- 건국대학교

	KU Research Team Develops Low Calorie Sweetner ‘Tagatose’ Production Enzyme
	관리자		349		2020.10.08

A research team led by Professor Deokkun Oh from Department of Integrative Bioscience and Biotechnology at Konkuk Institute of Science and Technology(KIT) announced on the 5th that they have succeeded in developing an enzyme that can produce tagatose, a low calorie functional sweetner, from fructose. The research was conducted with the support of Ministry of Science and Technology’s basic research project and it will be published in Volume 10, No.19, 2020 (IF=12.350), an authoritative international journal in chemical engineering. (Thesis title: Development of Tagaturonate 3-Epimerase into Tagatose 4-Epimerase with a Biocatalytic Route from Fructose to Tagatose) (Co-first authors: Academic Reserach Professor Kyungchul Shin, Doctoral Graduate student Taeeui Lee, Professor Deokkun Oh)
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Tagatose, which is a natural sweetener present in dairy products in small quantities, has a very low blood Glycemic Index(GI) despite its similar sweetness to sugar, and is a low calorie sweetener approved by FDA. Tagatose is given attention for its beneficial biological effects such as anti-drug, anti-obesity, antioxidant, and tooth decay prevention, but current manufacturing methods based on galactose derived from lactose have a limitation in popularizing them due to high manufacturing cost. The previous tagatose had been produced mainly from galactose by L-arabinose isomerase. Galactose, which does not exist alone in nature but in the form of lactose combined with glucose, has a limitation for unstable supply and high price of lactose. Thus, fructose with stable supply and low price has been proposed as an ideal substitute for lactose, yet no enzyme has been found to produce tagatose from fructose.
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The research team examined the production of tagatose in fructose using many glycoprotein enzymes and discovered that the only enzyme, Tagaturonate 3-epimerase(Figure 2), could produce tagatose in trace amounts from fructose. Since this enzyme has a limitation of low conversion activation for the production of tagatose, the team conducted a research to improve the enzyme to increase the conversion activation. The research team found amino acids that greatly affect fructose-tagatose conversion activation through rational design technique and analysis of amino acid interaction in the enzyme-active area. The team has also developed a new enzyme, tagatose 4-epimerase, with the application of directed evolution technology, error-p rone PCR, DNA shuffling, and saturation mutations(Figure 3). Fructose-tagatose conversion activation of the enzyme has improved 184 times, however, fracturonate-tagatronate conversion activation has decreased 52 times with the change of five amino acid residue(Figure 4). Finally, the team has successfully produced 213 g/L of tagatose, the level of industrial application, by making two-hour reaction of tagatose 4-epimerization and fructose.
Professor Oh said, “By discovering tagaturonate 3-epimerase that produces trace amounts of tagatose and dramatically increasing enzyme activity with protein engineering technology, we have created a new enzyme that produces tagatose from fructose,” adding that “As an ideal production path for tagatose is prepared to replace the original method of using lactose, we can expect more economical tagatose production.”
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