Physiological factors affecting the metabolic potential of recombinant E.coli in foreign protein production

Abstract

In order to investigate the metabolic potential of recombinant E. coli in the foreign protein production, the synthesis fo lipase and the lymphotoxin was induced in E. coli under different physiological states. The effect of metabolic inhibitors on foreign protein production were studied. The period of the lymphotoxin synthesis in E. coli MM294 was about 2 hours and constant independent of the degree of glucose uptake inhibition by $\alpha$-methyl glucose. When menadione and iodoacetate were used as metabolic inhibitors, the periods of lipase and lymphotoxin synthesis in E. coli was decreased to less than 2 hours. The specific oxygen uptake rate in E. coli MM294 was immediately decreased after the induction of lymphotoxin and reached the same level as a maintenance energy level of E. coli in 2 hours after induction. It seemed that some more general metabolic event occurs to halt protein synthesis within about 2 hours after the induction of foreign protein synthesis. Thus, the maximum level of foreign protein in the cell was determined by the rate of foreign protein synthesis within the limited period of about 2 hours. The period of lymphotoxin synthesis in E. coli MM294 at $25\,^\circ\!C$ was increased to 7 hours after induction. When the lymphotoxin synthesis was induced in different times after the shift of culture temperature to $18\,^\circ\!C$, the production pattern of lymphotoxin was different according to the time of induction. The synthesis of lipase and lymphotoxin by induction in carbon starved cell could be maintained for more than 5 hours after the onset of starvation.