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Applied and Environmental Microbiology, April 2000, p. 1379-1384, Vol. 66, No. 4
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Characterization of a Novel beta -Galactosidase from Bifidobacterium adolescentis DSM 20083 Active towards Transgalactooligosaccharides

Katrien M. J. Van Laere,1 Tjakko Abee,2 Henk A. Schols,1 Gerrit Beldman,1 and Alphons G. J. Voragen1,*

Laboratories for Food Chemistry1 and Food Microbiology,2 Department of Food Technology and Nutritional Sciences, Wageningen University, Wageningen, The Netherlands

Received 19 July 1999/Accepted 19 January 2000

This paper reports on the effects of both reducing and nonreducing transgalactooligosaccharides (TOS) comprising 2 to 8 residues on the growth of Bifidobacterium adolescentis DSM 20083 and on the production of a novel beta -galactosidase (beta -Gal II). In cells grown on TOS, in addition to the lactose-degrading beta -Gal (beta -Gal I), another beta -Gal (beta -Gal II) was detected and it showed activity towards TOS but not towards lactose. beta -Gal II activity was at least 20-fold higher when cells were grown on TOS than when cells were grown on galactose, glucose, and lactose. Subsequently, the enzyme was purified from the cell extract of TOS-grown B. adolescentis by anion-exchange chromatography, adsorption chromatography, and size-exclusion chromatography. beta -Gal II has apparent molecular masses of 350 and 89 kDa as judged by size-exclusion chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, indicating that the enzyme is active in vivo as a tetramer. beta -Gal II had an optimal activity at pH 6 and was not active below pH 5. Its optimum temperature was 35°C. The enzyme showed highest Vmax values towards galactooligosaccharides with a low degree of polymerization. This result is in agreement with the observation that during fermentation of TOS, the di- and trisaccharides were fermented first. beta -Gal II was active towards beta -galactosyl residues that were 1right-arrow4, 1right-arrow6, 1right-arrow3, and 1left-right-arrow 1 linked, signifying its role in the metabolism of galactooligosaccharides by B. adolescentis.

* Corresponding author. Mailing address: Laboratory for Food Chemistry, Department of Food Technology and Nutritional Sciences, Wageningen University, Bomenweg 2, 6703 HD Wageningen, The Netherlands. Phone: 31-317-484811. Fax: 31-317-484893. E-mail: Fons.Voragen{at}Chem.Fdsci.Wau.NL.

Applied and Environmental Microbiology, April 2000, p. 1379-1384, Vol. 66, No. 4
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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