Enzymatic Properties of Phytase from Escherichia coli DH5α

Abstract

A Escherichia coli strain producing phytase named DH5α was chosen from four E. coli stains, the enzyme activity was 17.88 U/mL after fermented at 37°C for 2 days. The enzymatic properties of crude enzyme solution were studied. The optimal temperature was 55°C; optimal pH was 2.5 and 7.0, enzyme had certain resistance to heat and different pH conditions, 75% activity could be maintained when treated at 65°C for 30min, and 60% activity still remained when treated in the pH range of 2 to 9 for 30 min and 60 min. Resistance to KH 2 PO 4 of phytase was poor, low concentrations of KH 2 PO 4 (15mg/L) could inhibit the enzyme activity to below 40%; all kinds of metal ions had no significant activation or inhibition effect on enzyme, the enzyme had resistance to pepsin but no resistance to trypsin, after treated by trypsin for 30min, only 66.69% of the activity retained, while treated by pepsin , the activity could still maintain more than 90%.