Investigation of Yeast Invertase Immobilization onto Cupric Ion-Chelated, Porous, and Biocompatible Poly(Hydroxyethyl Methacrylate-n-Vinyl Imidazole) Microspheres

Sari M. M.

APPLIED BIOCHEMISTRY AND BIOTECHNOLOGY, vol.163, no.8, pp.1020-1037, 2011 (Peer-Reviewed Journal) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 163 Issue: 8
  • Publication Date: 2011
  • Doi Number: 10.1007/s12010-010-9106-x
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.1020-1037


Cupric ion-chelated poly(hydroxyethyl methacrylate-n-vinyl imidazole) (poly(HEMA-VIM)) microspheres prepared by suspension polymerization were investigated as a specific adsorbent for immobilization of yeast invertase in a batch system. They were characterized by scanning electron microscopy, surface area, and pore size measurements. They have spherical shape and porous structure. The specific surface area of the p(HEMA-VIM) spheres was found to be 81.2 m(2)/g with a size range of 70-120 mu m in diameter, and the swelling ratio was 86.9%. Then, Cu(II) ion chelated on the microspheres (546 mu mol Cu(II)/g), and they were used in the invertase adsorption. Maximum invertase adsorption was 51.2 mg/g at pH 4.5. Cu(II) chelation increases the tendency from Freundlich-type to Langmuir-type adsorption model. The optimum activity for both free and adsorbed invertase was observed at pH 4.5. The optimum temperature for the poly(HEMA-VIM)/Cu(II)-invertase system was found to be at 55 A degrees C, 10 A degrees C higher than that of the free enzyme at 45 A degrees C. V (max) values were determined as 342 and 304 U/mg enzyme, for free and adsorbed invertase, respectively. K (m) values were found to be same for free and adsorbed invertase (20 mM). Thermal and pH stability and reusability of invertase increased with immobilization.