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

Bacillus species producing a thermostable phrase,I ns 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 14 kDa by SDS-polyacrylamine gel electrophoresis. Its optimum temperature for phytase activity was 70 degrees C and about 50% of its original activity remained after incubation at 90 degrees C for 10 min in the presence of 5 mM CaCl2. 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 mM. Its activity was greatly inhibited by EDTA and metal ions such as Cd2+ and Mn2+. 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. (C) 1998 Elsevier Science Inc.