Manipulation of plasmid stability through optimization of fermentation conditions

Plasmid stability is a key measure of cell line fidelity in recombinant bacterial fermentation processes. Process stresses upon a cell has been shown to lead to loss in plasmid stability. In early study, a 1-L fed-batch process using an E. coli cell line resulted in plasmid stability measurements that varied between 50-and-80% 12 hours following induction with isopropyl β-D-1-thiogalactopyranoside (IPTG). In order to investigate this issue, a definitive screen DOE of six process factors (pH, DO, temperature, IPTG concentration, feed-1 rate, feed-2 rate) was undertaken to understand how crucially each process condition affected plasmid stability. The predicted outcomes from the DOE were confirmed with follow-up experiments and resulted in plasmid stabilities above desired thresholds.