THE EFFECTS OF MIXING ON BIOPROCESSES - CONCENTRATION DISTRIBUTIONS AND MECHANICAL SHEAR-STRESS

The effects of mixing on batch alcohol fermentation of diluted solutio ns of starch hydrolysate is studied. The results of a limited number o f samples simultaneously drawn at different locations in the reactor a nd after different reaction times have been used in a simple mathemati cal model to provide a, picture of the concentration distributions wit hin the reaction environment. The optimal mixing conditions for the fe rmentation are met at rotation speeds between 1.7 and 5.0 s-1, while t he broth homogeneity obviously increases indefinitely with increasing this parameter. This suggests. the existence of a shear stress for the biomass, whose effect increases. with the application time and seems to affect the process mainly at the end of the fermentation.