Screening of phytase producing strain and optimization of fermentation conditions

A phytase-producing strain was isolated and identified as Aspergullus niger FZ41. Liquid fermentation was investigated and the optimal fermentation medium obtained. A 500 mL flask filled with 50 mL inoculums with an initial pH of 6.0 was used in the inoculation. The relative percents of ingredients of fermentation medium were: starch 4%, NH₄NO₃ 0.08%, KCl 0.05%, MgSO₄·7H₂ 0.05%, FeSO₄·7H₂ 0.003%, MnSO₄·7H₂ 0.003%. The age of the inoculums was 36 h, with initial medium pH 6.0 and an inoculation dose of 5%. Extracellular phytase production was 219 U·mL^{-1 under fermentation conditions of 30 ℃ at 220 r·min-1 for 84 h.}