Immobilization on magnetic nanoparticles of the recombinant trehalose synthase from Deinococcus geothermalis

Abstract

In our study the gene encoding trehalose synthase from Deinococcus geothermalis was cloned and overexpressed in Escherichia coli Rosetta (DE3)pLysS. Wild-type trehalose synthase has been purified from host protein after cell disruption and precipitation at 20% ammonium sulphate saturation. Recombinant trehalose synthase was immobilized onto glutaraldehyde activated silanized magnetic ferrous-ferric oxide by using covalent binding method. The morphology and surface of the obtained particles were characterized using SEM. These images show that all samples have a particle size below 30nm. The obtained immobilized preparation has specific activity of 0.134U/g support when measured at 40°C using maltose as substrate. Immobilization process was almost fully completed after 30min of the reaction at 30°C. The highest immobilization yield of the enzyme was achieved at glutaraldehyde concentration of 10mM. No significant differences in optimal pH and temperature were observed upon immobilization. The immobilized trehalose synthase exhibited mass transfer limitation, which is reflected by higher KM and activation energy values. In addition, immobilized trehalose synthase was easily separated from the reaction medium by an external magnetic field and retained 82% of its initial activity after successive twelve repeated batches reaction.