Recombinant Yeast NADPH Modulation for Ethanol Yield
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Solution Overview
Problem
Current recombinant yeast strains used for ethanol production from corn mash face limitations in maximizing ethanol yield and minimizing glycerol production, with existing strategies not fully realizing their potential due to insufficient NADP+ and NAD cofactor availability.
Innovation Solution
The development of recombinant yeast host cells with genetic modifications that downregulate the pentose phosphate pathway to reduce NADPH production and upregulate a second metabolic pathway using glyceraldehyde-3-phosphate dehydrogenase, allowing for increased glycolytic flux and reduced glycerol formation, thereby enhancing ethanol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pentose phosphate pathway is downregulated to reduce NADPH production, then ethanol yield is improved, but glycerol production decreases
Solution Approach 1:
The patent applies parameter changes by modifying the metabolic pathway parameters through genetic engineering. Specifically, it downregulates the pentose phosphate pathway (a first NADPH-generating pathway) and upregulates an alternative pathway involving glyceraldehyde-3-phosphate dehydrogenase (a second NADPH-generating pathway), thereby changing the NADPH generation parameters to favor ethanol production while reducing glycerol formation
Solution Approach 2:
The patent segments the NADPH generation process into two distinct metabolic pathways: the pentose phosphate pathway (downregulated) and the glyceraldehyde-3-phosphate dehydrogenase pathway (upregulated). This segmentation allows independent control of each pathway's contribution to NADPH production, enabling optimization of ethanol yield while minimizing glycerol byproduct formation
2Productivity
If NADPH production is reduced through pathway downregulation, then carbon flux to ethanol is improved, but cofactor availability becomes limiting
Solution Approach 1:
The patent introduces glyceraldehyde-3-phosphate dehydrogenase as an intermediary enzyme that mediates NADPH generation through an alternative pathway. This intermediary pathway bypasses the limitations of the downregulated pentose phosphate pathway, ensuring sufficient NADPH and NAD cofactor availability while maintaining enhanced carbon flux to ethanol production
Solution Approach 2:
The patent changes the metabolic parameters by introducing and upregulating the glyceraldehyde-3-phosphate dehydrogenase pathway, which has different cofactor requirements and kinetic properties compared to the pentose phosphate pathway. This parameter change ensures reliable cofactor availability while optimizing carbon flux distribution
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
This approach significantly increases ethanol yield while decreasing glycerol production, improving the efficiency of ethanol production from corn mash by optimizing carbon flux and cofactor utilization.
Implementation Method 1
The second genetic modification allows the expression of a glyceraldehyde-3-phosphate dehydrogenase lacking phosphorylating activity
Implementation Method 2
The first metabolic pathway and the second metabolic pathway allow the conversion of NADP+ to NADPH
Implementation Method 3
Saccharomyces cerevisiae is the primary biocatalyst used in the commercial production of fuel ethanol. This organism is proficient in fermenting glucose to ethanol
Data Source
AI summary
The present disclosure concerns recombinant yeast host cells having a first genetic modification for downregulating a first metabolic pathway that converts NADP+ to NADPH, as well as a second genetic modification for upregulating a second metabolic pathway that converts NADP+ to NADPH. The second genetic modification allows the expression of a glyceraldehyde-3-phosphate dehydrogenase lacking phosphorylating activity, which can, in some embodiments, be from enzyme commission 1.2.1.9 or 1.2.1.90. The second pathway is distinct from the first metabolic pathway. The present disclosure also concerns a process for making and improving the yield of a fermented product, such as ethanol, using the recombinant yeast host cell.