Now showing 1 - 2 of 2
  • Publication
    Effect of organic solvents on the activity and stability of halophilic alcohol dehydrogenase (ADH2) from Haloferax volcanii
    (Springer, 2013-01-01) ;
    The effect of various organic solvents on the catalytic activity, stability and substrate specificity of alchohol dehydrogenase from Haloferax volcanii (HvADH2) was evaluated. The HvADH2 showed remarkable stability and catalysed the reaction in aqueous–organic medium containing dimethyl sulfoxide (DMSO) and methanol (MeOH). Tetrahydrofuran and acetonitrile were also investigated and adversely affected the stability of the enzyme. High concentration of salt, essential to maintain the enzymatic activity and structural integrity of the halophilic enzyme under standard conditions may be partially replaced by DMSO and MeOH. The presence of organic solvents did not induce gross changes in substrate specificity. DMSO offered a protective effect for the stability of the enzyme at nonoptimal pHs such as 6 and 10. Salt and solvent effects on the HvADH2 conformation and folding were examined through fluorescence spectroscopy. The fluorescence findings were consistent with the activity and stability results and corroborated the denaturing properties of some solvents. The intrinsic tolerance of this enzyme to organic solvent makes it highly attractive to industry.
    Scopus© Citations 36  381
  • Publication
    Covalent immobilization of alcohol dehydrogenase (ADH2) from Haloferax volcanii: how to maximize activity and optimize performance of halophilic enzymes
    Alcohol dehydrogenase from halophilic archaeon Haloferax volcanii (HvADH2) was successfully covalently immobilized on metal-derivatized epoxy Sepabeads. The immobilization conditions were optimized by investigating several parameters that affect the halophilic enzyme-support interaction. The highest immobilization efficiency (100%) and retention activity (60%) were achieved after 48 h of incubation of the enzyme with Ni-epoxy Sepaeads support in 100 mM Tris-HCl buffer, pH 8, containing 3 M KCl at 5 ◦C. No significant stabilization was observed after blocking the unreacted epoxy groups with commonly used hydrophilic agents. A significant increase in the stability of the immobilized enzyme was achieved by blocking the unreacted epoxy groups with ethylamine. The immobilization process increased the enzyme stability, thermal activity and organic solvents tolerance when compared to its soluble counterpart, indicating that the immobilization enhances the structural and conformational stability. One step purification–immobilization of this enzyme has been carried out on metal chelate-epoxy Sepabeads, as an efficient method to obtain immobilized biocatalyst directly from bacterial extracts.
    Scopus© Citations 27  351