Recombinant Microorganisms for Thermodynamically Favorable Psicose Production
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Solution Overview
Problem
Current industrial methods for producing D-psicose are costly and thermodynamically unfavorable due to reversible reactions, leading to inefficient production and high costs for enzyme purification and product separation.
Innovation Solution
Genetic modifications in microorganisms, such as E. coli, including gene deletions and overexpression of specific enzymes like AlsE and HxpB, along with mutations in pathways like glycolysis and pentose phosphate pathways, enhance D-psicose production by making the process thermodynamically favorable and reducing competing pathways.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If in vitro enzymatic synthesis is used to produce D-psicose, then psicose can be produced through controlled enzymatic reactions, but the production efficiency is low and the cost of downstream separation and purification increases due to reversible reactions creating a mixture of glucose, fructose, and psicose
Solution Approach 1:
The patent extracts the psicose production pathway from the complex in vitro enzymatic system and transfers it into a living microorganism host (E. coli). By utilizing the organism's native metabolic machinery and transport systems, the method eliminates the need for external enzyme additions and simplifies product recovery, as psicose can be directly harvested from the culture medium without complex separation processes.
Solution Approach 2:
The patent introduces an intermediary phosphatase enzyme that catalyzes the dephosphorylation of psicose-6-phosphate to free psicose. This intermediary step is crucial because it converts the phosphorylated form (trapped inside cells) to the free form (excretable to medium), thereby mediating the transition from intracellular synthesis to extracellular accumulation and simplifying downstream purification.
2Quantity of substance
If the epimerization reaction from fructose to psicose is performed in vitro, then psicose can be produced, but the reaction is thermodynamically unfavorable with a predicted ΔG° of +5 KJ/mol, limiting production yield
Solution Approach 1:
The patent performs preliminary phosphorylation of fructose to fructose-6-phosphate before the epimerization reaction. This preliminary action changes the thermodynamic landscape of the subsequent epimerization, making it favorable. The phosphorylated intermediate (fructose-6-phosphate) serves as a better substrate for the epimerase enzyme, and the reaction proceeds more efficiently toward psicose-6-phosphate formation.
Solution Approach 2:
The patent changes the chemical parameters of the reaction system by working with phosphorylated sugar intermediates rather than free sugars. This parameter change (from free sugar to sugar phosphate) fundamentally alters the thermodynamics and kinetics of the epimerization reaction, making it proceed in the desired direction with higher yield. The phosphate group acts as a leaving group facilitator and stabilizes the transition state.
3Ease of manufacture
If glucose is converted to fructose via xylose-isomerase and then epimerized to psicose, then psicose production can be achieved, but costly enzyme purification and difficult feedstock separation are required, increasing production costs
Solution Approach 1:
The patent employs a self-service strategy where the microorganism host (E. coli) provides its own metabolic infrastructure for substrate uptake, conversion, and product excretion. The organism's native glucose transport systems, glycolytic enzymes, and psicose excretion mechanisms are harnessed to perform functions that would otherwise require external equipment and processes. This eliminates the need for separate enzyme purification and feedstock separation steps.
Solution Approach 2:
The patent merges multiple discrete biochemical steps (glucose transport, phosphorylation, epimerization, dephosphorylation, and psicose excretion) into a single integrated biological system. Rather than performing each step separately with isolated enzymes and purification steps, all transformations occur within the living cell, combining multiple functions into one unified manufacturing platform that simplifies 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
This approach significantly improves D-psicose yield and purity, facilitating industrial-scale production without the need for costly enzyme purification or difficult feedstock separation, thereby reducing production costs and enhancing efficiency.
Implementation Method 1
the epimerase is an allulose-6-phosphate 3-epimerase (AlsE)
Implementation Method 2
the phosphatase is a hexitol phosphatase B (HxpB)
Data Source
AI summary
The present disclosure relates to microorganisms useful in the biosynthesis of psicose. Also provided are methods of producing the disclosed microorganism and methods of producing psicose.