Characterization of a novel ß-galactosidase from Bifidobacterium adolescentis DSM 20083 active towards transgalactooligosaccharides

K.M.J. van Laere, T. Abee, H.A. Schols, G. Beldman, A.G.J. Voragen

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Abstract

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 -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 14, 16, 13, and 11 linked, signifying its role in the metabolism of galactooligosaccharides by B. adolescentis
Original languageEnglish
Pages (from-to)1379-1384
JournalApplied and Environmental Microbiology
Volume66
Publication statusPublished - 2000

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