Heterologous expression and optimization using experimental designs allowed highly efficient production of the PHY US417 phytase in Bacillus subtilis 168

Phytate/phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate; IP6) is the major storage form of phosphorus (P) in cereals, legumes and oilseeds accounting for ~60-90% of the total P content in plants (Rao et al. 2009). It is considered as an anti-nutrient factor since it forms insoluble complexes with nutritionally important ions such as Ca2+, Zn2+, Mg2+, Fe2+, and Mn2+. Phytases catalyze the release of phosphate from phytate, thereby generating less-phosphorylated myo-inositol derivatives (Li et al. 2010;Rao et al. 2009). Monogastric animals, such as poultry, swine and fish, cannot utilize phytate-P because their gastrointestinal tracts are deficient in phytase activity (Baruah et al. 2005). Supplementation of feeds destined to these animals with inorganic P is not only expensive, but also potentially polluting and non-sustainable. Indeed, in areas of extensive animal production, the supplementation of animal feed with inorganic P has led to increased manure P excretion levels and high soil P concentrations causing non-point pollution to surface and ground waters (Boesch et al. 2001). During the last two decades, exogenous phytases have been used as feed additives for monogastrics. Their inclusion into P-deficient diets is associated with substantial increases in total tract degradation of phytate-P and thus in the improvement of P bioavailability and growth performances (Li et al. 2010;Rao et al. 2009). Phytase also helps in the enhancement of vital minerals, amino acids and dietary carotenoids availability. Phytases are thus viewed as environmental-friendly products, which can reduce manure P excretion in intensive livestock management areas by limiting addition of exogenous P (Emiola et al. 2009;Jendza and Adeola 2009).Although most of the commercially available phytases are fungal histidine acid phytases derived from Aspergillus species, bacterial phytases from the genus Bacillus are an alternative because of their high natural thermal stability, neutral pH o