Functionalized κ-carrageenan/hyperbranched poly(amidoamine)for protease immobilization: Thermodynamics and stability studies

Int J Biol Macromol. 2020 Apr 1:148:1140-1155. doi: 10.1016/j.ijbiomac.2020.01.122. Epub 2020 Jan 15.

Abstract

Hyperbranched polyamidoamine (PAMAM) has a high density of surface amino groups. This feature was exploited in the surface modification of κ-carrageenan gel beads for successful protease immobilization. The optimum PAMAM pH was at 2.1 and 9.3. However, treatment of κ-carrageenan gel beads at the higher pH showed re-usability for more than seven successive times. As a result of central composite design optimization, the maximum immobilization yield was obtained by soaking 8 U for 24 h. The comparative thermodynamics studies showed an enhancement in the thermal stability at high temperature for the immobilized protease as well as increased half-life time from 24.06 min to 79.95 min. Also, the D-values increased from 165.03 min to 548.23 min for free and immobilized enzyme, respectively. Moreover, the enzyme stability enhancement for the immobilized protease catalyst was accompanied with a remarkable increase in the enthalpy and in the free energy. Immobilized protease onto Carr-PAMAM gel beads can retain 89% of its initial activity and lost only 11% after 8 weeks of storage at 4 °C. Furthermore, an effective removal of silver from used X-ray film by the immobilized protease was achieved for six repeated cycles.

Keywords: Covalent immobilization; Hyperbranched polymers; Protease; Thermodynamics; κ-Carrageenan.

MeSH terms

  • Carrageenan / chemistry*
  • Endopeptidases / chemistry*
  • Enzyme Stability
  • Enzymes, Immobilized*
  • Hydrogen-Ion Concentration
  • Polyamines / chemistry*
  • Spectroscopy, Fourier Transform Infrared
  • Temperature
  • Thermodynamics

Substances

  • Enzymes, Immobilized
  • Poly(amidoamine)
  • Polyamines
  • Carrageenan
  • Endopeptidases