Segmented Plasmid System for Sucrose-Assimilating E. coli
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Solution Overview
Problem
It is challenging to simultaneously impart the ability to assimilate sucrose and produce isopropyl alcohol to Escherichia coli, as the large DNA size required exceeds the capacity of plasmid vectors, leading to difficulties in stable gene introduction and industrial suitability.
Innovation Solution
An isopropyl alcohol-producing Escherichia coli strain is developed by incorporating a sucrose hydrolase gene from the sucrose non-PTS gene group, along with genes encoding enzymes for acetoacetate decarboxylase, isopropyl alcohol dehydrogenase, CoA transferase, and thiolase activities, derived from various bacterial sources, to enable efficient sucrose assimilation and isopropyl alcohol production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If all genes for sucrose assimilation and isopropyl alcohol production are introduced into E. coli, then the bacterium can produce isopropyl alcohol from sucrose, but the total DNA size exceeds plasmid vector capacity
Solution Approach 1:
The patent divides the large DNA construct into two separate plasmid vectors: pGAP-cscA (containing sucrose hydrolase gene) and pACYC-IPA (containing isopropyl alcohol production genes). This segmentation allows each plasmid to remain within the 10,000 bp capacity limit while collectively providing both sucrose assimilation and isopropyl alcohol production capabilities.
Solution Approach 2:
The patent combines two separate plasmid vectors into a single bacterial system (E. coli B strain). The two plasmids work together synergistically: pGAP-cscA provides sucrose hydrolysis capability while pACYC-IPA provides the isopropyl alcohol production pathway, achieving the overall function that would require excessive DNA size in a single construct.
2Device complexity
If two kinds of plasmid vectors are used to reduce DNA size, then plasmid capacity limit is satisfied, but plasmids are eliminated during repetitive growth
Solution Approach 1:
The patent assigns different functional roles to each plasmid with optimized characteristics: pGAP-cscA uses a strong constitutive promoter (GAP promoter) to ensure stable expression of sucrose hydrolase, while pACYC-IPA uses the pACYC184 origin of replication known for high copy number and stability. Each plasmid's local qualities are tailored to its specific function and stability requirements.
Solution Approach 2:
The patent introduces a selection marker system as an intermediary mechanism to maintain plasmid stability. Ampicillin resistance marker on pGAP-cscA and chloramphenicol resistance marker on pACYC-IPA serve as selective pressures that prevent plasmid loss during repetitive growth, allowing the bacteria to maintain both plasmids without continuous antibiotic exposure being required.
3Reliability
If continuous antibiotic exposure is used to maintain plasmids, then plasmid elimination is prevented, but production cost increases
Solution Approach 1:
The patent incorporates selection markers (ampicillin resistance and chloramphenicol resistance genes) into the plasmid structures during construction. This preliminary action embeds the stability mechanism directly into the plasmids, allowing them to maintain themselves through selective pressure only when needed (during initial transformation and maintenance phases), rather than requiring continuous antibiotic exposure throughout the entire production process.
Solution Approach 2:
The patent uses inexpensive antibiotic resistance markers as temporary selection tools during plasmid establishment and maintenance phases. Once the plasmids are stably integrated into the bacterial population, the antibiotics can be removed from the medium, and the plasmids are maintained through their intrinsic stability mechanisms (origin of replication and selection pressure from previous generations), eliminating the need for continuous expensive antibiotic addition during large-scale production.
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 allows for the efficient production of isopropyl alcohol from sucrose, overcoming the limitations of large DNA size and catabolite repression by glucose, thereby providing a cost-effective and industrially viable method for isopropyl alcohol production.
Implementation Method 1
a sucrose non-PTS gene group, and an imparted or enhanced isopropyl alcohol production system
Implementation Method 2
genes encoding enzymes for acetoacetate decarboxylase, isopropyl alcohol dehydrogenase, CoA transferase, and thiolase activities
Implementation Method 3
genes encoding enzymes for acetoacetate decarboxylase, isopropyl alcohol dehydrogenase, CoA transferase, and thiolase activities
Data Source
AI summary
The present invention provides an isopropyl alcohol-producing Escherichia coli that includes at least a sucrose hydrolase gene that belongs to a sucrose non-PTS gene group, and an imparted or enhanced isopropyl alcohol production system, and an isopropyl alcohol production method of producing isopropyl alcohol from a sucrose-containing plant-derived raw material using the isopropyl alcohol-producing Escherichia coli.