Low-calorie sugar breakthrough: Bacteria turn glucose into D-tagatose with minimal blood sugar spike

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• Scientists modified E. coli to turn glucose into low-calorie sugar D-tagatose.
• D-tagatose: 92% as sweet as sugar, 1/3 the calories, low glycemic index
• This biological method could enable sustainable, large-scale tagatose production

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A team of scientists has reported a scientific advance that could change how sweetness is delivered in food, without the metabolic drawbacks tied to conventional sugar.

Writing in "Cell Reports Physical Science", the researchers outline a biological strategy for making D-tagatose, a naturally occurring sugar that has long attracted attention but has remained difficult to manufacture efficiently.

Unlike sucrose, D-tagatose delivers nearly the same sensory experience. It is about 92% as sweet as table sugar, yet provides only "one-third of the calories".

Even more significant is its "low glycemic index", meaning it avoids rapid surges in blood glucose. For people managing diabetes, and for companies working on low-calorie or "diabetes-friendly" products, these traits make it an appealing alternative.

Despite its promise, tagatose has struggled to move beyond niche use. In nature, it appears only in trace quantities. Industrially, it is typically derived from galactose, which itself is obtained from lactose in milk.

Because lactose splits evenly into glucose and galactose, half of the source material ends up unused. On top of that, chemical conversion routes depend on high heat, metal catalysts, and complicated purification, all of which raise costs and generate waste.

The new study takes a different path by shifting the work to living cells. Researchers genetically modified the bacterium Escherichia coli to transform glucose directly into tagatose. Glucose, already produced at massive scale for the food industry, is inexpensive and widely available.

To make this possible, the scientists rewired the microbe’s internal metabolism. They ran a natural sugar-processing pathway in reverse, prompting the cells to synthesize galactose from glucose rather than breaking it down.

A newly identified enzyme helped steer these reactions in the intended direction. Once galactose accumulated inside the cell, a second enzyme converted it into tagatose.

Because the entire sequence unfolds within the bacterium, the approach avoids purified enzymes and harsh chemical steps.

In laboratory trials, around 35% of the glucose was converted into galactose, yielding more than one gram per litre of tagatose. While far from industrial-scale output, the team describes this as a clear "proof of concept".

With further optimisation, the researchers believe this glucose-based, biological route could support sustainable, large-scale tagatose production. If that happens, it could open the door to sweeteners that satisfy the palate without carrying the same health burden, a timely prospect amid growing concerns over diabetes and obesity worldwide.