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Galactose-tagatose conversion for sweetening of fermented dairy products


Key words Dairy, fermented, milk, galactose, tagatose, sweetener, arabinose isomerase, sugar substitute
Latest version 2013/09/05
Completed by INRA - IATE

How does it work?

Primary objective To produce a cheap, healthy and low-calorie sweetener for fermented dairy products
Working principle In dairy products, D-galactose is produced by lactic acid fermentation.

D-galactose can be efficiently converted into D-tagatose, a functional sweetener, thanks to a thermostable enzyme: L-arabinose isomerase.(1) L-arabinose isomerase can be used as such into the milk OR using L-arabinose isomerase producing bacteria, which must be allowed for food consumption (e.g. Lactobacillus, Bacillus, Streptococcus, Thermus, Thermotoga, Geobacillus, Alicylobacillus, etc.). (2) The bacteria can naturally express the enzyme or it can be transformed with a vector in order to express it (3)(4)(5)(6). Either the enzyme or the enzyme-producing bacteria can be added directly into the milk and left in, or contacted with the milk and then be recovered. (2)

Additional effects D-tagatose is a natural ketohexose as sweet as table sugar (sucrose), but three times less caloric (1.5kcal/g vs. 4kcal/g for the sucrose). Clinical controversies and organoleptic problems associated with the use of non-carbohydrate sweeteners make D-tagatose one of the best dietetic alternatives to sugar. (7)

The enzymatic conversion can occur at pH and temperature conditions that are suitable with lactic acid fermentation, enabling the manufacturer to carry out both operations at the same time. (2)

Important process parameters pH, temperature, l-arabinose isomerase concentration
Important product parameters D-galactose content

What can it be used for?

Products Fermented dairy products, including: yoghurt, cultured buttermilk, Acidophilus milk, sour cream, kefir, koumiss, labneh, etc. (2)
Operations sweetening
Solutions for short comings production of low-caloric dairy products

What can it NOT be used for?

Products Non-dairy products

Non-fermented products

Operations Any other operation than sugar conversion (sweetening)
Other limitations See consumer aspects
Risks or hazards not known


Maturity Currently the technology is available for direct commercial application, through patent licencing by INRA Transfert, but has not been industrially implemented yet.

Additionally, research is still ongoing i) to extend the range of L-arabinose isomerases available by using microorganisms other than B. stearothermophilus, and ii) to optimize their enzymatic activity (thermostability, optimal temperature and pH, etc.). Further developments are expected for the methods of enzymatic conversion or bioconversion of galactose into tagatose directly in dairy products, or even the production of the tagatose ingredient.

Modularity /Implementation This method can be carried out in the same equipment as for the lactic acid fermentation.

The conversion can be carried out continuously, with the immobilised enzyme in a packed-bed reactor. (8)

Consumer aspects Consumers are interested in low-calorie, natural products.

The “GMO” aspect (for transformed bacteria) can be reluctant for some consumers if they are aware of it.

Legal aspects The technology is internationally patented (2).

Licenses are available through Inra Transfert for commercial applications in the dairy industry.

Environmental aspects not known

Further Information

Institutes INRA - MICA, Center of Biotechnology of Sfax
Companies INRA Transfert
  1. Lee S. et al 2008. Thermostable and acidophilic arabinose isomerase and procès for preparing tagatose thereby. KPOP.
  2. Rhimi M., Chouayekh H., Maguin E., Bejar S. 2009. L-arabinose isomerase for converting D-galactose into D-tagatose in a dairy product which contains D-galactose. WO2009066127, EP2211643, TN2010/0226.
  3. Byoung-Chan K. et al 2002. Cloning, expression and charaterization of L-arabinose isomérase from Thermotoga neapolitana: Bioconversion of D-galactose using the enzyme. FEMS Microbiology Letters, 212: 121-126.
  4. Hyo-Jung O., Hye-Jung K. and Deok-Kun O. 2006. Increase in D-tagatose production rate by site-directed mutagenesis of L-arabinose isomérase from Geobacillus thermodenitrificans. Biotechnology Letters, 28: 145-149.
  5. Jung-Woo K. et al 2003. Production of tagatose by a recombinant thermotable L-arabinose isomérase from Thermus sp. IM6501. Biotechnology Letters, 25: 963-967.
  6. Jorgensen F. et al 2004. Enzymatic conversion of D-galactose to D-tagatose: heterologous expression o-and characterisation of a thermostable L-arabinose isomérase from Thermoanaerobacter mathranii. Applied microbiology and biotechnology, 64: 816-822.
  7. Deok-Kun O. 2007. Tagatose: properties, applications, and biotechnological processes. Applied microbiology and biotechnology, 76: 1-8.
  8. Ryu S.A. et al 2003. Continuous D-tagatose production by immobilized thermostable L-arabinose isomérase in a packed-bed bioreactor. Biotechnology progress, 19: 1643-1647.

pH, temperature, l-arabinose isomerase concentration D-galactose content Fermentors 2.1.3 chemical, biological conversion biotechnology INRA Transfert database of technological offers; contact WikiSysop :Template:Review document :Template:Review status

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Created by Hte inra on 30 May 2013, at 12:32