Effect of Preinduction Specific Growth Rate on Recombinant Alpha Consensus Interferon Synthesis in Escherichia coli

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Abstract
The effect of preinduction specific growth rate on the yield of recombinant alpha consensus interferon in Escherichia coli K-12 was investigated. The cells used in the investigation contain a temperature-sensitive, walkaway plasmid bearing an insert that codes for alpha consensus interferon. Transcription of the recombinant gene is controlled by a lambda repressor/pL promoter system. The lambda promoter is regulated by the temperature-sensitive gene cI857 at 30.degree. C, but at 42.degree. C the promoter is derepressed. The cells were grown under glucose-limited conditions in a chemostat at pH 7 and 30.degree. C. Once steady state was achieved, the vessel tempeature was raised to 42.degree. C and a fed-batch mode was initiated. Six dilution rates ranging from 0.025/h to 0.2/h were investigated. Cell dry weight, alpha consensus interferon content, glucose concentration, acetate concentration, and plasmid stability were measured. At each dilution rate, the expression level of alpha consensus interferon (g/g of cell dry wt) reached its maximum value approximately 3 h after induction. In addition, the expression level of alpha consensus interferon increased 4-fold as the dilution rate prior to induction is increased from 0.025/h to 0.2/h. Consequently, the expression of recombinant protein product of E. coli is dependent on the preinduction specific growth rate.