Batch Fermentation
Batch fermentation can be considered a closed culture system containing an initial limited amount of nutrient, which is inoculated with microorganisms to allow the fermentation of sugars to ethanol. In this traditional method, no ingredients are added during the fermentation process after inoculation, except possibly acid or alkali for pH control. In the batch fermentation, microorganism works in high substrate concentration initially and a high product concentration finally. Furthermore, the batch process is a multi-vessel process which allows flexible operation and easy control over the process. However, batch fermentation is a labor intensive process and is characterized by low productivity. For batch fermentation, elaborate preparatory procedures are needed because of the discontinuous start-up and shut-down operations. As a result, high labor costs are common in batch fermentation operations. These inherent disadvantages and the low productivity offered by the batch process have led many commercial operators to consider other fermentation methods.