Microbial Strain Adaptation for Organic Acid End-Product Inhibition
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Solution Overview
Problem
Existing methods for commercial-scale microbial production of organic acids face challenges such as end-product inhibition and low yield due to the inhibitory effect of organic acids on microbial growth, which are not effectively addressed by current genetic manipulations or pH-controlled fermentation processes.
Innovation Solution
A method involving serial passage of microbial cell lines in pH-controlled culture media supplemented with organic acids at a pH above the pKa value of the acid, primarily targeting mutations in the cellular envelope functions to enhance organic acid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional genetic manipulations or pH-controlled fermentation processes are used, then microbial growth is maintained, but organic acid production is inhibited due to end-product inhibition
Solution Approach 1:
The patent applies parameter changes by controlling pH above the pKa value of the organic acid (e.g., pH 6.5-7.5 for propionic acid with pKa 4.87). This parameter change shifts the equilibrium between undissociated and dissociated forms of the organic acid, reducing the concentration of the inhibitory undissociated form and thereby alleviating end-product inhibition while maintaining high productivity
Solution Approach 2:
The patent converts the harmful effect of organic acid accumulation into a beneficial selection pressure. By supplementing culture media with organic acid during serial passage, the method selects for mutant strains with enhanced tolerance and production capabilities, turning the inhibitory substance into a tool for strain improvement
2Productivity
If organic acid concentration in culture media is increased to inhibit microbial growth, then selection for overproducing strains is achieved, but growth rate and doubling time are reduced
Solution Approach 1:
The patent applies preliminary action by pre-adapting strains through serial passage in organic acid-supplemented media before production fermentation. This preliminary exposure selects for mutants with improved acid tolerance, ensuring that the production strain can withstand high organic acid concentrations during scale-up while maintaining acceptable growth rates
Solution Approach 2:
The patent uses periodic serial passage through multiple generations in progressively more acidic conditions. This periodic selection process gradually enriches the population for acid-tolerant mutants, allowing the strain to adapt to high organic acid concentrations over time while maintaining growth capability
3Ease of manufacture
If serial passage is performed in non-immobilized culture, then process simplicity is maintained, but control over cell growth and acid production is reduced
Solution Approach 1:
The patent implements feedback control by monitoring pH and organic acid concentration during serial passage and adjusting supplementation levels accordingly. This feedback mechanism allows optimization of the balance between selection pressure and cell viability, maintaining process simplicity while achieving effective strain improvement
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 results in microbial strains with increased organic acid production, overcoming end-product inhibition and achieving higher yields in a shorter timeframe compared to conventional methods, with the produced acids being suitable for labeling as 'organic' or 'natural preservatives'.
Implementation Method 1
The method uses serial passage of a parental strain in pH-controlled culture media supplemented with the organic acid
Data Source
AI summary
Microbial cell lines suitable for industrial-scale production of organic acids and methods of making and isolating such cell lines, and using the cell lines for production of organic acids.