الخلاصة:
Aspergillus phoenicis K30 is the selected mutant which produces an amount of extracellular catalase.
To amplify the extracellular catalase production by the strain, a fermentation optimization was
performed. To select the factors affecting the production, nine active variables (factors) consisting of 12
experiments were analyzed by Plackett-Burman design. Each variable was tested at two levels, a higher
and a lower level. The studies of the effect of each variable and the establishment of a correlation
between the response of enzyme activity and variables revealed that the link is a multiple linear
regression form. The optimization was carried out through a simplex algorithm. The amount of
extracellular catalase produced by the strain in the optimized medium was about four times higher than
that obtained in non optimized medium corresponding to 3820 mg/L of extracellular proteins including
59500 U/L of extracellular catalase activity after 96 h of fermentation. The steps of purification were
allowed to improve enzyme activity by 305-fold. From an analytical gel electrophoresis under native
conditions, an apparent molecular mass of 158 kDa was determined suggesting that the enzyme is a
homodimer. The isoelectric point of the protein was found to be 5 ± 0.1 as determined by a Pharmacia
Phast-system
