Fermentation kinetics and process economics for the production of ethanol
The aim of this study was to develop and optimize fermentation technology for the production of ethanol. Using glucose as the fermentable substrate, optimal fermentation parameters of pH, temperature, oxygen tension, and sugar concentration were determined in both batch and continuous culture. The experimental results indicate that although ethanol fermentation is an anaerobic process, trace amounts of oxygen are required for maximal ethanol production. The ethanol productivity of the initial culture of Saccharomyces cerevisiae (ATCC No. 4126) was optimal at an oxygen tension of 0.7 mmHg and a temperature of 35/sup 0/C. However, when long term continuous culture was maintained the yeast ''adapted'' after 3 weeks of operation, requiring an oxygen tension of only 0.07 mmHg for optimal ethanol production, 43 percent higher than for unadapted yeast. A cell recycle system employing an external settler to increase the biomass concentration in continuous fermentations was examined. In addition, a novel vacuum fermentation scheme was developed whereby ethanol is boiled away from the fermentation broth as it is produced. By combining the vacuum fermentation with cell recycle, yeast cell densities of 124 g dry wt/1 were achieved resulting in a 14-fold increase in ethanol productivity over simple continuous operation. From the experimental results obtained industrial size ethanol fermentation plants were designed and an economic evaluation conducted. The process design studies indicated that over a 50 percent reduction in capital expenditure may be obtained by continuous rather than batch operation. Further reductions in processing costs were achieved by both cell recycle and vacuum operation. However, the cost of fermentable substrate, either molasses or enzymatic hydrolysate sugars, dominates the economics of ethanol production.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 7274757
- Report Number(s):
- LBL-4480
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ETHANOL
BIOSYNTHESIS
GLUCOSE
FERMENTATION
ANAEROBIC CONDITIONS
BIOCHEMICAL REACTION KINETICS
ECONOMICS
INDUSTRIAL PLANTS
OXYGEN
PH VALUE
TEMPERATURE DEPENDENCE
ALCOHOLS
ALDEHYDES
BIOCONVERSION
CARBOHYDRATES
CRYOGENIC FLUIDS
ELEMENTS
FLUIDS
HEXOSES
HYDROXY COMPOUNDS
KINETICS
MONOSACCHARIDES
NONMETALS
ORGANIC COMPOUNDS
REACTION KINETICS
SACCHARIDES
SYNTHESIS
090222* - Alcohol Fuels- Preparation from Wastes or Biomass- (1976-1989)