Microbial HMO Export Engineering for High-Purity Oligosaccharides
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Solution Overview
Problem
Current fermentation processes for producing complex human milk oligosaccharides face challenges in efficiently exporting larger oligosaccharides from bacterial cells, leading to unwanted mixtures with precursor oligosaccharides and limited large-scale production capabilities.
Innovation Solution
Genetically modify microbial host cells to enhance the expression of recombinant glycosyltransferases and modify endogenous sugar export proteins, using secondary active transporters to increase the export of desired oligosaccharides into the culture medium, while inhibiting the export of precursors, thereby facilitating the production and recovery of complex oligosaccharides like lacto-N-triose II and lacto-N-tetraose.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional fermentation processes are used to produce complex HMOs, then production of simpler HMOs is achieved, but export of oligosaccharides and productivity are limited
Solution Approach 1:
The patent modifies the export capacity parameter of the microbial cell by introducing heterologous oligosaccharide exporters and modifying endogenous ones. This changes the transport parameters to enable efficient export of complex HMOs (tetra-, penta-, hexasaccharides) that were previously retained inside cells, directly resolving the contradiction between production capability and export limitation
Solution Approach 2:
The patent employs a multi-functional approach by combining several exporter proteins (MFS-type and ABC-type transporters) with different substrate specificities in the same microbial host. This universal export system handles various HMO sizes and structures simultaneously, enabling the cell to export both simple and complex oligosaccharides efficiently, thus improving overall productivity across the entire HMO product range
2Productivity
If oligosaccharide export is enhanced to improve productivity, then desired oligosaccharides are exported, but unwanted precursor oligosaccharides are also exported
Solution Approach 1:
The patent applies local quality by selecting and engineering exporters with specific substrate recognition characteristics. Different exporter proteins are chosen based on their ability to selectively transport particular HMO structures. By matching exporter specificity to the desired product structure, the system achieves selective export of target HMOs while minimizing precursor contamination, thus resolving the purity-productivity contradiction
Solution Approach 2:
Instead of trying to prevent precursor export through metabolic control, the patent inverts the approach by using exporters that have higher affinity or specificity for the complex desired HMO products. This selective export mechanism naturally prioritizes the export of larger, more complex oligosaccharides over their smaller precursors, achieving both high productivity and product purity simultaneously
3Ease of manufacture
If microbial engineering is used to produce complex HMOs, then production capability is improved, but export capability becomes the limiting factor
Solution Approach 1:
The patent segments the export function by introducing multiple distinct exporter proteins rather than relying on a single transporter. Different exporters (MFS-type and ABC-type) are assigned to handle different molecular weight classes of HMOs. This segmentation of the export function eliminates the bottleneck that would exist with a single general-purpose transporter, enabling efficient production and export of complex HMOs simultaneously
Solution Approach 2:
The patent uses oligosaccharide exporters as intermediary proteins that mediate the transfer of complex HMOs from the intracellular production site to the extracellular medium. These intermediary transporters bridge the gap between the metabolic engineering achievements (intracellular synthesis capability) and the practical production requirement (extracellular recovery), resolving the contradiction between manufacturing capability and productivity
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
Enables the production of complex human milk oligosaccharides, such as lacto-N-triose II and lacto-N-tetraose, in large quantities by enhancing their export into the culture medium, overcoming the limitations of existing fermentation processes and achieving pure, high-yield production.
Implementation Method 1
The E. coli lactose permease LacY probably represents the most intensively characterized solute transporter... transporting sugars, drugs, hydrophobic molecules, peptides, organic ions, etc. by uniport, symport or antiport
Implementation Method 2
ion-gradient-driven transport systems have the potential to translocate solutes in both directions across the membrane... exploiting metabolic energy like ATP or the electrochemical potential
Implementation Method 3
Classically energy-driven active transporters perform substrate movement against its concentration or electrochemical gradient... pumps can be principally divided into primary active and secondary active transporters
Data Source
AI summary
The present invention relates to methods for the production of oligosaccharides in genetically modified bacterial host cells, as well as to the genetically modified host cells used in the methods. The genetically modified host cell comprises at least one recombinant glycosyltransferase, and at least one nucleic acid sequence coding for a protein enabling the export of the oligosaccharide.