Production of Glycerol from Corn by a Yeast Fermentation

This Phase II proposal and the recently completed Phase I project deal with a new process of production of glycerol from cornstarch by a yeast fermentation. There are two current industrial processes for glycerol. Chemical syntheses are no longer competitive. The second method involves recovering glycerol as a byproduct from soap and other fatty acid industries. It suffers from the decline of the main products and also the large and thus restrictive 7 to 1 main-products to byproduct ratio. The byproduct simply cannot grow much without upsetting the market supply-demand balance of the main-products. Phase I work has improved the glycerol fermentation to a peak productivity of 4-5 g/l/h and a high average productivity of 3 g/l/h. The work has also improved the final glycerol concentration in the fermented broth to over 330 g/l, reducing reactor volume and evaporation costs. The overall yield has reached a high value of 1g/2g of cornstarch. Another important character of the yeast is the fact that the cells are stable and active, leaving no residual glucose at the end of batch operations. This makes the downstream operation of vacuum distillation for purifying the final product easy to do, avoiding otherwise problems of charring of residual carbohydrates. These results have led to this proposed Phase II project which will evaluate various reactor systems, as well as high vacuum distillation for glycerol purification, employing industrial grade raw materials, over wide ranges of process variables and oxygen supply levels. This proposed Phase II study will obtain enough practical data to prepare for a future Phase III project.