Reducing Acetic Acid in Corynebacterium via Ach Gene Disruption
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Solution Overview
Problem
Coryneform bacteria used in fermentation for producing L-amino acids, such as L-glutamic acid, under oxygen-limited conditions accumulate excess organic acids like acetic acid, reducing productivity and increasing production costs, as existing methods fail to effectively decrease acetic acid production.
Innovation Solution
Decreasing acetyl-CoA hydrolase activity in coryneform bacteria by introducing mutations or disrupting the acetyl-CoA hydrolase gene, thereby reducing acetic acid production and enhancing the bacteria's ability to produce L-amino acids like L-glutamic acid, L-valine, and L-alanine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If coryneform bacteria are cultured under oxygen-limited conditions to produce L-amino acids, then L-amino acid production occurs, but organic acids (acetic acid, lactic acid) accumulate in excess amounts as byproducts
Solution Approach 1:
The invention extracts and eliminates the harmful byproduct formation pathway by disrupting the acetyl-CoA hydrolase gene (ach gene), which is responsible for acetic acid production. This selective removal of the harmful metabolic route allows the bacteria to channel more carbon flux toward L-amino acid production while minimizing organic acid accumulation.
Solution Approach 2:
The invention changes the metabolic parameters of the bacteria by modifying gene expression levels. Specifically, it disrupts the ach gene to reduce acetyl-CoA hydrolase activity, thereby altering the metabolic flux distribution. This parameter change redirects carbon flow away from acetic acid production and toward L-amino acid biosynthesis, resolving the contradiction between productivity and byproduct formation.
2Object-generated harmful factors
If acetyl-CoA hydrolase activity is decreased to reduce acetic acid production, then by-product formation decreases, but the mechanism for achieving this decrease needs to be established
Solution Approach 1:
The invention converts the harmful effect of acetyl-CoA metabolism into a beneficial outcome. By disrupting the ach gene that causes acetic acid production, the bacteria are forced to utilize alternative metabolic pathways that favor L-amino acid synthesis. The harmful acetyl-CoA hydrolase pathway is transformed into a beneficial redirection of metabolic flux toward the desired product.
Solution Approach 2:
The invention takes out the problematic acetyl-CoA hydrolase enzyme system from the bacterial metabolism by gene disruption. This extraction eliminates the source of acetic acid production while preserving the essential acetyl-CoA pool for other biosynthetic pathways, including L-amino acid production.
3Stability of the object's composition
If excess counter ions are added to neutralize organic acids, then pH control is maintained, but production cost increases
Solution Approach 1:
The invention performs preliminary action by genetically modifying the bacteria before fermentation to prevent organic acid accumulation in the first place. By disrupting the ach gene, the system proactively eliminates the source of pH instability, thereby avoiding the need for subsequent corrective actions involving counter ion addition and associated costs.
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 modified bacteria exhibit improved productivity and reduced by-product formation, leading to increased yields of L-amino acids with decreased acetic acid production, thus optimizing fermentation processes.
Implementation Method 1
Acetyl-CoA hydrolase (3.1.2.1) produces acetic acid from acetyl-CoA and H2O
Implementation Method 2
The present invention relates to a method for producing L-amino acids generated via a biosynthetic pathway in which pyruvic acid is an intermediate during fermentation of coryneform bacteria
Data Source
AI summary
Coryneform bacteria are described that have an ability to produce L-amino acids and are modified so that acetyl-CoA hydrolase activity is decreased. The bacteria are used to produce L-amino acids generated by a biosynthetic pathway in which pyruvic acid is an intermediate, such as L-glutamic acid, L-arginine, L-glutamine, L-proline, L-alanine, L-valine, and L-lysine.