Modifying Yeast Gpd1 and Gpd2 to Increase Ethanol Yield
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Solution Overview
Problem
Current methods for reducing glycerol production in yeast during ethanol fermentation are ineffective as they either impair cell growth or are not industrially relevant, as glycerol biosynthesis serves essential functions for stress tolerance and redox balance.
Innovation Solution
Modifying yeast cells by reducing the activity of Gpd1 and/or Gpd2 proteins through methods such as using weak promoters, antisense molecules, ribozymes, or inhibitors to minimize glycerol production without affecting cell growth, allowing for increased ethanol yield and reduced waste volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If glycerol formation is completely abolished by deleting GPD1 and GPD2, then ethanol yield is increased by 12%, but cell growth is severely affected
Solution Approach 1:
Instead of completely abolishing glycerol formation by deleting both GPD1 and GPD2 genes, the patent applies partial action by deleting only GPD2 and partially downregulating GPD1 (reducing its expression by 50-90%). This partial approach maintains sufficient glycerol production for cell growth and stress tolerance while still redirecting enough carbon flux to ethanol to achieve improved productivity, thus resolving the contradiction between ethanol yield and cell growth.
Solution Approach 2:
The patent applies local quality by differentially treating the two GPD genes: GPD2 is completely deleted while GPD1 is partially downregulated. This asymmetric approach recognizes that the two genes have different functional roles, with GPD1 being more critical for maintaining cell fitness. By applying different levels of gene suppression to different parts of the glycerol biosynthetic pathway, the patent achieves both improved ethanol yield and maintained cell growth.
2Productivity
If glycerol formation is reduced to increase ethanol yield, then ethanol productivity is improved, but cell fitness and stress tolerance are negatively affected
Solution Approach 1:
The patent applies partial action by reducing rather than eliminating glycerol formation. By partially downregulating GPD1 expression and selectively deleting GPD2, the patent achieves a balance where glycerol production is reduced enough to improve ethanol productivity (by maintaining cell growth and stress tolerance capabilities), while still producing sufficient glycerol to support cell fitness and stress response mechanisms.
3Productivity
If GPD1 and GPD2 are deleted to eliminate glycerol production, then carbon flux towards ethanol is increased, but respiratory NADH reoxidation capacity is limited
Solution Approach 1:
The patent applies partial action by maintaining residual GPD1 activity rather than completely eliminating glycerol biosynthesis capacity. This partial retention of GPD1 function preserves sufficient NADH reoxidation capacity through the glycerol pathway while still redirecting adequate carbon flux to ethanol production, thus resolving the contradiction between carbon flux to ethanol and NADH reoxidation capacity.
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 increases ethanol yield and productivity while maintaining cell growth rates, reducing glycerol production and associated costs, and is applicable under various industrial conditions.
Implementation Method 1
Glycerol biosynthesis from the glycolytic intermediate dihydroxyacetone phosphate (DHAP) in S. cerevisiae is performed by two enzymatic steps catalyzed by the glycerol 3-phosphate dehydrogenase (GPDH)
Implementation Method 2
Glycerol biosynthesis from the glycolytic intermediate dihydroxyacetone phosphate (DHAP) in S. cerevisiae is performed by two enzymatic steps catalyzed by the glycerol 3-phosphate dehydrogenase (GPDH) and the glycerol 3-phosphatase (GPP)
Implementation Method 3
The yeast Saccharomyces (S.) cerevisiae has been traditionally used in this process... beside the main fermentation products: ethanol, carbon dioxide and biomass
Data Source
AI summary
The invention relates to a method of modifying a yeast cell for the production of ethanol. According to some embodiments of the invention, the activity of the Gpd1 protein and/or the Gpd2 protein is reduced.