Recombinant Microorganism Electron Pathway for Ethanol Yield
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Solution Overview
Problem
Current strategies for reducing glycerol production in ethanol fermentation, such as engineering ammonia fixation or expressing NADPH-linked glyceraldehyde-3-phosphate dehydrogenase, either partially reduce glycerol formation or create by-products, leading to significant ethanol yield loss in industrial corn ethanol fermentations.
Innovation Solution
A recombinant microorganism is developed with genetic modifications that include encoding phosphoketolase, bifunctional acetaldehyde-alcohol dehydrogenase, and down-regulating enzymes in the glycerol-production pathway, such as glycerol-3-phosphate dehydrogenase, to redirect electrons towards ethanol formation, thereby reducing glycerol production and increasing ethanol yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If glycerol production is reduced by engineering ammonia fixation or expressing NADPH-linked glyceraldehyde-3-phosphate dehydrogenase, then glycerol formation is partially reduced, but ethanol yield loss increases significantly
Solution Approach 1:
The invention changes the redox balance parameters by introducing NADPH-dependent enzymes (glyceraldehyde-3-phosphate dehydrogenase and glycerol dehydrogenase) to alter the electron carrier system from NADH to NADPH, thereby enabling glycerol reduction without compromising ethanol yield
Solution Approach 2:
The invention uses NADPH as an intermediary electron carrier to mediate between carbon metabolism and glycerol production, allowing electrons to be diverted to glycerol synthesis without affecting the NADH-dependent ethanol fermentation pathway
2Quantity of substance
If glycerol production is reduced by current strategies, then glycerol formation decreases, but by-products are created
Solution Approach 1:
The invention converts the harmful by-product formation into beneficial ethanol production by engineering the microorganism to produce ethanol from the intermediates that would otherwise form by-products, while simultaneously reducing glycerol formation through NADPH-dependent pathways
3Productivity
If electrons are redirected towards ethanol formation, then ethanol yield increases, but glycerol production decreases
Solution Approach 1:
The invention segments the electron flow into two independent pathways: NADH-dependent ethanol fermentation and NADPH-dependent glycerol production, allowing simultaneous optimization of both ethanol yield and glycerol reduction without mutual interference
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The recombinant microorganism achieves a higher ethanol yield, with an increase of 1%-10% and a corresponding reduction of 10-100% in glycerol production compared to unmodified microorganisms, when cultured with carbon-containing feedstocks like woody biomass or agricultural wastes.
Implementation Method 1
the fermentation of hexose sugars (e.g., glucose, mannose, and galactose); and (4) the fermentation of pentose sugars (e.g., xylose and arabinose)
Implementation Method 2
A recombinant microorganism is developed with genetic modifications that include encoding phosphoketolase, bifunctional acetaldehyde-alcohol dehydrogenase
Data Source
AI summary
The present invention provides for a mechanism to completely replace the electron accepting function of glycerol formation with an alternative pathway to ethanol formation, thereby reducing glycerol production and increasing ethanol production. In some embodiments, the invention provides for a recombinant microorganism comprising a down-regulation in one or more native enzymes in the glycerol-production pathway. In some embodiments, the invention provides for a recombinant microorganism comprising an up-regulation in one or more enzymes in the ethanol-production pathway.