تثبيت ‌‌آنزيم ليپاز بر روي ‌گرافن‌اكسايد پوشش داده شده با نانوذرات مغناطيسي نيكل فريت و كاربرد آن براي توليد بيوديزل از ليپيد ريزجلبك سندسموس ابليكوس

چكيده انگليسي :

Lipase Immobilization on the Graphene Oxide Coated with Nickel Ferrite Magnetic Nanoparticles and its Utilization in Biodiesel Production from lipid of Microalga Scenedesmus obliquus Fatemeh Aghabeigi f aghabeigi@ce iut ac ir Date of Submission Jul 2 2019 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Hamid Ziloui hzilouei@cc iut ac ir Mehdi Bazarganipour Bazarganipour@cc iut ac irAbstract According to the environmental limits and issues of fossil fuels which are also non renewable using alternativeenergy resources has become increasingly important To replace fossil fuels the increase in biodiesel productionas a biofuel has made us to pay more attention to the production process optimization so that not only it is capableof producing in large quantities but also has a simple and clean production process and reduces waste productionto its lowest level The purpose of this study is to synthesize magnetic nanocomposites based on graphene oxidefor the lipase immobilization to produce biodiesel In that regard the graphene oxide sheets coated with nickelferrite magnetic nanoparticles NiFe2O4 GO and used for enzyme immobilization The VSM XR SEM EDSand FTIR analyses were performed to find and confirm features of the nanoparticles graphene oxide andsynthesized magnetic nanocomposite and it was shown that nanoparticles are successfully synthesized andimmobilized to graphene oxide Furthermore lipase from candida rugosa was immobilized on the synthesizedbase The lipase immobilization process was studied using different enzyme concentrations 30 60 100 130 and160 g ml and different times 1 2 3 4 and 5 h The enzyme binding on this basis and the immobilized enzyme sactivity level were respectively studied by Bradford protein assay and the p nitrophenyl laurate p NPL hydrolysis technique Based on the best response of the immobilization efficiency and the resulted enzymeactivity 100 g ml enzyme concentration and 2 h incubation time were selected as the optimal conditions for theimmobilization process Subsequently free and immobilized enzymatic activities at various pH values 6 6 5 7 7 5 8 were studied and the optimal pH values for immobilized and free enzymes was respectively determined7 5 and 7 Moreover the activity of free and immobilized enzymes at various temperatures 20 30 35 40 50 C were studied and the optimal values for free and immobilized enzymes was respectively determined 35 and 40 C To evaluate thermal resistance and pH stability of free and immobilized enzymes they were also studied attemperatures of 30 40 50 and 60 C and pH values of 6 6 5 7 7 5 8 and 9 The results revealed that incomparison to free enzyme immobilized enzyme is more resistant so that at the temperature of 60 C it couldretain 70 of its initial activity and lost only 20 of it at pH of 9 Kinetics parameters were calculated studyingenzymatic activities value at various concentrations of p NPL substrate The values of Vmax for free andimmobilized enzymes were respectively calculated 12 and 6 54 U mg and the values of Km evaluated 0 61 and 0 7mM The immobilized enzyme after each p NPL substrate hydrolysis was recycled and reused by an externalmagnet so that after 6 cycles of hydrolysis it retained 47 of its initial activity which demonstrates the reusabilityand resistance of immobilized lipase Furthermore due to the numerus abilities for biodiesel production Scenedesmus obliquus the microalga was chosen and cultivated To increase the microalga lipid scientists haveused the two stage cultivation method and nitrogen deficiency By applying this method and cultivationconditions aeration with 3 CO2 under a photoperiod of 16 8 h light dark cycle at light intensity of 25 molephotons m2 s there was an increase in the value of microalga lipid from 11 5 to 18 At the end of the process after extracting microalgae lipid free and immobilized lipases were used as biocatalyst for biodiesel production

آقابيگي، فاطمه

تثبيت ‌‌آنزيم ليپاز بر روي ‌گرافن‌اكسايد پوشش داده شده با نانوذرات مغناطيسي نيكل فريت و كاربرد آن براي توليد بيوديزل از ليپيد ريزجلبك سندسموس ابليكوس

گرافن‌اكسايد , تثبيت آنزيم , ليپاز , نانوذرات مغناطيسي , نيكل فريت , بيوديزل , ريزجلبك , سندسموس ابليكوس