Aspergillus niger pH 2.1 optimum acid phosphatase with high affinity for phytate

An extracellular acid phosphatase isolated from the culture of a wild strain Aspergillus niger, producing the dephosphorylating 3-phytase, was obtained in a homogeneous form by sequential application of ultrafiltration through PS 50 membrane, gel filtration on Sephadex G-100 and ion exchange chromatogra- phy on DEAE-Sepharose CL 6B and CM-Sepharose CL 6B. The enzyme showed a maximum catalytic value in a strongly acidic range (pH 2.0-2.4) with pHopt 2.1 and topt 66 °C. The acid phosphatase showed a wide substrate specificity and a high affinity for sodium phytate, 2.5× higher than with 4-nitrophenyl phosphate. This property of the acid phosphatase demonstrated that it is a potent 3-phytase at pH 2.1 and is of great sig- nificance for a practical application of the dephosphorylating complex - its addition to the diets of mono- gastric animals in view of the low pH values in the digestive tract.