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Applied and Environmental Microbiology, April 2000, p. 1379-1384, Vol. 66, No. 4
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
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of a Novel
-Galactosidase from
Bifidobacterium adolescentis DSM 20083 Active towards
Transgalactooligosaccharides
-galactosidase (
-Gal II). In cells grown on
TOS, in addition to the lactose-degrading
-Gal (
-Gal I), another
-Gal (
-Gal II) was detected and it showed activity towards TOS
but not towards lactose.
-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.
-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.
-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.
-Gal II was active towards
-galactosyl residues that were 1
4, 1
6, 1
3, and 1
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.
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