Abstract
The cross-linked enzyme aggregates (CLEAs) are one of the technologies that quickly immobilize the enzyme without a carrier. In this study, ionic liquid with amino group (1-aminopropyl-3-methylimidazole bromide, FIL) was used as the novel functional surface molecule to modify CRL (Candida rugosa lipase, CRL). The enzymatic properties of CRL-FIL-CLEAs were investigated. The activity of CRL-FIL-CLEAs (5.51 U/mg protein) was 1.9 times higher than that of CRL-CLEAs (2.86 U/mg protein) without surface modification. After incubating in a centrifuge tube for 50min at 60°C, CRL-FIL-CLEAs still maintained 61% of its initial activity, while the value for CRL-CLEAs was only 22%. After repeated use for five times, compared with the 22% residual activity of CRL-CLEAs, the value of CRL-FIL-CLEAs was 51%. Based on the above results, it was indicated that this method provided a new idea for the effective synthesis of immobilized enzyme.
Highlights
Lipase (EC 3.1.1.3) is a very unique biocatalyst with interface activation mechanism [1]
The results showed that the activity of Candida rugosa lipase (CRL)-FIL-cross-linked enzyme aggregates (CLEAs) (5.51 U/mg protein) was 1.9 times that of CRL-CLEAs (2.86 U/mg protein) and 1.4 times that of CRL-bovine serum albumin (BSA)-CLEAs (3.98 U/mg protein)
The organic tolerance test showed that the tolerance of CRL-FIL-CLEAs to isopropanol was better than other immobilized lipase
Summary
Lipase (EC 3.1.1.3) is a very unique biocatalyst with interface activation mechanism [1]. The low stability limited the application of free CRL in catalytic reactions. The lipase molecules are connected by cross-linking agent, the reusability could be improved. The particles of carrier-free immobilized lipase are generally smaller, and the dispersion in the solvent is more uniform. CLECs have excellent operational stability, the high purity requirements of crystallase lead to enhanced costs [7]. CLEAs do not require high-purity lipases, the preliminary purification could be integrated with immobilization process simultaneously. By adding more functional molecules with amino groups (for example: bovine serum albumin) in lipase cross-linking process, the loss of lipase activity can be reduced. Using functional molecules with amino groups to modify the surface of the lipase could affect the opening degree of the "lid" and speed up the substrate to enter the active center. This study is expected to enhance the activity and stability of CRL low-costly
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