Secretory Expression by Pichia pastoris Simplifies Production of Immobilized D-Allulose 3-Epimerase: A Novel Strategy

The enzyme bottleneck

You don’t need another purification train. You need an enzyme that does the work before you touch it. A paper in Microbial Cell Factories (DOI: 10.1186/s12934-025-02763-4) shows exactly that.

Background: allulose needs a better enzyme route

D-allulose is produced by converting D-fructose using DPEase. That enzyme works, but producing it hurts.

Most DPEase comes from inside microbial cells. You grow the cells, lyse them, clarify the lysate, purify the enzyme, then immobilize it. Every step eats yield. The new study removes a significant chunk of that work.

What the study did

The team engineered Pichia pastoris to secrete DPEase into the culture medium. Since the enzyme exits the cell on its own, no cell lysis is needed. They combined purification with immobilization in one step. That is the key move.

Secretion simplifies the chain. You skip the lysis step. You skip a separate purification column. You go from clarified supernatant to an immobilized catalyst in one practical operation.

Then the researchers tested the enzyme. They measured stability across pH and temperature. They checked how often the immobilized enzyme could be reused. They also measured conversion from D-fructose.

Key findings

The data line up well for food applications.

Parameter	Result
pH stability (>80% relative activity)	5.0–11.0, optimum pH 6.0
Temperature stability (>80% relative activity)	35–70 °C, optimum 60 °C
Reuse	83.38% relative activity after 5 cycles
Conversion	17.03% maximum from 10% D-fructose

The enzyme holds up in a wide pH band. It holds up at typical food processing temperatures. And it still shows 83.38% activity after five batches. That last number matters more than the headline conversion.

What it means for manufacturers

Reusability drives enzyme cost. Five cycles at 83% means less frequent replacement. It also means fewer interruptions in a repeated-batch process. For a low-margin product like allulose, that is a real advantage.

The broad pH stability gives you flexibility. You don’t need precise pH control just to keep the enzyme alive. The 60 °C optimum also helps. Warmer reaction conditions reduce microbial load and improve fructose solubility.

For ingredient buyers, the production method matters. A secreted enzyme should cost less to make because it avoids expensive downstream processing. Ask suppliers about their expression system. Ask whether their immobilized DPEase comes from a clarified culture supernatant or from purified protein. The difference shows up in your quote.

Don’t treat 17.03% conversion as a yield ceiling. That’s a per-pass number. Manufacturers still need downstream separation. But a stable, reusable enzyme lowers the cost of each pass. That makes the overall economics more attractive.

Quick questions

Does 17.03% conversion mean I can skip chromatographic separation?

No. This is per-pass conversion from 10% D-fructose, not isolated yield. Allulose still needs to be separated from unreacted fructose. What the enzyme improves is the cost to run each pass.

Is Pichia pastoris acceptable for food enzyme production?

The strain used here is Pichia pastoris. Regulatory acceptance depends on your target market. Verify that the final enzyme preparation meets food-grade standards in the countries where you sell.

Should I switch to a secreted DPEase right away?

Run a trial first. Use your actual fructose stream and your process conditions. Look at productivity over multiple cycles, not just initial activity. Then decide.

The practical picture

This is not a flashy discovery. It’s a process engineering win. Secretion cuts steps, and cutting steps cuts cost. With immobilized DPEase still active after five uses, the path to cheaper allulose looks clearer. That’s worth attention from anyone buying or formulating with allulose enzymes.