|Craig Jr, James|
Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/1997
Publication Date: N/A
Interpretive Summary: To improve the security of liquid fuel supplies, while creating jobs and businesses in rural areas, the government provides a tax incentive, promoting the use of ethanol in gasoline. Ethanol is produced from corn in fermentors, where yeast cells consume the glucose sugar that comes from the starch in the corn. However, ethanol produced this way is too expensive to compete directly with gasoline. A new process, continuous fermentation and stripping, was proposed to reduce the cost of producing ethanol. Stripping is a chemical engineering unit operation in which a volatile component of a liquid mixture is removed by contact with a gas. In this case, the product, ethanol, is continuously removed from the fermentor while it is produced, thereby greatly increasing the fermentation rate. This paper presents data from stable, long-term, continuous operation of this process in our pilot plant. The effects of ethanol concentration and temperature on the fermentation rate are revealed through analysis of the data. Application of this technology in the fuel ethanol industry could benefit not only ethanol producers, but corn farmers, transportation fuel consumers and taxpayers.
Technical Abstract: Operation of a pilot plant consisting of a 14-L fermentor, 4-in packed column and condenser for continuous fermentation and stripping of ethanol was stable for more than 100 days. The feed consisted of a non-sterile solution of 560 g/L glucose with 100 g/L corn steepwater. Fouling of the packing in the column with attached growth of yeast cells was controlled by in situ washing at intervals of 3 to 6 days. A computer simulation of the pilot plant was developed and used to analyze the data. Results are fit to linear models for the effects of ethanol concentration on specific growth rate and cell yield, and for the effect of stripping temperature on specific growth rate.