Yeast production stimulates the manufacture of a low calorie sweetener derived from lactose

The quest to satisfy gourmands without adding waist has a new weapon in its arsenal: a yeast strain able to metabolize lactose, sugar in dairy products, tagatose, a natural sweetener containing less than half of calories from the table sugar. .

Yong-Su Jin, professor of food science and human nutrition at the University of Illinois, led the research team that developed the yeast strain, which produces tagatose in much larger quantities than traditional enzymatic manufacturing techniques. sugar or high fructose corn syrup.

The researchers published their work in the journal Nature Communications.

"Tagatose is a sweetener that has almost identical tastes and textures of sucrose, or table sugar, but tagatose contains far fewer calories than sucrose – about 40% sucrose," Jin said. "In addition, it does not increase blood sugar levels as much as sucrose or fructose." The glycemic index of tagatose is equal to 3, which is well below that of sucrose 68 and 24 fructose. as such, tagatosis is less risky for developing type 2 diabetes and other diseases caused by a rapid and repeated rise in blood sugar. "

Despite its benefits, tagatose has a high manufacturing cost that has prevented it from being widely used in commerce, Jin added. Although it is naturally present in fruits and dairy products, its concentrations are too low to effectively isolate tagatose. The traditional manufacturing process involves a multi-step enzymatic process that transforms galactose – a component of lactose – into tagatose.

Unfortunately, the enzyme reaction is so inefficient that only 30% of galactose is converted to tagatose, forcing manufacturers to use an expensive process to remove tagatose from the galactose mixture.

Jin's team used the internal machinery of yeast cells as tiny tagatose plants, much like ethanol manufacturers use yeast to produce fuel from corn. Researchers have developed a yeast strain producing tagatose from lactose by making two genetic modifications. First, they released a gene that allowed yeast to use galactose as a cellular fuel during lactose metabolism. Second, they added two genes that convert galactose into tagatose.

Thus, when yeast is fed lactose, its own metabolism leads to produce a solution containing 90% tagatose, much more than the 30% yield obtained by traditional manufacturing. Yeast reactors also operate at much larger scales than enzyme-based ones, which could enable efficient mass production of tagatose, Jin said.

"Another benefit is that our yeast-based process can use whey indirectly.Whey is an inevitable by-product of cheese making processes and Greek yogurt as a raw material," Jin said. "Due to the recent popularity of Greek yogurt, the disposal of whey is a problem in the dairy industry and we hope that our process can be used to solve the problem of excess whey. Yeast fermentation allows a report of the direct use of inexpensive dairy waste products, we expect that the cost of production of tagatose can be significantly reduced. "

The researchers will then explore the use of their yeast-based approach to make other products from lactose.

"We have shown that artificial yeast can efficiently and quickly use lactose.By further metabolic engineering, we can produce other valuable products from lactose abundant in whey, using our yeast strain artificial, "Jin said.