Recombinant Zymomonas Mobilis Fermentation for High-Purity D-Lactic Acid
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Solution Overview
Problem
Existing microbial fermentation processes for producing D-lactic acid are limited by low yield and high ethanol production, which complicates downstream processing and reduces the efficiency of lactic acid production.
Innovation Solution
Genetic engineering of Zymomonas mobilis by knocking out specific loci and introducing the LmldhA gene and a 2,3-BDO operon to redirect metabolic pathways towards D-lactic acid production, utilizing the CRISPR-Cas system for precise gene editing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional fermentation methods are used, then the process is simple to operate, but the yield of D-lactic acid is low and ethanol production is high
Solution Approach 1:
The patent extracts and removes the harmful ethanol production pathway by knocking out the pdc gene (pyruvate decarboxylase) which is responsible for ethanol synthesis. This eliminates the competing pathway that diverts carbon flux away from lactic acid production, thereby increasing D-lactic acid yield while removing the harmful byproduct
Solution Approach 2:
The patent changes the metabolic parameters by introducing the LmldhA gene encoding D-lactate dehydrogenase from Lactococcus lactis, which alters the enzyme kinetics and metabolic flux to favor D-lactic acid production. This genetic modification changes the biochemical parameters of the fermentation process to achieve high yield and high optical purity
2Productivity
If traditional fermentation methods are used, then the process is simple, but the efficiency of lactic acid production is reduced due to complex downstream processing
Solution Approach 1:
By achieving >99% optical purity through genetic engineering, the patent changes the product specification parameter to such an extent that complex separation and purification processes become unnecessary. The high optical purity is achieved in-situ through the LmldhA gene introduction, eliminating the need for complex downstream processing equipment and operations
3Productivity
If gene editing is performed to improve yield, then D-lactic acid production efficiency increases, but the genetic modification process becomes more complex
Solution Approach 1:
The patent uses the CRISPR-Cas9 system as an intermediary tool to achieve precise gene editing. This molecular machinery serves as a mediator that guides the editing process through the guide RNA-cas9 complex, enabling specific gene knockouts and insertions with high precision while maintaining relative simplicity in the overall 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
The engineered Zymomonas mobilis strain achieves high yield and high production efficiency of D-lactic acid, with glucose conversion rates exceeding 99% and optical purity of 99.1%, overcoming the limitations of traditional fermentation methods.
Implementation Method 1
utilizing the CRISPR-Cas system for precise gene editing
Implementation Method 2
fermenting the recombinant Zymomonas mobilis in a medium containing glucose
Data Source
AI summary
Recombinant Zymomonas mobilis and method are provided. The recombinant Zymomonas mobilis carries a recombinant genome by genetic engineering means from the wild genome of ZM4 strain, and produces D-lactic acid.