5-55: Optimization of extracellular catalase production from Aspergillus phoenicis K30 by Plackett-Burman design and linear regression using date flour as single carbon source and purification of the enzyme

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 optimisation was performed. To select the factors affecting the production, nine active variables (factors) were analyzed by Plackett-Burman design consisting of 12 experiments. Each variable was tested at two levels, a higher and a lower level. The calculation of the effect of each variable and the establishment of a correlation between the response of enzyme activity and variables, have revealed that the link is a multiple regression form. The optimization was carried out through a simplex algorithm. The amount of extracellular catalase produced by the strain in the optimised medium was about four times higher than that obtained in nonoptimised 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 was 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 dimer. The isoelectric point of the protein was found to be 5 ± 0.1 as determined with a Pharmacia Phast-system