Purification and characterization of an extracellular halophilic and organic solvent-tolerant amylopullulanase from a haloarchaeon, Halorubrum sp. strain Ha25

Halophiles، especially haloarchaea are one of the most important groups of extremophiles. Halophilic hydrolases have been studied worldwide and have been considered for biotechnology and industrial technologies. This study is the first report in amylopullulanase production in halophilic microorganisms. Materials and method s: A halophilic archaeon، Halorubrum sp. strain Ha25، produced extracellular halophilic organic solvent-tolerant amylopullulanase. The enzyme was purified using ethanol precipitation and anion exchange chromatography method. Molecular mass of purified enzyme was determined by SDS–PAGE method. After purification، the enzyme was characterized. To study the effects of organic solvents in the stability of the enzyme، the enzyme solution was incubated in the presence of various organic compounds and then، residual enzyme activity was measured. Mode of action of the enzyme was determined by thin-layer chromatography. Molecular weight of the purified enzyme was estimated to be 140 kDa by SDS–PAGE method. Optimum temperature for amylolitic and pullulytic activities was 50 °C. Optimum pH for amylolitic activity was 7. 0 and for pullulytic activity was 7. 5. This enzyme was active over a wide range of concentrations (0-4. 5 M) of NaCl. The effect of organic solvents on the amylolitic and pullulytic activities showed that this enzyme was more stable in the presence of non-polar organic solvents than polar solvents. The enzyme solely hydrolyzed pullulan and soluble starch to glucose. Discussion and Halorubrum sp. strain Ha25 produces thermophilic and extremely halophilic amylopullulanase. The catalytic function under multi extreme condition of high temperature، high salinity، and low water activity might possess biotechnological and commercial values such as treatment waste solutions with starch residues، high salt content and solvents.