Lactic Acid Strain Engineering for High-Purity Isomer Production
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Solution Overview
Problem
Existing methods for producing lactic acid are inefficient and do not effectively produce optically pure L-lactic acid and D-lactic acid, which are crucial for improving the properties of biodegradable plastics like polylactic acid.
Innovation Solution
A method for constructing lactic acid-producing strains by genetically engineering a starting strain to introduce a lactic acid synthesis pathway, optimize it, and inhibit by-product synthesis pathways, using microorganisms like Bacillus and Geobacillus, and introducing L- or D-lactate dehydrogenase genes, while knocking out competing pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lactic acid production methods are used, then the process is simple, but the yield and purity of optically pure L-lactic acid and D-lactic acid are insufficient
Solution Approach 1:
The genetic engineering process is divided into three distinct stages: (1) introducing the lactic acid synthesis pathway by transforming host cells with plasmids containing ldh, pfk, and pyk genes; (2) optimizing the pathway through gene overexpression and metabolic flux adjustment; and (3) inhibiting by-product synthesis pathways through knockout mutations. This segmentation allows systematic improvement of chiral purity while managing complexity through modular approaches.
Solution Approach 2:
The patent extracts and eliminates competing metabolic pathways that produce by-products. Specifically, genes responsible for alternative metabolic routes are knocked out or suppressed, removing these harmful pathways from the cellular metabolism. This extraction approach directly improves chiral purity by preventing formation of unwanted stereoisomers and by-products.
2Loss of energy
If high-temperature fermentation is used, then cooling cost is reduced and contamination risk decreases, but the complexity of strain construction increases
Solution Approach 1:
The patent changes the operational temperature parameter from conventional mesophilic conditions to high-temperature fermentation (typically 40-70°C). This parameter change simultaneously achieves multiple benefits: reduced cooling energy consumption, decreased contamination risk from mesophilic organisms, and improved thermodynamic feasibility of certain reactions. The strain construction complexity is managed by selecting thermophilic host organisms and using temperature-stable genetic engineering tools.
3Productivity
If existing lactic acid-producing strains are used, then the strain construction is simple, but the production efficiency and yield are insufficient
Solution Approach 1:
The patent performs preliminary genetic modifications before actual lactic acid production. The host strain is pre-engineered with optimized lactic acid synthesis pathways, overexpressed enzymes, and inhibited by-product pathways. This preliminary action ensures that when production begins, the strain is already configured for high efficiency and high yield, avoiding the need for complex in-process modifications.
Solution Approach 2:
The patent creates composite genetic architectures by combining multiple gene components (ldh, pfk, pyk) into integrated expression systems. These composite genetic constructs work synergistically to maximize lactic acid production efficiency. The composite approach allows precise control over metabolic flux and product distribution, achieving high productivity that cannot be obtained through single-gene modifications.
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 method achieves high yields and purities of L-lactic acid and D-lactic acid, suitable for industrial applications, with titers up to 153.07 g L−1 and 151.12 g L−1, and chiral purities up to 99.63% and 99.04%, respectively, under high-temperature fermentation conditions.
Implementation Method 1
L-lactic acid and D-lactic acid can be widely used in food, medicine, cosmetics, and petrochemical industries. Most importantly, they can be used as precursors for use in the production of biodegradable plastic polylactic acid.
Implementation Method 2
L-lactic acid and D-lactic acid can be produced from catalysis of pyruvic acid by L-lactate dehydrogenase and D-lactate dehydrogenase, respectively, in the presence of cofactors.
Implementation Method 3
The efficient lactic acid-producing strains obtained using this strategy can be used to produce lactic acid by high-temperature fermentation.
Data Source
AI summary
Provided are a method for constructing a lactic acid-producing strain, a lactic acid-producing strain and use thereof. The method for constructing lactic acid-producing strains is characterized by genetically engineering a starting strain to increase lactic acid production, wherein the engineering includes: 1) introducing a lactic acid synthesis pathway; 2) optimizing the lactic acid synthesis pathway; and 3) inhibiting by-product synthesis pathways.