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Bioresour Technol. 2011 Feb;102(3):3309-15. doi: 10.1016/j.biortech.2010.10.078. Epub 2010 Oct 23.

Production of D-tagatose, a low caloric sweetener during milk fermentation using L-arabinose isomerase.

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Laboratoire d'Enzymes et de Métabolites des Procaryotes, Centre de Biotechnologie de Sfax, Sfax, Tunisia.


Lactobacillusdelbrueckii subsp. bulgaricus and Streptococcus thermophilus are used for the biotransformation of milk in yoghurt. During milk fermentation, these lactic acid bacteria (LAB) hydrolyze lactose producing a glucose moiety that is further metabolized and a galactose moiety that they are enable to metabolize. We investigated the ability of L. bulgaricus and S. thermophilus strains expressing a heterologous L-arabinose isomerase to convert residual D-galactose to D-tagatose. The Bacillus stearothermophilus US100l-arabinose isomerase (US100l-AI) was expressed in both LAB, using a new shuttle vector where the araA US100 gene is under the control of the strong and constitutive promoter of the L. bulgaricus ATCC 11842 hlbA gene. The production of L-AI by these LAB allowed the bioconversion of D-galactose to D-tagatose during fermentation in laboratory media and milk. We also established that the addition of L-AI to milk also allowed the conversion of D-galactose into D-tagatose during the fermentation process.

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