Secretion by Pichia pastoris Simplifies Production of Immobilized D-Allulose 3-Epimerase: A New Strategy

The Enzyme Bottleneck in Allulose Production

Enzyme cost can make or break an allulose project. D-allulose 3-epimerase (DPEase) converts fructose into allulose. But purifying and immobilizing that enzyme adds cost. A new study (DOI: 10.1186/s12934-025-02763-4) tackles that bottleneck with a straightforward move: use Pichia pastoris secretion to stream production.

Why DPEase Production Is Cumbersome

DPEase usually lives inside cells. That means you have to break cells open, separate the enzyme from cell debris, and then attach it to a support. Each step adds time and enzyme loss. Secretion changes the picture. When the host microbe pumps DPEase into the culture medium, the first step disappears. The study shows a one-step purification and immobilization route built on that advantage.

What the Study Did

The researchers expressed a recombinant DPEase in Pichia pastoris. The host secreted the enzyme into the broth. They then moved from that broth to an immobilized enzyme preparation in one step. Next, they evaluated the enzyme's stability and its ability to convert D-fructose to D-allulose.

They tested pH across a wide span. They tested temperature across a practical span. They also ran repeated batches to see how well the immobilized enzyme held up. The reaction used 10% D-fructose as substrate.

Key Findings

The immobilized enzyme showed a wide working window. It stayed above 80% relative activity from pH 5.0 to 11.0. It stayed above 80% relative activity from 35°C to 70°C. The optimum sat at pH 6.0 and 60°C.

Reuse data look commercially promising. After five uses, the enzyme still kept 83.38% relative activity. At 10% fructose, the maximum D-allulose conversion reached 17.03%.

Parameter	Result
Relative activity after 5 reuses	83.38%
pH stability range	5.0–11.0 (>80% relative activity)
Temperature stability range	35–70°C (>80% relative activity)
Optimum pH	6.0
Optimum temperature	60°C
Maximum conversion from 10% D-fructose	17.03%

What This Means for Manufacturers

The commercial story is fewer unit operations. Secretory expression removes cell disruption. One-step purification and immobilization removes a separate purification step. That should shorten enzyme production cycles and reduce capital demands.

For formulators, the broad pH and temperature tolerance is a relief. You can run the reaction at pH 6.0 and 60°C without tight process control. The enzyme can tolerate excursions outside those optima and still maintain high activity. Five reuses at 83.38% means you can spread enzyme cost across several batches. That changes the enzyme cost per kilogram of allulose.

The 17.03% conversion at 10% fructose gives a process benchmark. The study does not report higher fructose concentrations. Scale-up trials will need to test whether the enzyme keeps that conversion at commercially typical sugar loads.

Frequently Asked Questions

How many times can the immobilized enzyme be reused?

The study reports five reuses with 83.38% relative activity. That is the furthest data point provided.

What conditions does the enzyme prefer?

The optimum pH is 6.0 and the optimum temperature is 60°C. The enzyme maintains over 80% relative activity from pH 5.0 to 11.0 and from 35°C to 70°C.

Why does secretion by Pichia pastoris matter?

Because the enzyme ends up in the culture medium, not inside the cells. This allows one-step purification and immobilization. You avoid cell lysis, debris removal, and multiple recovery steps.

The next step is pilot-scale testing. If this system works with commercial fructose streams, it could simplify allulose economics. The pieces are here: a stable enzyme, a reusable support, and a host organism that secretes the catalyst. That is a useful combination for anyone planning an allulose line.