D-Allulose 3-Epimerase of Bacillus Origin Exhibits High Thermostability and Notable Catalytic Efficiency

A new workhorse for allulose production

Allulose formulators need enzymes that survive heat and heavy substrate loads. A newly characterized enzyme, DaeB, changes that picture. Researchers cloned it from Bacillus sp. KCTC 13219, a plant probiotic strain, and expressed it in Bacillus subtilis cells. The numbers are hard to ignore. DaeB held a 25-day half-life at 50°C. It turned over substrate at a kcat of 367 s⁻¹. In a conversion test, 700 g/L fructose produced about 200 g/L allulose.

Why epimerase thermostability matters

Allulose is a rare sugar with a clean sweet profile. Manufacturers make it by epimerizing fructose. The reaction depends on an enzyme called D-allulose 3-epimerase. Heat and high sugar concentrations stress these enzymes in industrial reactors. Thermostable enzymes reduce costs in several ways. They allow longer run times. They lower enzyme loading. They make it easier to run at temperatures that improve reaction speed and reduce viscosity. That is why a stable enzyme like DaeB attracts attention.

What the study did

The study started with a plant probiotic strain, Bacillus sp. KCTC 13219. The team isolated the gene for a new epimerase, named DaeB, and moved it into Bacillus subtilis for expression. The work appeared in Microbial Cell Factories under DOI 10.1186/s12934-021-01550-1. They then tested the enzyme’s stability and activity. A 50°C incubation gave a half-life of 25 days. Kinetic analysis showed a kcat of 367 s⁻¹. For practical production, they fed 700 g/L fructose to the enzyme. The reaction produced roughly 200 g/L allulose. The authors point to large-scale production as a promising application.

Key findings at a glance

Production challenge	DaeB result
Enzyme losing activity at process temperature	25-day half-life at 50°C
Slow turnover	kcat = 367 s⁻¹
Need to work with concentrated fructose	700 g/L fructose converted
Product concentration for recovery	~200 g/L allulose

What this means for manufacturers

This enzyme fits the profile for industrial allulose production. The 25-day half-life at 50°C is outstanding. Many reactors need frequent enzyme additions if the catalyst degrades. DaeB does not. The high kcat also points to fast throughput. A short contact time helps plants that process large volumes.

The yield from concentrated fructose matters for downstream processing. Starting with 700 g/L fructose and hitting about 200 g/L allulose gives a clear concentration for recovery. Less water means lower evaporation costs. Formulators and ingredient buyers should ask their enzyme suppliers whether DaeB is available for trials. It is not a laboratory curiosity. It is a practical candidate.

FAQ

Which strain does DaeB come from? Bacillus sp. KCTC 13219. It is a plant probiotic strain. Researchers expressed the enzyme in Bacillus subtilis, a common industrial host.

Why is the 25-day half-life important? At 50°C, half of the enzyme remains active after 25 days. That gives production teams a wide operating window. It cuts enzyme replacement frequency and supports longer continuous runs.

What yield should formulators expect? In the study, 700 g/L fructose produced around 200 g/L allulose. That is not a theoretical calculation. It came from a real substrate conversion test.

Put it on your radar

DaeB is one of the more practical epimerases to come out recently. It has thermal endurance, fast kinetics, and a strong product concentration. The enzyme comes from a plant probiotic Bacillus strain and expresses in a widely used industrial host. If you are sourcing allulose biocatalysts, ask for data on DaeB. The science is solid. The next step is scale-up.