Screening of a Protease-Producing Strain Acinetobacter calcoaceticus and Characterization of the Enzyme

Abstract:

A strain E9 to produce protease efficiently was screened from environmental samples with skimmed milk as carbon and nitrogen sources and was identified to be a strain of Acinetobacter calcoaceticus based on biochemical and physiological properties as well as the 16S rDNA gene sequencing. Its optimal fermentation conditions were found to be temperature 35 ℃，initial pH 6.0，inoculation 4% and culture time of 30 h，and the optimal fermentation medium contained 10 g/L of sucrose，15 g/L of beef extract，7 g/L of K2HPO4·3H2O，3 g/L of KH2PO4 and 1 g/L of MgCl2·6H2O. The resulting protease showed high activity and superior stability with moderate temperature and neutral pH values，and its kinetic parameters Km and Vmax were determined to be 7.067 mg/mL and 966.7 μg/（mL·min），respectively.