Production of D-Allulose from D-Fructose Using Permeabilized Recombinant Corynebacterium glutamicum Cells

The research in one paragraph

If you are evaluating bulk allulose production, you know the enzyme route comes with trade-offs. This study proposes a whole-cell alternative. Researchers used permeabilized recombinant Corynebacterium glutamicum cells to convert D-fructose into D-allulose. The enzyme came from Flavonifractor plautii. The reaction was fast. The product concentration was high.

Why the host matters

E. coli is a common lab workhorse. But it is not GRAS. For food additive production, that creates problems. You need extra purification. You may face regulatory pushback. C. glutamicum, in contrast, has a long safe history in amino acid production. It is GRAS. That makes it a more acceptable host for making a rare sugar.

The researchers did not just express the epimerase. They permeabilized the cells. Permeabilization makes the cell membrane porous. Substrate and product can move in and out. The enzymes stay inside. This gives you the convenience of a soluble catalyst without lysing the cells or purifying the enzyme.

What the study did

The team engineered C. glutamicum to express D-allulose 3-epimerase from Flavonifractor plautii. They tested the permeabilized cells for conversion of D-fructose. Then they optimized reaction conditions. The key result comes from a high substrate load: 750 g/L D-fructose. With 10 g/L permeabilized cells, the reaction produced 235 g/L D-allulose in 40 minutes.

The conversion yield was 31%. Volumetric productivity reached 353 g/L/h. Those are not incremental numbers. They show a practical balance between yield and throughput.

Key numbers at a glance

Parameter	Result
Substrate	750 g/L D-fructose
Biocatalyst loading	10 g/L permeabilized cells
Reaction time	40 minutes
Product	235 g/L D-allulose
Conversion yield	31%
Volumetric productivity	353 g/L/h

The reaction time matters. At 40 minutes, a batch process can turn around quickly. The high product concentration also matters. At 235 g/L, downstream concentration work is much smaller than it would be with a dilute reaction stream.

What this means for food formulators and buyers

For an ingredient buyer, this process has one obvious appeal: it avoids E. coli. Using a GRAS host shortens the distance between fermentation and food-grade status. That does not mean the process is immediately commercial. Scale-up would need validation. But the proof of concept is directly relevant to allulose supply.

For formulators, the 31% conversion sets the separation challenge. The value is in the final titer and productivity. A high final allulose concentration means less energy spent on water removal. A fast reaction time means better reactor utilization. Both affect cost per kilogram.

This also points toward a production model that uses whole cells instead of purified enzyme. Permeabilized cells are simpler to make. They keep the enzyme in a natural environment. For a manufacturer, that could lower biocatalyst cost and improve processing economics. Stability data would be the next step before commercial decisions.

FAQ

Why not use E. coli for allulose production? E. coli is not a GRAS organism. For food additives, using it requires more extensive purification and regulatory justification. C. glutamicum is already accepted in food-grade fermentation.

What does “permeabilized” mean in this context? The cells are treated so their membranes allow small molecules like fructose and allulose to pass. The enzymes remain inside the cells. The cells work like tiny bags full of catalyst.

Can this process handle a high fructose load? Yes. The study used 750 g/L D-fructose. In 40 minutes, 10 g/L of permeabilized cells produced 235 g/L D-allulose. That is a 31% conversion rate.

No full commercial recipe exists yet. But this work answers a real question: can a GRAS host produce allulose at high concentration without enzyme purification? The answer is yes. That is worth watching.