Ethanol fermentation in a three-phase tower fermentor using self-aggregating yeast
Abstract
A tower fermentor which utilizes self-aggregating yeast as a biocatalyst to convert sugars into ethanol was studied. Three phases (gas, liquid and solid) are involved in such a bioreactor. The self-aggregating yeast formed flocs in the bioreactor ranging in size from 2 to 3 mm in diameter. Due to the gravity effect, a packed bed region was formed in the lower portion of the tower fermentor. A mixed region (CSTR region) was formed on top of the packed bed region where yeast flocs were fluidized by carbon dioxide and liquid broth flowing upward. In the mixed region yeast flocs were in the range of 0.2-0.3 mm in diameter. Dilution rate, nutrient limitation, and hydrodynamic limitation are three major factors that significantly affect the height of the packed bed region. A mathematical model was developed to characterize the performance of this tower fermentor in the form of a serial connection of a packed bed and a CSTR bioreactor. This mathematical model can be used to predict the sugar and ethanol concentration profile within the tower fermentor, and the ethanol productivity. When sugarcane molasses is used as the carbon source, invertase can be recovered from the fermentation broth as a by-product of ethanol fermentation.
Degree
Ph.D.
Advisors
Chen, Purdue University.
Subject Area
Food science|Chemical engineering
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.