A NEW SCALE-UP METHOD BASED ON THE EFFECT OF VENTILATION ON AERATED FERMENTATION SYSTEMS

A new scale-up method based on the effect of ventilation on aerated fermentation systems was developed. The volatilization rate constant (kv) of the volatile compound was proposed as an index for showing quantitatively the effect of ventilation on the aerated fermentation systems. The kv value of a volatile compound 2-octanol, an inhibitor of cell growth, in jar fermentor was affected mainly by the air flow rate and to an extent by the agitation speed. In a scale-up of culture systems having a volatile growth inhibitor as a rate limiting factor, the need to consider both the oxygen transfer rate and the ventilation effect was demonstrated in a simple yeast model culture containing 2-octanol. It was shown quantitatively that an Erlenmeyer flask with a cotton plug had essentially no ventilation effect when compared to a jar fermentor. An aerated-flask having a forced-air system was therefore designed and a new method of scale-up from this flask to jar fermentor on the basis of the kv value was proposed. The usefulness of both the aerated-flask and this new scale-up method was demonstrated with the model yeast culture.