Pressurized culture of Escherichia coli for a high concentration.

The cultural conditions for obtaining a high concentration of Eschenchia coli K12 cells were investigated. A synthetic medium containing high concentrations of mineral salts was designed so as to support a high rate of cellular growth and the accumulation of a high cell concentration, without any additional feeding of inorganic nutrients, but with feeding of solid glucose. The pasteurization of the above mentioned medium at 65°C was found to be advantageous for the cellular growth since usual sterilization at 121°C caused denaturation of the medium, which was inhibitory for cellular growth. The accumulation of acetate, a well-known inhibitory product for the growth of E. coli, increased as the dissolved oxygen (DO) concentration decreased. When the DO concentration was maintained at the optimum value of 6.5ppm throughout the cultivation by pressurizing the culture system with oxygen gas, 134 g (dry basis)/l of cells was accumulated in 12 hr. The above culture conditions were applied to the cultivation of a recombinant E. coli strain transformed with pBR322trpAB, and 102g/1 of recombinant cells was obtained with a stably maintained recombinant plasmid in 9 hr under nonselective pressure.