Susceptibility of wheat and Aspergillus niger phytases to inactivation by gastrointestinal enzymes.

The activity of wheat and Aspergillus niger phytases was determined following preincubation for 60 min at 37 degrees C alone or in the presence of pepsin or pancreatin to examine their ability to survive in the gastrointestinal tract. At pH 3.5 both phytases were stable, but at pH 2.5 wheat phytase rapidly lost activity. Following preincubation at pH 3.5 in the presence of 5 mg of pepsin/mL, A. niger phytase retained 95% of its original activity, whereas only 70% of the wheat phytase activity was recovered. The stability of A. niger phytase in the presence of pepsin was the same at pH 2.5 as at pH 3.5. Results similar to those with pepsin at pH 3.5 were obtained following preincubation of the phytases in the presence of pancreatin at pH 6.0.