Effect of selected Hofmeister cations and anions on recombinant protease B solubility

Abstract

Cost of the total process of enzyme production at industrial scale depends mainly on its recovery and the recovery largely depends on the solubility of enzymes in solution. CaCl2 is usually used by Novozymes A/S, Denmark in the pre-treatment of Protease B UF concentrate on early downstream processing. Therefore, it has been tried in these experiments to find out alternative and cheaper cationic salt that could be used in the pre-treatment of Protease B UF concentrate in order to increase protein solubility in a cost-effective strategy of Protease B recovery and production at industrial scale. Beside these, the research work was designed to investigate whether the solubility of Protease B UF concentrate follows the order of the salts in the Hofmeister series against pH or not. Protease B, a recombinant proteolytic enzyme produced from genetically engineered Bacillus licheniformis was used in this study. Six different salts, five different cations (KCl, NaCl, LiCl, MgCl2 and CaCl2) and one anionic salt (Na2SO4) from the Hofmeister series were tested in these experiments. The highest protein solubility in Protease B UF concentrate was found in the presence of MgCl2 at 1.0 M concentration but the most significant and interesting effect on protein solubility was observed by CaCl2. Finally, a qualitative disagreement was observed in the presence of CaCl2.