Genetically Engineered E. coli for High-Titer L-Theanine Fermentation
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Solution Overview
Problem
Current methods for producing L-theanine via microbial fermentation face challenges such as high production costs due to expensive raw materials, low yield, and complex fermentation broths with many by-products, as well as difficulties in achieving high-purity separation and extraction.
Innovation Solution
A genetically engineered bacterium, E. coli THEE, is developed by integrating specific genes like fructose 6-phosphate phosphoketolase, phosphoacetyl transferase, and citrate synthase, and using CRISPR/Cas 9-mediated gene editing to enhance metabolic pathways, combined with a controlled ethylamine feeding strategy and membrane separation techniques for efficient L-theanine production and purification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L-theanine is produced via enzymatic synthesis using microorganisms with glutamine, glutamate and ATP as substrates, then the synthesis can be achieved, but the production cost is very high
Solution Approach 1:
The patent replaces expensive substrates (glutamine, glutamate, ATP) with cheap glucose as the carbon source. The engineered bacterium converts glucose through metabolic pathways to produce L-theanine, eliminating the need for costly amino acid substrates and making large-scale production economically viable
Solution Approach 2:
The patent changes the substrate parameter from expensive amino acids (glutamine, glutamate) to inexpensive glucose. By modifying the metabolic pathway parameters through gene integration and knockout, the system achieves L-theanine production from a cheaper, more readily available carbon source
2Ease of manufacture
If L-theanine is produced via fermentation with glucose as raw material, then the production cost is reduced, but the titer is low and yield is reduced with more by-products
Solution Approach 1:
The patent segments the metabolic pathway into specific controlled steps by integrating key enzyme genes (phosphoketolase, phosphoacetyl transferase, citrate synthase) and knocking out competing pathways (acetokinase, malic enzyme). This segmentation directs metabolic flux toward L-theanine production, increasing yield and reducing by-products while maintaining low production cost
Solution Approach 2:
The patent optimizes fermentation parameters including pH control (6.8-7.2), temperature (30-37°C), dissolved oxygen (15-30%), and ethylamine feeding rate (0.5-2.0 g/L/h). These parameter changes maximize L-theanine titer and yield while minimizing by-product formation during glucose fermentation
3Reliability
If ethylamine is added to produce L-theanine, then the synthesis can proceed, but ethylamine has an inhibiting effect on microbial growth causing decreased cell concentration and partial cell autolysis
Solution Approach 1:
The patent implements periodic ethylamine feeding at controlled rates (0.5-2.0 g/L/h) rather than adding all at once. This periodic supplementation maintains adequate ethylamine concentration for L-theanine synthesis while preventing toxic accumulation that would inhibit microbial growth or cause cell autolysis
Solution Approach 2:
The patent uses feedback control by monitoring cell concentration and L-theanine production rate to adjust ethylamine feeding rate dynamically. When cell concentration decreases or L-theanine production slows, the feeding rate is adjusted to maintain optimal conditions without exceeding toxic thresholds
4Reliability
If conventional separation and extraction methods are used for L-theanine, then purification can be achieved, but a large number of acid/base reagents or flocculants are used and yield and product purity are low
Solution Approach 1:
The patent replaces conventional chemical separation methods (using acid/base reagents and flocculants) with membrane separation technology. This mechanical/physical separation method achieves high-purity L-theanine recovery without consuming large amounts of chemical reagents, improving both yield and product purity
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 results in a high yield of L-theanine with improved conversion rates, reduced by-product inhibition, and achieves high-purity L-theanine with a one-step crystallization yield of 72.3% and a purity of 99%, thereby addressing the cost and yield limitations of previous methods.
Implementation Method 1
Method for producing L-theanine via fermentation by a genetically engineered bacterium
Implementation Method 2
membrane separation techniques for efficient L-theanine production and purification
Implementation Method 3
achieves high-purity L-theanine with a one-step crystallization yield of 72.3% and a purity of 99%
Data Source
AI summary
The present invention belongs to the bioengineering field, and relates to a method for fermentation production of L-theanine by using an Escherichia coli genetically engineered bacterium. The engineered bacterium is obtained by serving a strain as an original strain, wherein the strain is obtained after performing a single copy of T7RNAP, a dual copy of gmas, xylR knockout, and sucCD knockout on an Escherichia coli W3110 genome, and by integrating genes xfp, pta, acs, gltA, and ppc, and knocking out ackA on the genome. The present invention has a high yield, and stable production performance; after 20-25 h, L-theanine has a titer of 75-80 g/L, and the yield is up to 52-55%. The fermentation broth is purified by membrane separation in combination with a cation-anion resin series technique. Moreover, the one-step crystallization yield is 72.3% and the L-theanine final product has a purity of 99%.