory. The prepared biocatalyst (PPL-ILs/MZIF-90) had a lipase loading of 178.3 mg/g and hydrolysis activity up to 287.5 U/g. When the biocatalyst was used to synthesize isoamyl acetate, the reaction media, molar ratio of alcohol/acid, temperature, and reaction time were optimized. Under the optimized reaction conditions (in hexane, alcohol/acid = 3:1, under 45 °C, reacted for 9 h), the ester yield reached 85.5%. The results of the stability test showed that PPL-ILs/MZIF-90 retained 88.7% of the initial activity after storing for 35 days and 92.5% of the initial activity after reusing for seven cycles for synthesizing isoamyl acetate. Moreover, the secondary structure analysis showed that the synthesized supports protected the active conformation of immobilized lipase, which lead to the enhanced catalytic performance. Additionally, the biocatalyst can be easily separated with a magnet, which facilitated the reusability. This study provides insights regarding the application of metal organic framework composites in the field of enzyme catalysis.

Functionalized Ionic Liquids-Modified Metal–Organic Framework Material Boosted the Enzymatic Performance of Lipase

“…Most recently, our team investigated IL-modified MOF (IL-NH 2 -MIL-101) for laccase immobilization, which confirmed that immobilized enzymes exhibited improved stability and activity, and achieved efficient pollutant degradation rates [17]. Moreover, Suo et al [18] developed amino-functionalized IL-grafted magnetic MOF (ZIF-90) for the immobilization of porcine pancreatic lipase (PPL-ILs/MZIF-90), which demonstrated the high esterification efficiency of synthetic isoamyl acetate. The introduction of IL enhances the binding between the enzyme and the carrier, improves the flexibility of the carrier on the surface of the enzyme, and further alters the structural conformation of the lipase.…”

Metal–organic framework-supported ionic liquids for lipase immobilization: design, characterization, and investigation of catalytic performance

“…At pH 6.5, PPL-ILs/MCaBDC showed a residual activity of 63.4% which was higher than that of PPL immobilized on IL modified MZIF-90 (51.6%) as reported. 50 This phenomenon indicated that PPL-ILs/MCaBDC was more stable under acidic conditions because of the good stability of CaBDC-MOF at acidic pH. 51 Fig.…”