Phytase activity of Selenomonas ruminantium: a preliminary characterization

Obligately anaerobic ruminal bacteria have been found to possess phytase activity, in particular, Selenomonas ruminantium. The phytase activity of S. ruminantium JY35 was produced late in growth and required neither phytate for induction nor phosphate limitation for derepression. The activity was completely cell-associated with a significant fraction extractable by a magnesium chloride solution. Zymogram analysis suggested that the activity was the result of a single gene product of a monomeric nature and approximately 46 kDa in size. The phytase had a temperature optimum of 50–55 °C, but activity dropped off sharply at 60 °C. Phytase activity was optimal over the pH range of 4·0–5·5, and dependent on the nature of the buffer used. Activity was inhibited by citric acid buffer and by the addition of 5 mmol l−1 Fe2+, Fe3+, Cu2+, Zn2+ and Hg2+. The addition of 5 mmol l–1 Pb2+ to the enzyme assay appeared to enhance activity of the enzyme.