MONITORING AND CONTROL OF RECOMBINANT PROTEIN-PRODUCTION

For better control of the production of a toxic product by recombinant Escherichia coli carrying three different types of multicopy plasmids, the total and viable cell concentration, total cell count (TCC), number of colony-forming units (CFU), plasmid copy numbers, intracellular enzyme activity and the concentrations of the cell metabolites in the cultivation medium were monitored. This was performed during the growth phase and after chemical induction with IPTG and temperature induction, respectively. Gene expression was carried out in a small stirred-tank reactor and in a 60-l tower loop reactor equipped with a draught tube. Cell concentration was determined with an in situ turbidometer, TCC by off-line counting, cell viability by culture fluorescence, CFU also by off-line counting, the concentration of metabolites with off-line and on-line liquid chromatography and with off-line and on-line flow-injection analysis (FIA) and intracellular enzyme concentrations by off-line and on-line FIA. The evaluated data allowed an improvement of the production process, and increases in cell concentration and volumetric and specific productivity.