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Engineering Escherichia coli for the efficient conversion of glycerol to ethanol and co-products

Paper ID Volume ID Publish Year Pages File Format Full-Text
31889 44849 2008 12 PDF Available
Title
Engineering Escherichia coli for the efficient conversion of glycerol to ethanol and co-products
Abstract

Given its availability, low prices, and high degree of reduction, glycerol has become an ideal feedstock for producing reduced compounds via anaerobic fermentation. We recently identified environmental conditions enabling the fermentative metabolism of glycerol in E. coli, along with the pathways and mechanisms mediating this metabolic process. In this work, we used the knowledge base created in previous studies to engineer E. coli for the efficient conversion of crude glycerol to ethanol. Our strategy capitalized on the high degree of reduction of carbon in glycerol, thus enabling the production of not only ethanol but also co-products hydrogen and formate. Two strains were created for the co-production of ethanol–hydrogen and ethanol–formate: SY03 and SY04, respectively. High ethanol yields were achieved in both strains by minimizing the synthesis of by-products succinate and acetate through mutations that inactivated fumarate reductase (ΔfrdA) and phosphate acetyltransferase (Δpta), respectively. Strain SY04, which produced ethanol–formate, also contained a mutation that inactivated formate–hydrogen lyase (ΔfdhF), thus preventing the conversion of formate to CO2 and H2. High rates of glycerol utilization and product synthesis were achieved by simultaneous overexpression of glycerol dehydrogenase (gldA) and dihydroxyacetone kinase (dhaKLM), which are the enzymes responsible for the conversion of glycerol to glycolytic intermediate dihydroxyacetone phosphate. The resulting strains, SY03 (pZSKLMgldA) and SY04 (pZSKLMgldA), produced ethanol–hydrogen and ethanol–formate from unrefined glycerol at yields exceeding 95% of the theoretical maximum and specific rates in the order of 15–30 mmol/gcell/h. These yields and productivities are superior to those reported for the conversion of glycerol to ethanol–H2 or ethanol–formate by other organisms and equivalent to those achieved in the production of ethanol from sugars using E. coli.

Keywords
Metabolic engineering; Glycerol fermentation; Biofuels and biochemicals; Escherichia coli; Ethanol; Hydrogen; Formic acid
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Engineering Escherichia coli for the efficient conversion of glycerol to ethanol and co-products
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Publisher
Database: Elsevier - ScienceDirect
Journal: Metabolic Engineering - Volume 10, Issue 6, November 2008, Pages 340–351
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us