Production of ethanol from thin stillage by metabolically engineered Escherichia coli
- Ramon GonzalezAffiliated withDepartment of Chemical and Biomolecular Engineering, Rice UniversityDepartment of Bioengineering, Rice University Email author
- , Paul CampbellAffiliated withGlycos Biotechnologies Inc.
- , Matthew WongAffiliated withGlycos Biotechnologies Inc.
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Thin stillage is a by-product generated in large amounts during the production of ethanol that is rich in carbon sources like glycerol, glucose and maltose. Unfortunately, the fermentation of thin stillage results in a mixture of organic acids and ethanol and minimum utilization of glycerol, the latter a compound that can represent up to 80% of the available substrates in this stream. We report here the efficient production of ethanol from thin stillage by a metabolically engineered strain of Escherichia coli. Simultaneous utilization of glycerol and sugars was achieved by overexpressing either the fermentative or the respiratory glycerol-utilization pathway. However, amplification of the fermentative pathway (encoded by gldA and dhaKLM) led to more efficient consumption of glycerol and promoted the synthesis of reduced products, including ethanol. A previously constructed strain, EH05, containing mutations that prevented the accumulation of competing by-products (i.e. lactate, acetate, and succinate) and overexpressing the fermentative pathway for glycerol utilization [i.e. strain EH05 (pZSKLMgldA)], efficiently converted thin stillage supplemented with only mineral salts to ethanol at yields close to 85% of the theoretical maximum. Ethanol accounted for about 90% (w/w) of the product mixture. These results, along with the comparable performance of strain EH05 (pZSKLMgldA) in 0.5 and 5 l fermenters, indicate a great potential for the adoption of this process by the biofuels industry.
KeywordsBiofuels Metabolic engineering Glycerol fermentation Escherichia coli Thin stillage Ethanol
- Production of ethanol from thin stillage by metabolically engineered Escherichia coli
Volume 32, Issue 3 , pp 405-411
- Cover Date
- Print ISSN
- Online ISSN
- Springer Netherlands
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- Metabolic engineering
- Glycerol fermentation
- Escherichia coli
- Thin stillage
- Industry Sectors
- Author Affiliations
- 1. Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, MS-362, Houston, TX, 77005, USA
- 2. Department of Bioengineering, Rice University, Houston, TX, USA
- 3. Glycos Biotechnologies Inc., Houston, TX, USA