Phytase

Description

Phytases are phosphatases able to hydrolyze O–P bonds in phytic acid liberating inorganic phosphate. Phytases can be grouped according to the attack on the hexaphosphoric ester into 3-phytase (myo-inositol-hexakisphosphate 3-phosphohydrolase, EC 3.1.3.8) as well as 4-phytase (myo-inositol-hexakisphosphate 4- phosphohydrolase, EC 3.1.3.26), releasing the phosphate at the corresponding position at the inositol ring.
Phytic acid is used by plants to store different type of anions (Cu2+, Fe2+/3+, Ca2+, Mg2+, etc.). The resulting salts are known as phytates. Nonruminant animals do not have the enzymatic ability to hydrolyze phytates; therefore, phosphate and minerals are not absorbed, but rather they pass through the intestinal tract undigested. The addition of phytases to food and feed does therefore enhance the availability of phosphate and minerals bound in phytates. More than 20 years ago, the first commercial phytase product for feed, Natuphos, was released. Nowadays, several other phytase products are available on the market for the improvement of animal feed, such as Ronozyme from Novozymes and Finase from AB Enzymes. The range of applications in nonruminant feed is large, as discussed in several reviews on the usage of phytases in the fodder of pigs, poultry, and fish. Additionally, phytase might also be used in food for the improvement of the nutritional value of cereal food products by degrading phytate.
Commercial recombinant production of phytases occurs generally, if not exclusively, in ascomycetes, whereas the phytase genes originate from different phyla: bacteria, ascomycetes, and basidiomycetes (Peniophora lycii). Industrial production takes place in liquid media in stirred bioreactors on a 6 9 120 m3 scale. In addition, the cultivation of phytase producing filamentous fungi in solid-state or solid-substrate fermentation systems has also been studied, but it lacks industrial adaptability. Another opportunity for the production of phytases is the usage of transgenic plants, such as maize, rice, soybean, and wheat.