Octadecyl and sulfonyl modification of diatomite synergistically improved the immobilization efficiency of lipase and its application in the synthesis of pine sterol esters.

Phytosterols usually have to be esterified to various phytosterol esters to avoid their disadvantages of unsatisfactory solubility and low bioavailability. The enzymatic synthesis of phytosterol esters in a solvent-free system has advantages in terms of environmental friendliness, sustainability, and selectivity. However, the limitation of the low stability and recyclability of the lipase in the solvent-free system, which often requires a relatively high temperature to induce the viscosity, also increased the industrial production cost. In this context, a low-cost material, namely diatomite, was employed as the support in the immobilization of Candida rugosa lipase (CRL) due to its multiple modification sites. The Fe3 O4 was also then introduced to this system for quick and simple separation via the magnetic field. Moreover, to further enhance the immobilization efficiency of diatomite, a modification strategy which involved the octadecyl and sulfonyl group for regulating the hydrophobicity and interaction between the support and lipase was successfully developed. The optimization of the ratio of the modifiers suggested that the -SO3 H/C18 (1:1.5) performed best with an enzyme loading and enzyme activity of 84.8 mg·g-1 and 54 U·g-1 , respectively. Compared with free CRL, the thermal and storage stability of CRL@OSMD was significantly improved, which lays the foundation for the catalytic synthesis of phytosterol esters in solvent-free systems. Fortunately, a yield of 95.0% was achieved after optimizing the reaction conditions, and a yield of 70.0% can still be maintained after six cycles.

Ionic liquid modification reshapes the substrate pockets of lipase to boost its stability and activity in vitamin E succinate synthesis.

BACKGROUND: The relative low stability, reusability and activity of enzymes made the industrial production of vitamin E succinate (VES) can only be performed with complex processes and high cost using chemical methods. To address these issues, in the present study, an ionic liquids (ILs) modification strategy was developed to improve the activity and stability of lipases in VES synthesis. RESULTS: The results showed that the [1-butyl-3-methyl imidazole] [N-acetyl-l-proline] ILs modified Candida rugosa lipase (CRL) has the highest modification degree (48.28%), activity (774 U g-1 ), thermostability and solvent tolerance in three selected modifiers. Additionally, after reaction condition optimization, the highest yield of VES can be improved to 95.18% at 45 °C for 15 h, which was significantly improved compared to some previous studies. CONCLUSION: In the present study, a high-efficiency VES synthesis strategy was successfully developed via modification of lipase. Moreover, the mechanism by which ILs modification can enhance the activity and stability of lipase was investigated via both experimental and computational-aided methods. Molecular dynamics simulation suggested that ILs modification changed the geometry of Phe344 from flat to upright, which significantly reshaped and enhanced the size of substrate binding pocket of CRL. It is also agreement with our circular dichroism and fluorescence spectroscopy results, which suggested that the modification changed the secondary structure of CRL to a certain extent. The larger pocket also endowed the suitable binding pose of succinate, which made the hydrogen bonds between succinate and active site Ser209 become stronger, and thus improving the yield of VES. © 2023 Society of Chemical Industry.

Can vitamin E ester derivatives be excellent alternatives of vitamin E: state of art.

Vitamin E (VE) is a natural antioxidant which is widely used in the food fields, while the shortcomings of easy oxidative inactivation and poor water solubility limit its application. Vitamin E esters' (VEEs) derivatives, such as vitamin E acetate (VEA), are more stable and easier to be absorbed while have similar biological activities and physiological functions compared with VE. In this systematic review, the digestion, absorption and physiological function of VEEs were summarized. To promote their further industrial applications, the synthesis strategies of VEEs were also summarized in-depth. In particular, as a new generation of green solvents, ionic liquids (ILs) have been widely used in enzymatic reactions due to the stabilization and activation of enzymes. Their applications in enzymatic synthesis of VEEs were summarized and discussed. Finally, several future perspectives for developing more efficiency strategies of VEEs synthesis, such as enzyme engineering and design of novel ILs, were also discussed.

Study on the synthesis of pine sterol esters in solvent-free systems catalyzed by Candida rugosa lipase immobilized on hydrophobic macroporous resin.

BACKGROUND: Pine sterol ester is a type of novel food source nutrient with great advantages in lowering blood cholesterol levels, inhibiting tumors, preventing prostate enlargement, and regulating immunity. Macroporous resins with large specific surface area, stable structures, and various functional groups (epoxy, amino, and octadecyl groups) have been selected for immobilization of Candida rugosa lipase (CRL) to improve its stability and efficiency in the synthesis of pine sterol esters. A solvent-free strategy using oleic acid (substrate) as an esterification reaction medium is an important alternative for avoiding the use of organic solvents. RESULTS: The immobilization conditions of CRL immobilized on several types of commercial macroporous resins were optimized. Fortunately, by adsorption (hydrophobic interaction), a high immobilization efficiency of CRL was obtained using macroporous resins with hydrophobic octadecyl groups with an immobilization efficiency of 86.5%, enzyme loading of 138.5 mg g-1 and enzyme activity of 34.7 U g-1 . The results showed that a 95.1% yield could be obtained with a molar ratio of oleic acid to pine sterol of 5:1, an enzyme amount of 6.0 U g-1 (relative to pine sterol mass) at 50 °C for 48 h. CONCLUSION: The hydrophobic macroporous resin (ECR8806M) with a large specific surface area and abundant functional groups was used to achieve efficient immobilization of CRL. CRL@ECR8806M is an efficient catalyst for the synthesis of phytosterol esters and has the potential for further large-scale applications. Therefore, this simple, green, and low-cost strategy for lipase immobilization provides new possibilities for the high-efficiency production of pine sterol esters and other food source nutrients. © 2023 Society of Chemical Industry.