Phytases release inorganic phosphorus from phytic acid or its salts, which are the major forms of organic phosphorus in plant-derived food and feed ingredients. These enzymes have been widely used in animal food/feed to improve nutritional value and to reduce phosphorus pollution in animal waste. The effectiveness of phytases as food/feed additive is dependent on their in vitro properties such as pH/temperature optima as well as stability and resistance to the action of proteases. Furthermore, all commercial phytases certified for use as feed additives are produced by recombinant microorganisms with similar properties. The microbial sources for phytases span from fungi to bacteria. The bacterial phytases differ from fungal phytases in that their pH optima range from acidic to alkaline, and they are Ca2+ dependent and highly substrate specific. Furthermore, bacterial phytases are resistant to the action of proteases found in the gastrointestinal tract of monogastric animals. Bacterial phytases have a molecular mass of 37-55 kDa, and are usually active within pH and temperature ranges of 4.5-8.5 and 25-70 degrees C, respectively. Bacterial phytases are used in food and feed industries for improving nutritional quality, bread making, promotion of plant growth promotion and reduction of phosphorus pollutant levels in the environment. (C) 2015 Elsevier Ltd. All rights reserved.