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Ethanol from Whey: Continuous Fermentation with a Catabolite Repression-Resistant Saccharomyces cerevisiae Mutant
S L Terrell1, A Bernard, R B Bailey
1Biotechnology Branch, Solar Energy Research Institute, Golden, Colorado 80401.
Applied and Environmental Microbiology
|September 1, 1984
Summary
This study demonstrates an efficient method for converting cheese whey lactose into ethanol using Saccharomyces cerevisiae. Continuous-culture technology and cell-recycle systems optimize ethanol production, achieving high yields.
Area of Science:
- Biotechnology
- Industrial Microbiology
- Fermentation Technology
Background:
- Cheese whey, a byproduct of the dairy industry, contains lactose that can be converted into valuable products.
- Traditional methods for lactose fermentation face challenges like catabolite repression and low yields.
- Development of efficient bioconversion processes is crucial for sustainable industrial practices.
Purpose of the Study:
- To demonstrate an alternative method for converting cheese whey lactose into ethanol.
- To optimize ethanol production using continuous-culture technology and a catabolite repression-resistant Saccharomyces cerevisiae mutant.
- To enhance fermentor productivity through cell-recycle systems and controlled fed-batch operations.
Main Methods:
- Utilized a catabolite repression-resistant mutant of Saccharomyces cerevisiae.
- Employed computer-controlled fed-batch fermentation based on carbon dioxide evolution rate.
- Implemented a continuous anaerobic fermentation process with a cell-recycle system.
- Investigated fermentation of equimolar glucose and galactose mixtures derived from lactose.
Main Results:
- Achieved complete fermentation of glucose and galactose mixtures into ethanol.
- Obtained high biomass concentrations prior to continuous fermentation using fed-batch operation.
- Maximized fermentor productivity at 13.6 g/L/h with 15% substrate and a dilution rate of 0.2 h⁻¹, maintaining low residual sugar (<1%).
- Demonstrated complete fermentation of 20% concentrated feed solutions, albeit with reduced productivity (5.5 g/L/h).
Conclusions:
- Continuous-culture technology with cell-recycle systems offers an efficient route for ethanol production from cheese whey lactose.
- Optimized fermentation parameters, including substrate concentration and dilution rate, are key to maximizing productivity.
- The developed method provides a sustainable approach for valorizing dairy industry byproducts.