THE EFFECT OF REPEATED TEMPERATURE SHOCK ON BAKERS-YEAST

In a recycle system in which evaporation is used for ethanol recovery during fermentation, temperature changes of the broth in the loop will occur. These repeated temperature shocks may have an effect on the microbial ethanol production rate. In this study such repeated temperature changes were simulated in a recycle system with ethanol production by baker's yeast. The magnitude of the temperature change, as well as the time of exposure to this change were found to have an effect on the ethanol production rate. A temperature increase from 30-degrees-C in the fermentor to 35-degrees-C or more in the recycle loop led to a significantly lower ethanol concentration in the broth. This effect became negligible at a short exposure time of 18 s of the yeast to the higher temperature.