Screening of Aspergillus niger 03214 Strain Producing Phytase and Sequence Analysis of Its Phytase phyA Gene

A total of 102 phytase-producing microorganisms were screened from the soil. The most active fungal isolate of them, designated 03214, was identified as Aspergillus niger. The optimal pH values for the activity of the phytase produced by Aspergillus niger 03214 were found to be in pH 1.5 to 2.5 and the optimal reaction temperature of the phytase for its activity was about 50 ℃. Cultivated with a shaking method, the phytase of the strain was produced at 345U/mL fermented liquid. The phyA gene encoding phytase was cloned from Aspergillus niger 03214 by PCR. Nucleotide sequence analysis of the phyA gene revealed that the coding region was 1 506 bp in length included with a 102 bp intron, and encoded a peptide of 467 amino acid residues. A signal peptide encoding 19 amino acids was found at the 5'end. There were ten potential N-glycosylation sites in the phytase.