Effect of culture conditions on the biosynthesis of Aspergillus niger phytase and acid phosphatase

The reduction of phytate content in plant feeds is advisable for increasing of their nutritional values. The dephosphorylation of phytates is believed to be mainly effected by phytase. A strain of Aspergillus niger shows a high potential for phytase production. In this study the possibilities to increase the enzyme production by alteration of the growth conditions of Aspergillus niger 307 are investigated. The effect of the type, age and quantity of the inoculum was established. The strain showed maximal productivity when about 50-day-old spores were used as inoculum and the augmentation of phytase and acid phosphatase activities was 3.29-fold and 2.17-fold, respectively. Two-fold increase of the phytase activity was observed when the inorganic phosphorus concentration in the media was 10 mg%. The highest level of acid phosphatase activity was produced at 17.5 mg% Pi. The unpurified phytase from Aspergillus niger 307 shows two pH optima-at 2.5 and 5.0 and temperature optimum (T-opt) is 56 and 58 degreesC, respectively. The pH optimum for acid phosphatase action is 2.1 and T-opt is 73 degreesC. (C) 2002 Elsevier Science Inc. All rights reserved.