Construction of a Hyperthermostable D-Allulose 3-Epimerase Using Arthrobacter globiformis M30

The Enzyme Story

D-allulose keeps finding its way into more formulations. Every gram of it starts with an enzyme that can flip D-fructose into D-allulose. That enzyme is D-allulose 3-epimerase, and a well-known version comes from Arthrobacter globiformis. Researchers now report a chimeric mutant, called mutant E, that behaves far better at high temperature. The work appears under DOI 10.1002/2211-5463.70060.

This matters. Heat tolerance is not a small feature in sugar production. Enzymes that fall apart at moderate temperatures force manufacturers to slow down, use more enzyme, and cool down big reactors. A hyperthermostable variant changes the math.

Background

D-allulose is a rare sugar with almost no calories. It has become attractive to food and beverage formulators looking for bulk and sweetness without the glycemic load. The industrial route to D-allulose typically relies on enzymatic epimerization of D-fructose. The enzyme used in that process needs to be active, selective, and stable under real process conditions.

This paper focuses on AgDAE, the D-allulose 3-epimerase from Arthrobacter globiformis strain M30. Matsutani Chemical Industry already used this enzyme to develop a scalable D-allulose production system and commercialized it under the brand name Astraea. So this is not a lab-only enzyme. It is already an industrial asset.

What the study did

The researchers used protein engineering to build a chimeric mutant derived from AgDAE. They named it mutant E. Their goal was direct: make the enzyme more thermostable while preserving or improving its activity on D-fructose.

The team then compared mutant E with the wild-type enzyme. They measured kinetic parameters. They also tested thermal behavior. The results are clear.

Key findings

Mutant E keeps working at temperatures above 95°C. That is hot. Most enzymes would be denatured quickly at that point. Mutant E also stays stable below 80°C. That gives a wide operating window for production. The kinetic improvement is just as noticeable. For D-fructose, its kcat value is more than double that of wild-type AgDAE. Catalytic efficiency, expressed as kcat/Km, also improved.

The table below puts those changes in context.

Parameter	Wild-type AgDAE	Mutant E
kcat for D-fructose	Reference value	More than 2× wild-type
Catalytic efficiency (kcat/Km)	Baseline	Improved
Activity above 95°C	Not reported	High functionality retained
Stability below 80°C	Not reported	Stable

The exact numbers matter less than the direction. More activity. More heat tolerance. That combination is exactly what process engineers want to see in a biocatalyst.

What it means for manufacturers

For ingredient buyers and formulators, this points toward a future where D-allulose can be made at higher temperatures, with less enzyme, and possibly at lower cost. The commercial relevance is already proven in one sense: AgDAE is the enzyme behind Astraea, an existing scaled production system. A hyperthermostable version of the same enzyme line could make that system even more efficient.

Heat-tolerant enzymes are easier to handle in industrial reactors. They tolerate process fluctuations. They can run at temperatures that discourage microbial contamination. They also open the door to reusing the enzyme for more cycles. All of that lowers production costs, and lower production costs eventually show up in ingredient pricing and supply security.

None of this means mutant E is already in a commercial product. The paper describes construction and lab-scale evidence. Scale-up takes time. But for anyone buying D-allulose, this is the kind of development that matters.

FAQ

Is mutant E already used in commercial D-allulose production?

Not according to this paper. The study describes a chimeric mutant with promising thermostability and kinetic properties. Commercialization is not claimed.

How much more active is mutant E?

Its kcat for D-fructose is more than twice that of wild-type AgDAE. Catalytic efficiency also improved.

Why does thermostability matter for D-allulose?

Higher temperatures allow faster reactions and better substrate handling. A stable enzyme can also survive longer in a reactor, which cuts enzyme usage and cost.

The bigger picture

D-allulose demand is growing. Process improvements in the enzyme step have direct consequences for everyone downstream. A hyperthermostable mutant E is not just an incremental lab result. It is a signal that the biocatalyst behind D-allulose can be pushed harder. Formulators should watch this line of work closely.