Production of Escherichia coli as a source of nucleic acids

Present‐day chemical and physical studies of the nucleic acid system of bacteria frequently call for quantities of cells which are beyond the capacity of traditional culture methods such as that of the shake flask. The case is therefore argued for an increased use of stirred deep cultures because a greater rate of output, at a higher cell concentration and with improved control of cultural conditions can be achieved. For the isolation of deoxyribonucleic acid and transfer ribonucleic acid, low growth‐rate cells should be the most prolific source: whereas for ribosomes, ribosomal ribonucleic acid and messenger ribonucleic acid, high growth cells should give bigger yields. It is concluded that the information is somewhat obscure on what are the best growth conditions for the production of the related‐enzymes. A batch method for producing low growth‐rate cells of Escherichia coli , in lots of 1 kg dry wt., is then described, followed by a continuous method for producing high growth‐rate cells, with an output of 3 kg of dry cells per day. Both cultures have been designed to give maximum yield of cells by promoting maximum assimilation of the carbon substrate. From the point of view of designing a culture, the section dealing with the continuous process discusses the rationale of medium formulation, the calculation of aeration requirements and briefly reviews earlier work on the kinetics of continuous culture.