SUMMARY: A theoretical treatment of continuous culture is given, which allows quantitative prediction of the steady-state concentrations of bacteria and substrate in the culture, and how these may be expected to vary with change of medium, concentration and flow-rate. The layout and operation of a small pilot plant for the continuous culture of bacteria are described. This plant has been operated continuously for periods of up to 4 months without breakdown or contamination of the culture. No alterations in the properties of the organisms studied have occurred during such periods of continuous culture. Results are given of a series of experiments on the continuous culture of Aerobacter cloacae in a chemically defined medium, designed to allow quantitative comparison with the results predicted by the theory. The relative advantages of batch and continuous culture as production processes are discussed, and it is concluded that continuous culture may usually be expected to show a five to tenfold increase in output as compared with a batch process.The continuous culture of micro-organisms is a technique of increasing importance in microbiology. The essential feature of this technique is that microbial growth in a continuous culture takes place under steady-state conditions; that is, growth occurs a t a constant rate and in a constant environment. Such factors as pH value, concentrations of nutrients, metabolic products and oxygen, which inevitably change during the ' growth cycle ' of a batch culture, are all maintained constant in a continuous culture; moreover, they may be independently controlled by the experimenter. These features of the continuous culture technique make it a valuable research tool, while it offers many advantages, in the form of more economical production techniques, to the industrial microbiologist. Nevertheless, the technique has so far been comparatively little used. (The review of Novick (1955) lists nearly all the work on the subject that has yet appeared.) The reasons for this relative neglect are, we believe, twofold.The first reason is the lack of a generally accepted theoretical background. Continuous culture presents theoretical problems of an essentially kinetic nature which must be solved before the technique can be intelligently applied.

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SummaryThis paper describes the design and operation of an industrial type culture system for the submerged growth of BHK 21 cells a t a volume of 30 1. Using a modified Eagle's medium and with the culture controlled at pH 7.4 f 0.05 and at a temperature of 35 f 0.25"C., the cells grew from 0.5 X lo6 to about 2.5 X lo6 viable celLs/ml. in 50 hr. a t stirrer speeds of 330 and 460 rpm. The significance of certain aspects of design and operation of a culture system of this type is discussed.

SUMMARY: The design and construction of a continuous culture apparatus with a 2 1. culture vessel are described. Aeration is achieved by means of a mechanical stirrer and injected air, automatic temperature and pH control are features of the apparatus, and foaming is controlled by adding antifoam through a manually operated valve. A high degree of agitation ensures that good mixing takes place. Accurate and easily variable control of the medium flow rate is obtained by means of the Mariotte bottle principle. The apparatus can be operated continuously with freedom from contamination for periods in excess of 1000 hr.

SUMMARY: The application of a radial mechanical shaft seal, and other improvements to a 2–3 1. capacity culture vessel, are described.

Present-day chemical and physical studies of the niicleic acid system of bacteria frequently call for qtiaiitities 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, a) 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 roli, 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 nlaximunl 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. I ,. .

SummaryEquipment for the sterilization of air by heat with capacities of 140 l./min., and 1700 l./min. respectively is described. An improved method for testing sterility is given.

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