Phytase activity of anaerobic ruminal bacteria

Phytase catalyses the release of phosphate from phytate (myo-inositol hexakisphosphate), the predominant form of phosphorus in cereal grains, oilseeds and legumes. The presence of phytase activity was investigated in 334 strains of 22 species of obligately anaerobic ruminal bacteria. Measurable activities were demonstrated in strains of Selenomonas ruminantium, Megasphaera elsdenii, Prevotella ruminicola, Mitsuokella multiacidus and Treponema spp. Strains isolated from fermentations with cereal grains proved to have high activity, and activity was particularly prevalent in S. ruminantium, with over 96% of the tested strains being positive. The measured phytase activity was found exclusively associated with the bacterial cells and was produced in the presence of approximately 14 mM phosphate. The most highly active strains were all S. ruminantium, with the exception of the one Mitsuokella multiacidus strain examined. Phytase activity varied greatly among positive strains but activities as high as 703 nmol phosphate released (ml culture)-1 were measured for a S. ruminantium strain and 387 nmol phosphate released (ml culture)-1 for the Mitsuokella multiacidus strain.