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.
Among six different isolates of thermophilic moulds, H. nigrescens was found to be potent phytase producer. This mould was amenable to grew well and secreted highest phytase titres in SSF. Optimisation of phytase production by “one variable at a time” approach increased the phytase production. The mould grew well in all agro-residues in SSF and secreted high enzyme titres using wheat bran at 45 °C and pH 5.0 after 2 days with a substrate to moisture ratio of 1:2.5. Addition of sucrose and ammonium sulphate further improved phytase production. Phytase of H. nigrescens was partially purified by ammonium sulphate precipitation with 3.33-fold purification. The enzyme was optimally active at pH 5.0 and 50 °C. The enzyme resulted in dephytinization of wheat and gram flour with concomitant release of inorganic phosphate and soluble protein. The enzyme being acid stable and thermostable could find application in dephytinization of food and feed ingredients for monogastric animals.