Purification and properties of a thermostable phytase from Bacillus sp. DS11

Bacillus species producing a thermostable phytase was isolated from the soil of a Korean cattle shed. An extracellular phytase from Bacillus sp. DS11 was purified to homogeneity by acetone precipitation and Phenyl-Sepharose, Resource S, and Superose 12 column chromatographies. Its molecular weight was estimated to be 44 kDa by SDS-polyacrylamide gel electrophoresis. Its optimum temperature for phytase activity was 70°C and about 50% of its original activity remained after incubation at 90°C for 10 min in the presence of 5 m m CaCl 2. Calcium ions were required for thermal stability. The optimum pH for enzyme activity was 7.0 and fairly stable from pH 4.0–8.0. The enzyme had an isoelectric point of 5.3. The K m value for phytate was 0.55 m m. Its activity was greatly inhibited by EDTA and metal ions such as Cd 2+ and Mn 2+. As for substrate specificity, it was very specific for phytate and had little or no activity on other phosphate esters. The enzyme efficiently hydrolyzed phytate in rice flour.