Experts have found a way to make tagatose – a sugar with about 60 percent fewer calories than table sugar – from glucose.
By using engineered bacteria, a team at Tufts University says the method could lower costs and widen food options.
The work was led by Professor Nikhil U. Nair. In his lab, researchers build microbes for use in food ingredients.
The study was focused on steering cell chemistry toward rare sugars that behave like table sugar in cooking.
Food companies want sweeteners that brown and add body, but many alternatives fall short on texture and taste.
Tagatose fits those demands, but its high price has limited its use outside niche products.
Why tagatose stays scarce
Natural sources contain only traces of tagatose, often less than 0.2 percent of the sugars present in foods.
Manufacturers usually make it by converting galactose, a sugar from lactose, with catalysts or enzymes that rearrange atoms.
“There are established processes to produce tagatose, but they are inefficient and expensive,” said Professor Nair.
Switching the raw material to cheap glucose could cut costs, but cells normally burn glucose for energy before making specialty sugars.
Redirecting bacterial pathways
Inside a modified strain of Escherichia coli, enzymes redirect glucose toward rare sugar building blocks instead of routine energy pathways.
The team used a whole-cell process, a method that keeps enzymes inside living microbes, so they avoided purifying proteins.
Genetic edits blocked key steps of glycolysis – the main route cells burn glucose for energy – and that rerouted carbon into rare-sugar pathways.
Because production happens inside bacteria, food manufacturers would still need downstream filtering to remove cells and leftover genetic material.
A slime mold enzyme
Researchers searched enzyme families and found a tool in the slime mold species Dictyostelium discoideum.
The protein acts as a phosphatase, an enzyme that removes phosphate groups, and it frees galactose by dephosphorylating galactose-1-phosphate.
“The key innovation in the biosynthesis of tagatose was in finding the slime mold Gal1P enzyme and splicing it into our production bacteria,” said Nair.
Computer simulations traced subtle hydrogen-bond patterns that help the enzyme ignore glucose, and that boundary keeps the reverse pathway on track.
Reversing cellular chemistry
To make galactose from glucose, the team reversed the Leloir pathway – a set of steps cells use to handle galactose.
The researchers blocked glycolysis early and stopped galactose from being re-phosphorylated, so newly made galactose stayed available for conversion.
Another enzyme called arabinose isomerase then rearranged galactose into tagatose, changing the sugar shape without adding or removing atoms.
Because galactose and tagatose sit near equilibrium in water, extra tuning must pull product away to raise final yields.
What the cultures produced
When the engineered bacteria grew on glucose, they made large amounts of galactose and smaller but measurable amounts of tagatose.
Increasing the activity of the slime mold enzyme raised output of both sugars, showing that this step limits how much tagatose can be produced.
A theoretical yield near 94.9 percent looks possible on paper because glucose does not lose half its carbon the way lactose does.
For now, the experiments read as proof of principle, since the same experimental trials still produced far more galactose than tagatose.
Keeping baking chemistry intact
Cooks need sweetness, but they also rely on sugar crystals to hold moisture and add body to batters.
Tagatose works as a bulk sweetener to add volume and texture, and it browns during heat-driven reactions.
Taste panels have put it close to sucrose, and the sugar reaches about 92 percent of sucrose sweetness in similar solutions.
Those traits could help reformulated foods feel familiar, yet product developers still must test stability, cost, and labeling.
A different trip through gut
After a person eats tagatose, the small intestine absorbs only part, and the rest moves on to the colon.
Gut microbes then do fermentation, breaking down sugar without oxygen, which limits rapid glucose spikes and changes what the body absorbs.
Clinical results show small changes in blood glucose and insulin after tagatose, matching its lower energy yield and slower uptake.
Because microbes produce gas and acids during fermentation, some people can feel bloated or get diarrhea when servings run high.
What labels can claim
Before a new sweetener spreads, regulators and companies look for safety data, predictable purity, and clear labeling.
The FDA notice lists D-tagatose for use in drinks, cereals, gum, candies, and baked goods.
That generally recognized as safe, meaning experts agree an ingredient is safe under intended use, does not cover every possible diet.
A separate rule allows a claim that D-tagatose does not promote dental caries, since mouth bacteria ferment it slowly.
Together, the enzyme discovery and pathway reversal show how living cells can make tagatose from glucose while keeping sugar-like cooking traits.
Next steps include raising tagatose output, tightening purification, and testing how it behaves in real recipes and long-term diets.
The study is published in the journal Cell Reports Physical Science.
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