Production, purification and properties of microbial phytases

Phytases (myo-inositol hexakisphosphate phosphohydrolase, EC 3.1.3.8) catal yse the release of phosphate From phytate (mycoinositol hexakiphosphate). S everal cereal grains, legumes and oilseeds, etc., store phosphorus as phyta te. Environmental pollution due to the high-phosphate manure, resulting in the accumulation of P at various locations has raised serious concerns. Phy tases appear of significant value in effectively controlling P pollution. T hey can be produced from a host of sources including plants, animals and mi cro-organisms. Microbial sources, however, are promising for their commerci al exploitations. Strains of Aspergillus sp., chiefly A. ficuum and A. nige r have most commonly been employed for industrial purposes. Phytases are co nsidered as a monomeric protein, generally possessing a molecular weight be tween 40 and 100 kDa. They show broad substrate specificity and have genera lly pH and temperature optima around 4.5-6.0 and 45-60 degreesC. The crysta l structure of phytase has been determined at 2.5 Angstrom resolution. Immo bilization of phytase has been found to enhance its thermostability. This a rticle reviews recent trends on the production, purification and properties of microbial phytases. (C) 2001 Elsevier Science Ltd. All rights reserved.