L-Cystine Fermentation Oxygen Saturation Control
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Solution Overview
Problem
Existing methods for producing L-cystine by fermentation result in product heterogeneity, with L-cystine, L-cysteine, and thiazolidine present in the culture broth, making purification challenging due to the varying forms of the amino acid and its derivatives.
Innovation Solution
Maintaining oxygen saturation of the fermentation medium between 1% and 40% to promote the precipitation of L-cystine to at least 70% of the total cysteine formed, utilizing modified microorganisms with reduced feedback inhibition and enhanced efflux genes for increased production and export of L-cysteine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional fermentation methods are used for L-cystine production, then L-cysteine is produced in the culture broth, but product heterogeneity occurs with L-cystine, L-cysteine, and thiazolidine present, making purification challenging
Solution Approach 1:
The patent applies parameter changes by controlling oxygen saturation at 40±3% and pH at 6.5-7.5 during fermentation to shift the oxidation equilibrium, maximizing L-cystine formation while minimizing L-cysteine and thiazolidine accumulation, thereby achieving both high production and product homogeneity
Solution Approach 2:
The patent employs feedback control by continuously monitoring oxygen saturation and pH levels, and adjusting aeration and base addition rates accordingly to maintain optimal conditions for L-cystine precipitation and prevent formation of other cysteine derivatives
2Productivity
If oxygen saturation is increased to promote L-cystine formation, then oxidation reaction is enhanced, but solubility of L-cystine increases, reducing precipitation efficiency
Solution Approach 1:
The patent identifies an optimal oxygen saturation range (40±3%) that balances oxidation rate and solubility effects, maintaining conditions that favor both L-cystine formation and precipitation, while controlling pH to enhance precipitation efficiency
3Ease of manufacture
If fermentation conditions are optimized for L-cystine precipitation, then purification is simplified, but control complexity increases due to oxygen saturation and pH monitoring requirements
Solution Approach 1:
The patent implements automated feedback control systems with oxygen sensors and pH meters that continuously monitor fermentation parameters and automatically adjust aeration and base addition, simplifying operation while maintaining precise control over L-cystine precipitation conditions
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 ensures that L-cystine precipitates in high amounts, simplifying purification and increasing product yield by shifting the reaction equilibrium, allowing for efficient separation and recovery of L-cystine from the fermentation broth.
Implementation Method 1
L-cysteine plays a key role in sulfur metabolism in all organisms and is used in the synthesis of proteins, glutathione, biotin, lipoic acid, methionine and other sulfur-containing metabolites. In addition, L-cysteine serves as precursor for the biosynthesis of coenzyme A.
Implementation Method 2
a method for producing L-cysteine by fermentation was also developed some years ago. The prior art with respect to the production of L-cysteine by fermentation using microorganisms has been described in detail e.g. in U.S. Pat. Nos. 6,218,168B1, 5,972,663A, U.S.2004/0038352A1, CA2386539A1, U.S.2009/0053778A1 and U.S.2009/0226984A1.
Implementation Method 3
The increase of the transport of L-cysteine out of the cell is a further possibility to increase the product yield in the medium. This may be achieved by overexpression of so-called efflux genes. These genes code for membrane-bound proteins which mediate the export of L-cysteine from the cell.
Data Source
AI summary
The invention relates to a method for producing L-cystine by fermenting a microorganism strain in a fermentation medium, in which method L-cystine is precipitated in an amount of at least 70% relative to the total cysteine, characterized in that the O2 saturation of the fermentation medium is kept at least at 1% and at most at 40±3% during the formation of L-cystine.