Abstract

The phytase from Mitsuokella jalaludinii, a novel phytase-producing rumen bacterium, was purified 120-fold to near homogeneity and characterized. The phytase was completely cell-associated and about half of the enzyme activity was released when the bacterial cells were incubated with 1.5 mol/l KCl solution for 8 h. The optimum pH for phytase activity was in the range of 4.0 to 5.0 and the optimum temperature was 55 to 60°C. The phytase was stable at pH 4.0 to 7.0. It was highly specific to sodium phytate as the substrate, strongly inhibited by Cu²⁺, Zn²⁺, Fe²⁺and Fe³⁺, significantly stimulated by Ba²⁺ and slightly stimulated by Mn²⁺ and Ca²⁺. The metal ions chelating agents, namely trisodium citrate, potassium sodium tartrate and EDTA, did not show any inhibitory effect on the phytase activity of M. jalaludinii. The phytase was also not inhibited by sulfhydryl inhibitor, 2-mercaptoethanol, and a carboxyl inhibitor, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC).

Key words: Mitsuokella jalaludinii, bacterial phytase, rumen bacteria.