| The catalytic performance of Candida sp.99-125 lipase and its immobilized lipase and other commercial lipases(lipase AS "Amano"and lipase PS "Amano" SD)or immobilized lipases(lipozyme TLIM,Novo 435,Novo 40086 and Novo RMIM)were studied at different temperatures.The main contents are as follows:1.The magnetic Fe3O4 nanoparticles were synthesized via a solvothermal method.The surface of the Fe3O4 nanoparticles was modified by epoxy chloropropane,and then the Candida sp.99-125 lipase was immobilized by covalent-adsorption-crosslinking method,namely FCACL.The study showed that amount of immobilized Candida sp.99-125 was 388.2 mg/g Fe3O4 nanoparticles.The esterification activity and reaction kinetics of Candida sp.99-125 and FCACL on lauric acid-n-octanol were studied at 40?.The results showed that the esterification activities of FCACL were 365.13 U/g and 88.01 U/g at 40? and 0? respectively,and that of Candida sp.99-125 was 219.42 U/g and 39.31 U/g at 40? and 0? respectively.The maximum reaction rate increased and michaelis constant decreased of the FCACL compared with the free lipase,indicating that the affinity of Candida sp.99-125 with lauric acid increased.The catalytic performances of FCACL under different temperatures were investigated.The results showed that the methyl ester rates of FCACL decreased with the temperature reduced,and the esterification rates declined with the long-chain fatty acid.The esterification rates of decanoic acid,lauric acid,myristic acid and palmitic acid were nearly 100%,and the esterification rate of stearic acid was more than 90%after 24 h at 4? or above;and even at 0?,the the esterification rates of decanoic acid and lauric acid were over 99%,while the esterification rates of myristic acid,palmitic acid and stearic acid decreased to 81.68%,68.82%and 62.40%,respectively.These indicated that the FCACL has a wide temperature adaptation range.Afer 7 bathces,the esterification rates of lauric acid with the FCACL catalyst reached 90.80%,71.09%,60.81%and 27.24%under 40?,20?,4? and 0?,respectively.Therefore,the FCACL had good reusability at 40?.2.The catalytic properties of several commercial free lipases,such as lipase AS "Amano" and lipase PS "Amano" SD,and immobilized lipases,such as lipozyme TLIM,Novo 435,Novo 40086 and Novo RMIM,were studied at different temperatures.The results showed that the esterification activities of lipase AS "Amano" and lipase PS "Amano"SD were relatively low,the highest esterification activity was 71.12 U/g and 64.77 U/g at the optimum temperature 30?,respectively,and the esterification activity at 0? was 43.5 U/g and 29.66 U/g,respectively.The esterification activities of the immobilized lipases Novo 435,Novo 40086,Novo RMIM and Lipozyme TLIM decreased with the decrease of temperature.The esterification activities of immobilized lipases novo 435,Novo 40086,Novo RMIM and lipozyme TLIM were 426.42 U/g,362.16 U/g,469.54 U/g and 384.85 U/g at 40? and 113.27 U/g,125.82 U/g,173.08 U/g and 75.24 U/g at 0?,respectively.The fatty acid methyl esters were performend by the above immobilized lipases at 4? and 0?,respectively.The results showed that the methyl esterification rates of decanoic acid,lauric acid,myristic acid and palmitic acid were 100%,and the methyl esterification rate of stearic acid was more than 90%at 24h.The above studies showed that the all immobilized lipases exhibited good esterification rates under a wide range of temperature,indicating that the esterification of immobilized lipases on wide range of temperature might are universal. |
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