Construction of an Ultra-Thermostable D-Allulose 3-Epimerase Using Arthrobacter globiformis M30

Thermostability is the silent bottleneck in enzymatic sugar conversion. If your epimerase dies at 70°C, your whole process runs at that temperature. That costs you time, enzyme, and money. A recent paper in FEBS Open Bio (DOI: 10.1002/2211-5463.70060) takes direct aim at that bottleneck. The target: a better enzyme for D-allulose production.

The problem with current epimerases

D-allulose is a rare sugar with nearly zero calories and about 70% of sucrose’s sweetness. It’s made by isomerizing D-fructose using D-allulose 3-epimerases (DAEs). The reaction is reversible, and the equilibrium favors fructose over allulose. Heat helps shift that equilibrium. Higher temperatures also reduce viscosity and lower the risk of microbial contamination.

Most DAEs don’t handle heat well. They lose activity within hours at moderate temperatures. That’s why the industry keeps pushing for thermostable variants. More stability means higher substrate loading, fewer enzyme refills, and cleaner downstream processing. It also simplifies reactor cleaning and enzyme recovery.

What the study did

The researchers started with a D-allulose 3-epimerase from Arthrobacter globiformis M30 (AgDAE). They engineered a chimeric mutant, called mutant E, by swapping structural elements to combine favorable traits from related enzymes. The goal was simple. Keep the catalytic core, improve the heat tolerance.

The result is a mutant that performs in a completely different temperature league.

Key findings

The headline number is straightforward: mutant E stays highly functional above 95°C. It also remains stable below 80°C. That’s a massive operational window for an enzyme that most people would expect to denature long before boiling point.

Property	Wild-type AgDAE	Chimeric mutant E
Functional temperature	Not heat-tolerant	Above 95°C
Stability range	Limited at elevated temperatures	Stable below 80°C
kcat on D-fructose	Baseline	More than 2× wild-type
Catalytic efficiency (kcat/Km)	Baseline	Improved

The kcat jump matters. Mutant E’s kcat for D-fructose is more than twice the wild-type value. It’s not just a tougher enzyme. It’s a faster one. The catalytic efficiency gain means you get more allulose per unit of enzyme.

Here’s the industrial context. Matsutani Chemical Industry already scaled up D-allulose production using AgDAE enzymes. Their commercial system runs under the Astraea brand. This new mutant builds on the same enzyme family, but pushes the temperature ceiling much higher.

What it means for manufacturers

Higher operating temperature changes process economics. Run the isomerization at 80–95°C instead of 50–60°C, and you get faster kinetics, better fructose solubility, and fewer bioburden problems. The enzyme itself lasts longer under those conditions. That combination is rare.

For ingredient buyers, this also matters. A more efficient epimerase means lower enzyme cost per kilogram of allulose. That could feed through to ingredient pricing over time. And if the enzyme stays stable below 80°C, formulators gain real flexibility in reactor design and cleaning cycles.

One caveat. The paper reports lab-scale results. Scale-up validation and food-grade regulatory approvals still lie ahead. But the direction is clear. Enzyme engineering is moving allulose production toward hotter, faster, cheaper processes.

FAQ

Why does thermostability matter so much for allulose production? Because heat drives the equilibrium toward allulose and speeds up the reaction. A thermostable enzyme lets you operate at higher temperatures without denaturation.

Is mutant E ready for commercial use? Not yet. It’s a research-stage result. The commercial Astraea system uses the AgDAE enzyme family, not this specific mutant.

What’s the practical temperature range? Mutant E functions above 95°C and stays stable below 80°C. The operating sweet spot likely sits somewhere in that window, depending on your reactor setup.

The gap between lab enzyme and commercial reality is always wide. But a mutant that doubles catalytic activity while surviving 95°C is exactly the kind of step change that closes that gap. Watch this space.