Scientists develop low-calorie sugar alternative using engineered bacteria

New biological method enables cleaner production of D-tagatose, a sugar with fewer calories and minimal impact on blood sugar levels.

In a scientific breakthrough that could significantly influence the future of sweeteners, researchers have developed a new biological method to produce D-tagatose, a rare sugar that closely mimics the taste of regular sugar while offering major health advantages. The findings were published in the journal Cell Reports Physical Science.

D-tagatose is known to be about 92% as sweet as table sugar, yet it contains only one-third of the calories. More importantly, it has a low glycaemic index, meaning it does not cause sharp rises in blood glucose levels. Because of this, tagatose is considered a promising option for people with diabetes and for food companies working on low-calorie or diabetes-friendly products.

Until now, large-scale production of tagatose has been a major hurdle. The sugar exists only in very small quantities in nature. Conventional manufacturing methods depend on galactose, which is usually extracted from lactose found in milk. Since lactose contains equal parts glucose and galactose, half of the raw material goes unused. These chemical processes are also expensive, inefficient, and generate chemical waste due to high temperatures, metal catalysts, and complex purification steps.

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The new study offers a cleaner alternative by using genetically engineered Escherichia coli (E. coli) bacteria. Researchers modified the bacteria to convert glucose directly into tagatose. Glucose is inexpensive, widely available, and already used on a large scale in the food industry.

To achieve this, scientists reprogrammed the bacteria’s internal metabolic pathways. They reversed a natural sugar-breaking process so that the cells began producing galactose from glucose. A newly identified enzyme helped drive this reaction in the required direction. Once galactose was formed inside the cell, another enzyme converted it into tagatose.

The entire process occurs inside living cells, removing the need for purified enzymes or harsh chemicals. In laboratory tests, the engineered bacteria converted around 35% of glucose into galactose and produced more than one gram per litre of tagatose.

Although these production levels are not yet suitable for commercial use, researchers say the results provide strong proof of concept. With further optimisation, this approach could allow sustainable, large-scale production of tagatose using only glucose, opening new possibilities for healthier sugar alternatives.