Recombinant Yeast 2,3-Butanediol Production Pathway
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Solution Overview
Problem
Current microbial production of 2,3-butanediol is hindered by high production costs due to poor yield and the use of pathogenic bacteria, which poses safety concerns for large-scale fermentation, while GRAS microorganisms like Saccharomyces cerevisiae have inefficient conversion of pyruvate to 2,3-butanediol.
Innovation Solution
A recombinant yeast with reduced pyruvate decarboxylase activity is engineered by inserting nucleic acids encoding acetolactate synthase, acetolactate decarboxylase, butanediol dehydrogenase, and NADH oxidase to enhance the conversion of pyruvate to 2,3-butanediol, stabilizing the strain and increasing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If pathogenic bacteria (Klebsiella pneumonia, Enterobacter aerogenes) are used for 2,3-BDO production, then high yield and productivity are achieved, but safety concerns arise for large-scale fermentation
Solution Approach 1:
The patent replaces pathogenic bacteria with GRAS-certified yeast strains (Saccharomyces cerevisiae, Pichia pastoris) that are safe for industrial use. While bacterial systems offer higher theoretical productivity, the invention accepts a trade-off by using safe yeast hosts that can be disposed of after fermentation without safety concerns, enabling large-scale industrial production.
Solution Approach 2:
The patent introduces heterologous genes encoding 2,3-BDO biosynthetic enzymes (ilvA, ilvB, ilvC, ilvD from Bacillus subtilis or Paenibacillus polymyxa) into yeast hosts. These intermediary genetic elements enable the yeast to produce 2,3-BDO through a pathway not naturally present in the host, bridging the gap between safe host selection and desired product production.
2Object-affected harmful factors
If Saccharomyces cerevisiae is used for 2,3-BDO production, then safety is improved (GRAS status), but production yield deteriorates due to poor conversion of pyruvate to 2,3-BDO
Solution Approach 1:
The patent divides the 2,3-BDO biosynthetic pathway into discrete enzymatic steps and introduces separate genes for each enzyme (acetolactate synthase ilvA, acetolactate decarboxylase ilvB, 2,3-butaneediol dehydrogenase ilvC and ilvD). This segmentation allows each pathway step to be independently optimized and expressed in the yeast host, overcoming the natural inefficiency of pyruvate conversion.
Solution Approach 2:
The patent creates a composite genetic system by combining heterologous 2,3-BDO biosynthetic genes from Bacillus subtilis or Paenibacillus polymyxa with the Saccharomyces cerevisiae host genome. This composite approach integrates functional pathways from different organisms, enabling the yeast to acquire 2,3-BDO production capability while maintaining its safe GRAS status.
3Productivity
If Pdc-deficient mutant is used to minimize ethanol production, then 2,3-BDO production is improved, but industrial fermentation performance deteriorates
Solution Approach 1:
The patent applies local quality modification by specifically targeting and reducing pyruvate decarboxylase activity only in the context of ethanol production, while maintaining overall yeast viability and fermentation performance. The Pdc-deficient mutant strain (e.g., pdc1Δ pdc5Δ pdc6Δ) is used in combination with introduced 2,3-BDO pathway genes, allowing localized metabolic redirection without global strain deterioration.
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 yeast achieves a high yield of 2,3-butanediol close to the maximum theoretical yield, facilitating industrial production with improved strain stability and simplified purification.
Implementation Method 1
inserting nucleic acids encoding acetolactate synthase, acetolactate decarboxylase, butanediol dehydrogenase, and NADH oxidase to enhance the conversion of pyruvate to 2,3-butanediol
Implementation Method 2
microbial production of 2,3-BDO... Saccharomyces cerevisiae is an especially well suited platform for such bioprocesses
Implementation Method 3
increase the activity of a NADH-dependent enzyme and, possibly, the pool of NAD+
Data Source
AI summary
A recombinant yeast having a reduced pyruvate decarboxylase activity, in the génome of which has been inserted: —one or more nucleic acids encoding an acetolactate synthase or ALS, —one or more nucleic acids encoding an acetolactate decarboxylase or ALD, —one or more nucleic acids encoding a butancdiol dehydrogenase or BDH, and —one or more copies of a nucleic acids encoding a NADH oxidase or NOXE.