| Vitamin E succinate is a more mature vitamin E derivative currently studied.Its chemical stability and many effects are improved compared to vitamin E.Not only can it make up for the shortcomings of vitamin E application,but also broaden the application field of vitamin E.At present,in developed countries such as Europe,America and Japan,the application of vitamin E succinate in health food is more common.Due to its better water solubility and stability,it is used in most nutritional supplements(tablets and hard capsules form)as vitamin E.At the same time,vitamin E succinate used in the food and pharmaceutical industries is mainly synthesized by enzymatic catalysis.In this article,Candida rugosa lipase(CRL),which has been optimized by the research group before,is taken as the research object.Improve to obtain immobilized lipase enzyme with high stability and high activity.It is applied to the enzymatic synthesis of vitamin E succinate,and the reaction conditions are optimized to increase the yield and reduce production costs.The main contents are as follows:(1)A new type of immobilized lipase based on the metal-organic framework compound ZIF-8 precursor molecule modification was constructed.First,CRL was chemically modified with 2-methylimidazole-4-carboxylic acid containing ZIF-8 precursor molecule,the modification rate was 16.3 %,and the modified CRL catalytic activity was 1.3 times higher than the free enzyme.Circular dichroism was used to characterize the modified CRL.The results showed that the modified CRL secondary structure was changed,and its ?-helix content increased to 18.9 %.The modified CRL was further used for in-situ synthesis of immobilized CRL composites(mCRL-ZIF-8).After fixation,the mCRL fixed by a covalent bond maintains similar activity as the CRL fixed by physical embedding.The study of its enzymatic properties showed that its storage stability,tolerance of organic solvents and reusability were improved.(2)Prepared a new type of lipase nanogel based on functional ionic liquid modification.First,the CRL was modified with ionic liquid,the modification rate was 19.5 %,and the catalytic activity of the modified CRL was 1.2 times that of free CRL.Circular dichroism spectrum results showed that the CRL molecule changed,and the CRL ?-helix content increased to 19.6 %.The modified CRL is further used to prepare lipase nanogels to obtain CRL-nanogels with excellent stability.CRL-nanogels' s pH and thermal stability,storage stability and resistanceto organic solvents have been improved.The organic solvent stability of CRL nanogel in ethyl acetate still retains 82.6 % of the catalytic activity,while free CRL only retains 14.8 %.After 7weeks of storage,free CRL retained only about 17.53 % of its catalytic activity.However,the activity of the CRL nanogel is almost unaffected,and the remaining activity is 97.26 %.(3)Optimized a new enzyme-catalyzed synthesis method of vitamin E succinate.CRL nanogels exhibited higher conversion rates.The DMSO with the lowest Log P value has the highest conversion rate.The process conditions(substrate molar ratio,enzyme concentration,reaction temperature and reaction time)were optimized.Under the optimal process conditions :substrate molar ratio 1:4,enzyme concentration 6 mg/mL,reaction temperature 55 °C and reaction time 15 h,the substrate conversion rate was 62.58 %. |
PDF Full Text Request