First of all, the following equipments should be installed inside and/or outside the fermentation tank so as to enhance the mixing effect. Second, control liquefaction and saccharification conditions properly so as to assure the appropriate granularity, liquefaction effects and material transport; and to overcome substrate inhibition. Third, select high activity yeast strains and use it in the right way Fourth, the fermentation process should be controlled at low fermentation temperature Fifth, work out a good plan of contamination control and a reasonable cleaning system Sixth, appropriate proportion of recycled supernatants. http://www.bolibio.com/blog/
You need to use high concentration of yeast in batch fermentation so that the whole process can work. The high concentrated yeast is good because it can be recycled. For more information, go to http://running_on_alcohol.tripod.com/id20.html.