A Bacillus-Origin D-Allulose 3-Epimerase Shows Strong Thermostability and Notable Catalytic Activity

Allulose formulators are always hunting for enzymes that survive production conditions. This paper points to one worth watching. Researchers cloned a new D-allulose 3-epimerase—called DaeB—from Bacillus sp. KCTC 13219 and expressed it in Bacillus subtilis. The enzyme turned in numbers that should grab any ingredient buyer’s attention: a 25-day half-life at 50°C and a kcat of 367 s⁻¹.

Why this enzyme stands out

Allulose is a rare sugar with about 70% of the sweetness of sucrose and almost no calories. The bottleneck is manufacturing. Most processes rely on ketose 3-epimerases that convert fructose to allulose, but many of those enzymes are not stable enough for repeated industrial use. Heat, pH shifts, and high substrate loads wear them out quickly.

DaeB comes from a plant-associated Bacillus strain. That origin matters. The strain was already known for probiotic qualities, but the enzyme itself turned out to be unusually hardy. When expressed in Bacillus subtilis, it didn't just fold correctly. It performed better than many previously described allulose epimerases.

What the study did

The team cloned the daeB gene from Bacillus sp. KCTC 13219. They then expressed it in Bacillus subtilis cells, a host that food producers already use for enzyme manufacturing. That is a practical choice. It avoids the endotoxin concerns that come with E. coli expression systems.

After purification, they characterized the enzyme’s activity and stability. They also tested its ability to convert high-concentration fructose into allulose. The substrate load they chose—700 g/L fructose—mirrors what an industrial process might actually use. That is not a typical lab-scale condition. It's a production-scale reality check.

Key findings

DaeB is a robust catalyst. At 50°C, it held a half-life of 25 days. That kind of thermal stability means longer run times, fewer enzyme refills, and lower processing costs. Its catalytic rate, kcat of 367 s⁻¹, also puts it in a high-performing class.

The conversion test was equally promising. Starting with 700 g/L fructose, DaeB produced roughly 200 g/L allulose. That yield is meaningful because concentrated feeds reduce downstream evaporation costs.

Here is a quick look at the numbers:

Parameter	DaeB result	Why it matters
Half-life at 50°C	25 days	Long operating window for continuous or repeated-batch bioconversion
Catalytic rate (kcat)	367 s⁻¹	Fast turnover means less enzyme needed per kilo of product
Substrate concentration	700 g/L fructose	Closer to real-world high-solids conditions
Allulose produced	~200 g/L	Attractive yield from a concentrated feed

The paper also reports that DaeB has "great potential" for large-scale production. That phrasing is cautious, but the data supports it.

What it means for manufacturers

For formulators, the takeaway is practical. If this enzyme scales up successfully, it could reduce enzyme dosing and make continuous processing more feasible. That is especially relevant for producers who want to make allulose at food-grade scale without paying for constant enzyme replacement.

The choice of expression host is also good news. Bacillus subtilis is already established in food enzyme production. That lowers some regulatory and technical risk. You are not relying on an exotic expression platform to make the enzyme.

Still, this is one study. The work was done at lab and bench scale. Pilot-scale runs, purification economics, and regulatory approvals remain ahead. But the stability profile alone justifies putting this enzyme on your radar.

FAQ

Is DaeB the same as other allulose epimerases? No. It is a newly cloned enzyme from a specific Bacillus strain. Its thermostability and catalytic activity are distinct from many earlier described epimerases.

Does this mean allulose production will get cheaper soon? Not automatically. The enzyme is promising, but commercial adoption depends on scale-up results, enzyme production costs, and regulatory status. That said, a 25-day half-life could meaningfully improve process economics.

Can I use DaeB in my product today? You should treat this as a development-stage enzyme. The research shows strong potential, but food-grade availability and regulatory approval have not been confirmed in this paper.

Closing thoughts

DaeB is not just another epimerase. It combines long-term thermal stability, high turnover, and good performance under concentrated fructose loads. For anyone working on allulose production, that combination is rare. Watch for scale-up data. The enzyme may soon justify a closer look.