Researchers at Tufts University have developed a biosynthetic method to produce tagatose, a naturally occurring but scarce sugar that offers sweetness comparable to sucrose whilst containing 60% fewer calories. The breakthrough, published in Cell Reports Physical Science, could provide a viable alternative to both conventional sugar and existing substitutes.

Tagatose exists in nature at extremely low concentrations, typically less than 0.2% of sugars in food sources. Whilst trace amounts appear in heated dairy products and certain fruits including apples and pineapples, the quantities are too negligible for extraction. Current manufacturing processes yield between 40-77% efficiency, making production costly and impractical for widespread use.

The Tufts team, led by associate professor Nik Nair, engineered Escherichia coli bacteria to function as biological production units. The modification involves introducing two key enzymes: galactose-1-phosphate-selective phosphatase (Gal1P) from slime mould and arabinose isomerase. The Gal1P enzyme reverses the typical metabolic pathway, converting abundant glucose into galactose rather than the reverse. The second enzyme then transforms galactose into tagatose.

This approach achieves yields reaching 95%, significantly surpassing conventional methods. The process uses glucose as feedstock rather than the more expensive galactose required in earlier attempts, improving economic feasibility.

At 92% the sweetness of sucrose, tagatose provides functional equivalence in applications. The US Food and Drug Administration has granted it "generally recognised as safe" status, placing it in the same regulatory category as salt and baking soda.

The sugar's metabolic pathway differs from conventional sugars. Only partial absorption occurs in the small intestine, with much of the substance fermented by gut bacteria in the colon. This characteristic results in minimal impact on blood glucose and insulin levels. Clinical studies demonstrate negligible plasma glucose or insulin increases following tagatose consumption, suggesting potential benefits for diabetic individuals.

Research indicates additional health effects. Rather than supporting cavity-causing oral bacteria as sucrose does, tagatose appears to inhibit their growth. Evidence suggests probiotic properties that support beneficial bacteria in both oral and gut environments.

The compound's physical properties enable its use as a bulk sweetener. Unlike high-intensity sweeteners that provide taste but no volume, tagatose replicates sugar's textural contribution in cooking and baking. It undergoes Maillard reactions during heating, producing browning comparable to table sugar. Taste testing studies position it closer to sucrose than other sugar substitutes.

Nair identifies the slime mould enzyme discovery as the critical innovation. By incorporating Gal1P into the bacterial system, the team redirected cellular metabolism to produce galactose from glucose—essentially running a natural pathway backwards. This technique could extend beyond tagatose to enable production of other rare sugars that occur naturally in insufficient quantities for conventional extraction.