Production, Purification, Characterization, and Safety Evaluation of a Constructed Recombinant D-Psicose 3-Epimerase

If you formulate with allulose, enzyme efficiency determines your raw material cost. This paper walks through a recombinant D-psicose 3-epimerase (DPEase) built for that job. The authors expressed the enzyme in E. coli, purified it, characterized its activity, and ran an acute safety study in rats. The result is a clear process snapshot, not just a lab curiosity.

Background

Allulose is a rare sugar. Manufacturers make it by converting fructose with epimerase enzymes. The trouble is that many enzymes work, but only a few work well enough for production. You need a DPEase with high specific activity, a sensible temperature range, and a safety profile you can defend. This study addresses all three.

What the study did

The team worked with a constructed recombinant DPEase. They expressed it in E. coli, then purified it. After purification, they measured the specific activity gain. Next, they ran bioconversion trials using 25% fructose as the substrate. They set the reaction at pH 7.5 and 55°C, with 10 mM Mn²⁺. To connect enzyme data to food use, they also tested the acute toxicity of a D-fructose-D-allulose mixed syrup in rats.

Key findings

The numbers are useful. After optimization, the purified enzyme’s specific activity increased 21.03-fold. That is a substantial purification gain. In the conversion test, allulose reached 5.60% concentration. The conversion rate came to 22.42%. Those figures come from a 25% fructose feed. The safety study showed no toxicity in rats.

Parameter	Result
Recombinant enzyme	DPEase expressed in E. coli
Purification outcome	Specific activity increased 21.03-fold
Substrate	25% fructose
Reaction pH	7.5
Reaction temperature	55°C
Metal cofactor	10 mM Mn²⁺
Allulose concentration	5.60%
Conversion rate	22.42%
Acute oral toxicity	No toxicity in rats

What it means for manufacturers

This is the kind of data that helps you ask better questions. The 21.03-fold purification improvement tells you the enzyme can be concentrated effectively. That matters for downstream processing and enzyme loading. The reaction conditions set expectations for your plant. A pH around 7.5 and a temperature of 55°C are workable. Manganese, however, is a process variable you need to manage. If your current system avoids metals, this enzyme may require a change.

The conversion rate is a starting point, not a ceiling. At 22.42%, a large portion of fructose remains. You will still need separation or another method to pull out the allulose. The safety data supports further evaluation. A mixed fructose-allulose syrup showed no acute toxicity in rats. That is useful, but it is not a substitute for a full food-use safety assessment. Ingredient buyers should treat this as a building block.

FAQ

What is D-psicose? D-psicose is another name for allulose. The enzyme DPEase converts fructose into D-psicose.

Why is 22.42% conversion important? With a 25% fructose substrate, about one-fifth of the sugar becomes allulose. That gives you a realistic benchmark for enzyme performance and downstream separation.

Can I use this enzyme in food production today? Not yet. The study demonstrates expression, purification, activity, and acute safety in rats. You still need scale-up validation, regulatory approval, and long-term stability data.

For now, this paper gives formulators a concrete reference. It connects an enzyme construct to a specific conversion result and a positive safety signal. That is exactly the kind of information you need before committing to an allulose process.