Fed-Batch Organic Acid Fermentation pH Control
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Solution Overview
Problem
Conventional fed-batch culture methods are unsuitable for organic acid production as they lead to continuous pH decrease, inhibiting microorganism growth and reducing fermentation efficiency, particularly in aerobic systems like E. coli, where pH-stat fed-batch cannot be applied due to sugar consumption-induced pH drops.
Innovation Solution
A method involving the fed-batch feeding of a carbon source substrate and a base, such as ammonium bicarbonate or alkali metal-containing weak bases, to maintain optimal pH and carbon source concentration during fermentation, allowing for continuous sugar feeding based on pH changes, thereby supporting anaerobic microorganism growth and maximizing organic acid production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high concentration of sugar is initially employed in batch culture to increase organic acid production, then the yield of organic acids increases, but the growth of microorganisms is inhibited and fermentation rate decreases
Solution Approach 1:
The patent divides the sugar feeding process into multiple stages: initial batch culture phase followed by fed-batch phase. This segmentation allows the system to benefit from both high initial sugar concentration and controlled subsequent feeding, resolving the contradiction between achieving high yield and maintaining high fermentation rate.
Solution Approach 2:
The patent implements dynamic sugar feeding control where the feeding rate is adjusted based on real-time monitoring of dissolved oxygen (DO) or pH parameters. This dynamic adjustment allows the system to adapt to changing microbial growth conditions, maintaining optimal fermentation rate while accumulating sufficient sugar for high organic acid yield.
2Ease of operation
If pH-stat fed-batch culture is used to control sugar feeding based on pH changes, then sugar concentration is maintained at minimal levels to support microorganism growth, but the method cannot be applied to organic acid production because the culture continuously decreases in pH
Solution Approach 1:
The patent inverts the conventional pH-stat logic by using pH decrease (caused by organic acid production) as the trigger for sugar feeding rather than pH increase. When pH drops below the set value during organic acid production, sugar is fed to stimulate further microbial growth and acid production, creating a feedback loop suitable for acid-producing organisms.
Solution Approach 2:
The patent changes the control parameter interpretation: instead of using pH as an indicator of sugar consumption (as in aerobic cultures), it uses pH as an indicator of organic acid accumulation. The feeding strategy is adjusted to compensate for the continuous pH decrease characteristic of anaerobic organic acid production, making the method adaptable to this specific fermentation type.
3Productivity
If manual sugar feeding at constant rate is used in fed-batch culture, then productivity and yield improve compared to batch culture, but the method is inefficient because sugar cannot be fed accurately with microorganism growth and sugar consumption
Solution Approach 1:
The patent implements automatic feedback control where dissolved oxygen (DO) or pH sensors continuously monitor microbial metabolic activity, and the sugar feeding rate is automatically adjusted in response to these signals. This feedback mechanism ensures sugar is fed at the precise rate matching microbial consumption, eliminating the inefficiencies of manual constant-rate feeding.
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 enhances productivity and yield by maintaining constant carbon source concentration, reducing by-product formation, and eliminating the need for expensive seed culture media, resulting in a more economical and efficient fermentation process.
Implementation Method 1
a base is fed in a fed-batch manner to maintain pH suitable for growth of microorganisms
Implementation Method 2
fermenting the carbon source substrate to produce an organic acid
Data Source
AI summary
The present invention provides a fed-batch culture method comprising a step of fed-batch-feeding a carbon source base and a base in such a manner that the pH level can be maintained at a level suitable for the growth of microorganisms for fermentation of a carbon source. The present invention also provides a method for preparing organic acids using the fed-batch culture method. The present invention fed-batch-feeds a neutralizing agent such as ammonium bicarbonate, ammonium carbonate or alkali metal-containing weak base, and a carbon source substrate in preparing organic acids by microorganism fermentation. Thus, a pH level suitable for the survival of microorganisms for carbon source fermentation can be maintained, and the speed of injecting the carbon source base which is the source material can be appropriately adjusted. The present invention may improve productivity, yield rate and concentration of organic acids and may automatically inject a base and a carbon source substrate according to a variation in the pH level, thus improving reliability and convenience of a fermentation process operation.