Recombinant Yeast Lactic Acid Production via pH Shift
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Solution Overview
Problem
Current methods for producing lactic acid using lactic acid bacteria face challenges such as high production costs due to expensive purification processes, limited viability at low pH, and the need for organic nitrogen sources, which complicates the production of high-purity, optically pure isomers.
Innovation Solution
A two-step fermentation process using recombinant yeast strains engineered with lactate dehydrogenase (LDH) activity and decreased or knocked-out pyruvate decarboxylase (PDC) activity, where the yeast is cultivated at a pH of 5 to 7 for biomass production and then at a low pH for lactic acid production, allowing for efficient lactic acid yield and reduced fermentation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lactic acid bacteria are used for lactic acid production, then the acid can be produced naturally, but the purification process becomes expensive and complex
Solution Approach 1:
The patent changes the pH parameter throughout the fermentation process. By maintaining high pH (7.0-9.0) during fermentation, lactic acid is produced in its ionized form which remains soluble and does not require acidification for purification. This parameter change eliminates the need for expensive acidification and salt removal steps required by conventional low-pH processes.
2Productivity
If lactic acid bacteria are used for lactic acid production, then production can proceed, but organic nitrogen sources are required which complicates the process
Solution Approach 1:
The patent changes the pH parameter to alkaline conditions (7.0-9.0), which enables the use of inorganic nitrogen sources instead of organic nitrogen sources. This parameter change simplifies the medium composition and reduces process complexity while maintaining high lactic acid production efficiency.
3Quantity of substance
If conventional fermentation processes are used, then lactic acid can be produced, but acidification and salt removal are required for purification
Solution Approach 1:
The patent maintains alkaline pH (7.0-9.0) throughout the entire fermentation process, which keeps lactic acid in its ionized, soluble form. This eliminates the need for acidification and salt removal steps that are required in conventional low-pH processes, significantly simplifying the purification process while maintaining high lactic acid yield.
4Productivity
If fermentation time is extended to increase lactic acid yield, then productivity improves, but exposure to stress conditions increases
Solution Approach 1:
The patent changes the pH parameter to alkaline conditions (7.0-9.0), which creates a less stressful environment for the microorganisms during fermentation. This allows for extended fermentation times to maximize lactic acid yield without subjecting the cells to prolonged acid stress, thereby maintaining cell viability and metabolic activity throughout the process.
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 significantly reduces production costs, enhances productivity, and simplifies purification by avoiding the need for acidification and salt removal, resulting in high-purity lactic acid with reduced exposure to stress conditions.
Implementation Method 1
a yeast strain that is engineered to have lactate dehydrogenase (LDH) activity
Implementation Method 2
a two-step fermentation process using recombinant yeast strains
Data Source
AI summary
The present invention provides a method for producing lactic acid in a recombinant yeast cell culture using glucose as carbon source comprising a first, seed fermentation stage to produce biomass wherein the yeast is cultivated in a culture medium at a pH of 5 to 7, followed by a second, a production fermentation stage with biomass from the seed fermentation to produce lactic acid, wherein the yeast is cultivated in a culture medium at low p H using a yeast strain that is engineered to have lactate dehydrogenase (LDH) activity and optionally has decreased or knocked-out pyruvate decarboxylase (PDC) activity.