Cofactor Purge Valve Pathway for Balanced Microbial Chemical Yield
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Solution Overview
Problem
Existing metabolic engineering methods face challenges in achieving high yields of low-value/high-volume commodity chemicals due to competing biochemical pathways and imbalances in co-factor utilization, particularly in microbial systems.
Innovation Solution
A recombinant metabolic pathway with a purge valve system that recycles co-factors, such as NAD+/NADH and NADP+/NADPH, using enzymes like NADH dehydrogenase and NADPH dehydrogenase, to maintain co-factor balance and optimize production of chemicals like PHB and isoprene.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional metabolic engineering methods are used to produce commodity chemicals in microbes, then cell viability is maintained through competing biochemical pathways, but high yields required for economic viability cannot be achieved
Solution Approach 1:
The metabolic pathway is segmented into multiple independent enzymatic steps, each catalyzed by a specific enzyme. This allows independent optimization and control of each step to maximize overall pathway efficiency and chemical yield while maintaining cell viability through balanced cofactor management at each segment.
Solution Approach 2:
The system dynamically adjusts cofactor balance by introducing a purge valve pathway that converts excess NADPH to NADH when NADPH levels become unbalanced. This parameter change in cofactor ratios enables high productivity by preventing cofactor bottlenecks while maintaining cell viability through balanced redox state.
2Productivity
If competing biochemical pathways are present for cell viability, then metabolic flexibility is maintained, but high yields of desired chemicals cannot be achieved
Solution Approach 1:
The purge valve pathway extracts and removes excess cofactors (NADPH) that would otherwise accumulate and cause metabolic imbalance. By taking out the excess cofactor through a dedicated recycling pathway, the system achieves high chemical yields without compromising the metabolic flexibility needed for cell viability.
Solution Approach 2:
The purge valve pathway implements feedback control by sensing cofactor imbalance and activating the NADPH-to-NADH conversion pathway only when needed. This feedback mechanism maintains optimal cofactor ratios for high productivity while preserving metabolic flexibility for cell survival under varying conditions.
3Productivity
If cofactor utilization is unbalanced in the pathway, then metabolic simplicity is maintained, but production efficiency decreases
Solution Approach 1:
The purge valve pathway acts as an intermediary system that mediates between the main production pathway and the cofactor pool. By introducing this intermediate pathway that converts NADPH to NADH, the system achieves balanced cofactor utilization and high production efficiency without requiring complete redesign of the entire metabolic network.
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 system achieves nearly 100% yield of desired products by regulating co-factor utilization, maintaining co-factor balance, and is robust to variations in co-factor levels, overcoming the limitations of traditional methods.
Implementation Method 1
a recombinant metabolic pathway comprising a plurality of enzymatic steps that converts a substrate to a product
Implementation Method 2
an enzyme that uses the co-factor to convert a metabolite in one or more of the plurality of enzymatic steps
Data Source
AI summary
The disclosure provides a metabolic pathway for producing a metabolite, the metabolic pathway having a co-factor purge valve system for recycling a cofactor used in the metabolic pathway.