Considerations on the use of phytase

Phytase (myo-inositol hexaphosphate phosphohydrolase) is an enzyme that is capable of catalysing the hydrolysis of phytate or phytic acid (phytate is a salt of phytic acid hexaphosphoinositol: C6H18O24P6 containing 28% phosphorus) to (inorganic) phosphate and lower phosphoric esters of myo-inositol. It releases phosphorus, making this available for absorption and utilization by monogastric animals and thereby reducing phosphorus excretion.

Phosphorus (P) consumed by animals is partly excreted in the manure. A major contributor to this is phytic acid, found in vegetable feed materials, which binds 60% - 80% of the total phosphorus present. Phytate-bound phosphorus is not available to monogastric animals, as they have insufficient intestinal enzymes to digest it effectively. Phytase is thus capable of releasing phytate-bound phosphorus and making it available to monogastrics. Commercial phytases are based on different genetically modified microbial strains, giving different levels of efficacy, and are available in several physical formulations.

Molecular structure of phytic acid (from Graf, 1986)