Inducible Large Plasmid Replication for High-Yield Low-Mutation Production

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Solution Overview

Problem

Existing methods for producing large plasmids, such as bacterial artificial chromosomes (BACs), face challenges in achieving high yields while maintaining vector quality due to metabolic burdens on bacterial cells, leading to increased mutation frequencies.

Innovation Solution

A method involving the use of an inducible origin of replication (ori) in bacterial cells, where replication is initiated only after reaching a specific optical density (OD600 of at least 20), combined with inducers like IPTG, temperature shifts, and inhibitors like chloramphenicol, to minimize metabolic stress and enhance yield and quality.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high copy number plasmids are used to increase yield, then plasmid production per cell increases, but metabolic burden on bacterial cells increases leading to reduced quality and increased mutation frequencies

Engineering Contradiction:

Improveplasmid production yieldVSAvoidplasmid quality and mutation frequency

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies preliminary action by allowing bacterial cells to reach high optical density (OD600 ≥ 20) and accumulate sufficient biomass before inducing plasmid replication. This preliminary growth phase ensures cells have adequate metabolic resources to handle high copy number replication without excessive stress, thereby maintaining plasmid quality while achieving high yields.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs dynamics by using an inducible origin of replication system that allows the plasmid copy number to be dynamically controlled. The system transitions from low copy number during the growth phase to high copy number after induction with IPTG, enabling optimization of both cell growth and plasmid production at different stages of the fermentation process.

Inventive Principle:

Principle #15Dynamics

2Loss of time

If plasmid replication is induced early in bacterial growth, then replication starts sooner, but bacterial cells experience high metabolic burden leading to reduced plasmid quality

Engineering Contradiction:

Improvetime to start replicationVSAvoidplasmid quality

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The patent uses preliminary action by delaying plasmid replication induction until bacterial cells have reached high optical density (OD600 ≥ 20). This ensures cells have accumulated sufficient metabolic resources and biomass before initiating high copy number replication, preventing metabolic stress that would compromise plasmid quality while still achieving rapid production after induction.

Inventive Principle:

Principle #10Preliminary action

3Quantity of substance

If large scale cultures are used to obtain substantial amounts of BAC, then yield increases, but process complexity and cost increase

Engineering Contradiction:

Improveamount of BAC producedVSAvoidculture scale and process complexity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent applies parameter changes by optimizing the induction timing parameter (OD600 ≥ 20) and using an inducible origin system that enables high copy number amplification. This allows substantial amounts of BAC to be produced in scaled-up cultures without proportionally increasing process complexity, as the same induction protocol can be applied across different culture scales.

Inventive Principle:

Principle #35Parameter changes

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 high-quality, pharmaceutical-grade large plasmids to be produced at high yields (up to 120 mg/L) with reduced mutation frequencies, suitable for DNA-based vaccines, and is scalable to large volumes.

Implementation Method 1

adding one or more inducers of said inducible origin of replication to the culture medium

Methodology Applied

Scientific EffectInduction:

Implementation Method 2

culturing the bacterial cells in the culture medium until an optical density at 600 nm (OD600) of at least 20 is reached

Methodology Applied

Scientific EffectOptical density measurement: Absorption (EM radiation)

Implementation Method 3

adding an inhibitor of bacterial protein synthesis to the culture medium after the one or more inducers of said inducible origin of replication has been added

Methodology Applied

Scientific EffectInhibition of protein synthesis:

Data Source

PatentUS12570990B2Large vectors and methods for high-yield production

Publication Date: 2026.03.10 KATHOLIEKE UNIV LEUVEN

AI summary

Provided herein are methods for the production of a vector with a size of at least 16 kb from bacterial cells comprising the consecutive steps of a) obtaining bacterial cells comprising a vector with a size of at least 16 kb, comprising an inducible origin of replication, b) inoculating culture medium with the bacterial cells comprising the vector, c) culturing the bacterial cells in the culture medium, d) adding one or more inducers of said inducible origin of replication to the culture medium when the bacterial culture has reached an optical density at 600 nm (OD600) of at least 20, e) further culturing the bacterial cells in the culture medium, f) optionally separating the bacterial cells from the culture medium, and g) recovering the plasmid from the bacterial cells. Also provided herein are vectors with a size of at least 16 kb comprising an inducible origin of replication for use in such methods.