Engineering, Expression, and Immobilization of Epimerases for D-Allulose Production

Why this review matters

D-allulose is a potential replacement for sucrose, and formulators are paying attention. The real problem sits upstream: the enzyme that makes D-allulose has to be stable enough, cheap enough, and reusable enough for industrial production. A review in the International Journal of Molecular Sciences (DOI: 10.3390/ijms241612703) looks at exactly that problem. It covers three ways researchers are turning DAEase into a practical production tool.

Background

DAEase is not one single enzyme. The review highlights three newly identified DAEases with properties suited to industrial D-allulose production. Natural epimerases often fail under real process conditions. Heat and acidity damage the enzyme, and that eats into yield.

So the field has moved on three fronts. Enzyme engineering improves thermostability or acid tolerance. Bacillus subtilis offers a microbial host for biosynthesis. Immobilization keeps the enzyme active longer. Each approach matters, but the real value comes from combining them.

What the review covers

The first front is enzyme engineering. Work on DAEase has focused on making it resist process stress. A more thermostable enzyme runs longer before it denatures. An acid-tolerant enzyme survives contact with fructose syrups that would otherwise shorten its life.

The second front is expression. Using Bacillus subtilis for D-allulose biosynthesis changes how the enzyme is produced. The production host decides the cost of the enzyme, and Bacillus subtilis is a practical choice for the kind of enzyme loads manufacturers need.

The third front is immobilization. Fixing DAEase to a support improves its activity, half-life, and stability. That changes the enzyme from a consumable that gets thrown away into a reusable catalyst. For a producer, that is a direct cost advantage.

Key findings

The most concrete result in the review comes from a 5-liter fed-batch bioreactor. After 64 hours, the culture produced 74.2 grams of D-allulose per liter. The yield was 0.93 grams of allulose per gram of D-fructose. That number matters. It means very little fructose goes to waste.

Process lever	What the work did	Why it matters for production
Enzyme engineering	Improved heat tolerance and acid tolerance in DAEase	Keeps the enzyme active under process stress
Expression host	Used Bacillus subtilis for D-allulose biosynthesis	Lowers enzyme production and purification cost
Immobilization	Improved DAEase activity, half-life, and stability	Allows enzyme reuse and longer operation

The review treats these levers as a system. A highly engineered enzyme still needs a good host. An immobilized enzyme still needs enough native activity. The 5L bioreactor result shows the combination working outside a test tube.

What it means for manufacturers

Ingredient buyers should watch this work closely. Enzyme stability and reuse are the two variables that move allulose pricing. The 0.93 g/g yield also reduces raw material cost. Buy less fructose, make the same amount of allulose. That is the kind of math procurement teams want to see.

Formulators gain supply confidence. When producers can run longer or continuously, batch-to-batch variation drops. The review does not promise a commercial process exists today. It does show that the pieces for one are already on the table.

FAQ

What is DAEase?

The review uses DAEase as shorthand for the epimerase that converts D-fructose into D-allulose. It is the key biocatalyst in this production route.

How much allulose did the optimized process produce?

The 5-liter fed-batch bioreactor reached 74.2 g/L after 64 hours, with a yield of 0.93 g/g D-fructose.

Why does immobilization matter?

Immobilization improves enzyme activity, half-life, and stability. That means manufacturers can reuse the enzyme, which directly cuts production cost.

Closing thoughts

Enzyme technology is moving fast. The combination of better DAEase variants, Bacillus subtilis expression, and immobilization design gives producers a realistic route to cost-effective D-allulose. Suppliers who follow this research will know which processes deserve a second look.