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Effects of post-induction feed strategies on secretory production of recombinant streptokinase in Escherichia coli
Institution:1. Division of Molecular Medicine and Virology, Department of Biomedical and Clinical Sciences, Linköping University, 581 85 Linköping, Sweden;2. Noviral Sweden AB, Västmannagatan 3, 111 24 Stockholm, Sweden;3. Division of Clinical Microbiology, Linköping University Hospital, 581 85 Linköping, Sweden;4. Division of Infectious Diseases, Department of Medicine Solna, Karolinska Institute, 171 76 Stockholm, Sweden
Abstract:The effects of post-induction nutrient feed rates, on recombinant streptokinase production in fed-batch processes, were investigated using various feed profiles. Recombinant streptokinase was produced using a secretory expression system and was induced by a temperature up-shift, using a temperature-sensitive λPL promoter. The specific growth rates decreased sharply upon induction of recombinant protein expression, thus necessitating a variable feed strategy in the post-induction phase. The various feed profiles employed in the post-induction phase included constant feed rates, linearly increasing feed rate and exponentially varying feed rates. Significant differences were obtained in the specific activity of streptokinase produced in these fed-batch processes. A maximum activity per unit biomass of 4.96 × 106 and 4.43 × 106 IU/g DCW was achieved for exponentially decreasing feed and linearly increasing feed, respectively. The decrease in specific growth rate during the post-induction phase was also less pronounced in these cases in comparison to other fed-batch experiments. It was observed that streptokinase productivity is governed by the nutrient feed rate per unit biomass at a critical juncture after induction. The highest activity per unit biomass was obtained when the nutrient feed rate per unit biomass was around 0.7–0.8 g glucose (g DCW)?1 h?1, between 2 and 4 h after induction.
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