Extracellular proteolytic activity of Deinococcus geothermalis

Abstract

Production of extracellular protease by extremophilic bacteria Deinococcus geothermalis cultivated in liquid media containing 0.1% (w/v) of peptone K, 0.1% yeast extract and 0.2% marine salt reached a maximum in 14 h of the cell growth at 45°C and pH 8.0. The enzyme was purified by a two-step procedure using fractionation by a graded ammonium sulphate precipitation technique and gel filtration on Sephadex G-100 column. Protease from D. geothermalis with a molecular mass of 24 kDa was active at 60°C and pH 9.0. The enzyme solution was stable for 1 h at 60°C and displayed about 60% of the initial activity after 1 h incubation at pH values 5.0 and 11. The phenylmethanesulfonyl fluoride (PMSF) at 1 mM concentration decreased proteolytic activity up to 27.4% of the initial value and it suggests that the enzyme is a serine protease. The activity was stimulated by Ca²⁺, Na⁺, Mg²⁺ and strongly inhibited by Hg²⁺, Cu²⁺, Zn²⁺ and Fe³⁺. Nonionic detergents like Triton X-100 and Tween 80 did not affect catalytic properties. It suggested that the enzyme produced by D. geothermalis could be used as a component of detergents.

Keywords: Deinococcus geothermalis, alkaline protease, detergents, thermostability

African Journal of Biotechnology Vol. 12(25), pp. 4020-4027