Production of an extracellular phytase from a thermophilic mould Humicola nigrescens in solid state fermentation and its application in dephytinization

In view of increasing demand of phytase, it is essential to produce and characterise cost-effective phytase from a new microbial source. Solid state fermentation (SSF) is the promising technology for commercial enzyme production with lower production cost. Among six isolates of thermophilic moulds, Humicola nigrescens was selected as a potent phytase producer on the basis of zone of hydrolysis. The mould produced phytase (48.28 U/g DMB) optimally in SSF using wheat bran at 45 °C, pH 5.0 after 2 days with substrate to moisture ratio of 1:2.5. Supplementation of wheat bran with sucrose and ammonium sulphate further enhanced phytase production. Phytase of H. nigrescens was partially purified 3.3-fold using ammonium sulphate precipitation. The partially purified enzyme was optimally active at pH 5.0 and 50 °C. The partially purified enzyme resulted in dephytinization of wheat and gram flour at 50 °C with the concomitant liberation of inorganic phosphate. Based on its biochemical properties and ability to dephytinize flours, phytase of H. nigrescens could be a potential candidate for food and feed industries.