Jun 25, 2019 | Updated: 07:39 AM EDT

Yeast-based Approach in Manufacturing Low-Calorie Sugar Tagatose

Apr 16, 2019 10:08 AM EDT

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There is good news for people who love sweets but are weight conscious.

A team of researchers from the University of Illinois developed a yeast strain that controls lactose metabolism into tagatose. Lactose is a disaccharide sugar found in milk while tagatose is less than 50 percent calories of table sugar. 

Professor of food science and human nutrition Yong-Su Jin, main author of the work published in the journal Nature Communications, developed the yeast strain that produces larger quantities of tagatose than through conventional enzymatic manufacturing techniques. This allows a cheaper option to sugar.  

"Tagatose is a sweetener that exhibits almost identical tastes and textures of sucrose, or table sugar. However, tagatose has many fewer calories than sucrose -- about 40% of sucrose," Jin said. "In addition, it does not increase blood glucose levels as much as sucrose or fructose. The glycemic index of tagatose is 3, which is much lower than that of sucrose, 68, and fructose, 24. As such, tagatose carries a lower risk for developing Type 2 diabetes and other diseases caused by rapid and repeating glucose increases in blood."

There are many hindrances when it comes to producing tagatose. It incurs a high cost of manufacture when produced. Despite being an active ingredient in fruits and dairy products, it is not effective to isolate tagatose as the result would be too low concentrations. Companies produce tagatose through a multi-step enzymatic process that converts galactose into tagatose. 

The inefficiency of the enzyme reaction results to only 30 percent of galactose being converted into tagatose.

The removal of tagatose from the galactose mixture require an expensive process for manufacturers to use. 
According to Science Daily, "Jin's team used the internal machinery of yeast cells as tiny tagatose factories, much like how ethanol manufacturers use yeast to produce fuel from corn. The researchers engineered a strain of yeast that produces tagatose from lactose by making two genetic tweaks. First, they took out a gene that let the yeast use galactose as cellular fuel during lactose metabolism. Second, they added two genes that convert galactose into tagatose."

The metabolism of the lactose-fed yeast increases the production of a solution that is 90 percent tagatose. The probability of an efficient mass production of tagatose increases when yeast reactors are used compared to enzyme-based ones. 

"Another advantage is that our yeast-based process can use whey indirectly. Whey is an inevitable byproduct of the cheese and Greek yogurt manufacturing processes as a raw material," Jin said. "Due to the recent popularity of Greek yogurt, the disposal of whey is an issue in the dairy industry. We hope our process can be used to resolve the surplus whey problem. As our yeast fermentation-based approach allows a higher product ratio and the direct use of inexpensive dairy waste, we expect that the production cost of tagatose can be significantly reduced."

The team will research further their method based on yeast to produce other lactose products.

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