Microbial aspects of fermentation process development

Aspects of fermentation dynamics are discussed, especially from the point of view of process development. Initial examples are from laboratory work in continuous culture. After this the economic and dynamic aspects of protein production by continuous culture are reviewed. In the last part the optimisation of the pencillin fermentation is considered, based on the use of a model which predicts yields, with a fermentation limited by the rate of oxygen transfer to the culture, when penicillin production falls at low growth-rates. A process involving a sugar feed is considered, the main factors being the concentration of nitrogen in the medium, which governs initial cell production, and sugar feed rate which maintains further growth. The model predicts high yields over a wide variety of conditions. This indicates the difficulty of a pilot-plant optimisation programme, when the maximum yield point is not critical. Other factors in the fermentation are also discussed.