Study on the Aspergillus niger N25 Strain Producing Phytase and its Phytase Reaction Conditions

In this study, Aspergillus niger N25 ( A niger N25) highly-secreting phytase was isolated from soiland botanic seeds in P R China It was cultivated in corn,rice-meal and bran semi-synthesized culture mediums and one synthesized culture mediums producing phytase activity were 515 9nmol/ml·min,420 9nmol/ml·min,450 9 nmol/ml·min and 320nmol/ml·min,respectively,which indicated corn semi-synthesized culture medium was the best medium for A niger N25 When A niger N25 was cultivated in corn semi-synthesized culture medium for different time,phytase activity reached the highest level at 96h The optimum pH of A niger N25 phytase is 2 6 and 4 6 This enzyme had a broad optimum temperature range from 30℃ to 96℃,and showed a good heat stability Additionally,the certain concentration of Ca 2+ ,Mg 2+ ,Mn 2+ ,Cr 2+ ,Li +,EDTA and high concentration of phosphate inhibited the enzyme activity,while 0 3 nmol/ml Fe 2+ ,1 0mmol/ml polyethylene glycol 10000 and low concertration of phosphate can improve A niger N25 phytase activity