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The Study of Function of Lipase Biocatalyst Immobilized on Silica Nanoparticles Used for Biodiesel Production

Kalantari, Mohammad | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42493 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Kazemini, Mohammad; Arpanaei, Ayyoob; Tabandeh, Fatemeh
  7. Abstract:
  8. Superparamagnetic core/shell nonporous (S1) and core/shell/shell mesoporous (S2 and S3) nanocomposite magnetite/silica particles with a magnetite cluster core of 130±30 nm, a nonporous silica shell of 90±10 nm thickness, and a mesoporous silica shell of 70±15 nm thickness were prepared thorough a simple method. Mesoporous particles were prepared with two BJH pore sizes (2.44 for S2 and 3.76 nm for S3 particles, respectively). The fabricated S1, S2 and S3 particles present high saturation magnetization values of 20, 13 and 17 emu/g, respectively. As a biological application, the lipase from Pseudomonas cepacia was successfully immobilized onto the amino-functionalized nanocomposite particles with glutaraldehyde and the effect of pore size of the carrier on the properties of the immobilized lipases was studied. The results showed that the enzyme loading of mesoprous structures (S2 and S3) are higher than that for nonporous particles (S1). The activity assay revealed that immobilized lipases retain about 90% of he free enzyme’s activity. Besides, the optimal temperature and pH for activity of lipases increased after immobilization. Furthermore, thermal stability of immobilized enzymes was much more enhanced comparing to the free ones, regardless of the carrier pore size. In addition, kinetic parameters of free and immobilized lipases were estimated. These results indicated that the Km values of immobilized lipases were considerably higher than free ones. But, the Vmax for enzyme molecules immobilized on particles was lower comparing to the free enzyme molecules. Finally, the immobilized lipases were used as the biocatalyst for transesterification reaction to convert the soybean oil to biodiesel. In examining the reusability, the immobilized lipases retained more than 55% of their initial conversion capability after 5 times reused which reveals high stability and recyclability of immobilized lipases in the transesterification of soybean oil
  9. Keywords:
  10. Mesoporous Silica ; Nonporous Silica ; Biodiesel ; Core-Shell Structure ; Enzyme Stabilization ; Lipase Enzyme ; Magnetite Nanoparticle

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