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Applied and Environmental Microbiology, July 2005, p. 3942-3950, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3942-3950.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Highly Hydrolytic Reuteransucrase from Probiotic Lactobacillus reuteri Strain ATCC 55730

S. Kralj,^1,4 E. Stripling,^1,4 P. Sanders,² G. H. van Geel-Schutten,^1,3 and L. Dijkhuizen^1,4*

Centre for Carbohydrate Bioengineering, TNO-University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands,¹ Innovative Ingredients and Products, TNO Nutrition and Food Research, Rouaanstraat 27, 9723 CC Groningen, The Netherlands,² Innovative Ingredients and Products, TNO Nutrition and Food Research, Utrechtseweg 48, 3704 HE Zeist, The Netherlands,³ Department of Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands⁴

Received 28 December 2004/ Accepted 13 February 2005

Lactobacillus reuteri strain ATCC 55730 (LB BIO) was isolated as a pure culture from a Reuteri tablet purchased from the BioGaia company. This probiotic strain produces a soluble glucan (reuteran), in which the majority of the linkages are of the -(14) glucosidic type (70%). This reuteran also contains -(16)- linked glucosyl units and 4,6-disubstituted -glucosyl units at the branching points. The LB BIO glucansucrase gene (gtfO) was cloned and expressed in Escherichia coli, and the GTFO enzyme was purified. The recombinant GTFO enzyme and the LB BIO culture supernatants synthesized identical glucan polymers with respect to linkage type and size distribution. GTFO thus is a reuteransucrase, responsible for synthesis of this reuteran polymer in LB BIO. The preference of GTFO for synthesizing -(14) linkages is also evident from the oligosaccharides produced from sucrose with different acceptor substrates, e.g., isopanose from isomaltose. GTFO has a relatively high hydrolysis/transferase activity ratio. Complete conversion of 100 mM sucrose by GTFO nevertheless yielded large amounts of reuteran, although more than 50% of sucrose was converted into glucose. This is only the second example of the isolation and characterization of a reuteransucrase and its reuteran product, both found in different L. reuteri strains. GTFO synthesizes a reuteran with the highest amount of -(14) linkages reported to date.

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* Corresponding author. Mailing address: Department of Microbiology, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands. Phone: 31.50.3632150. Fax: 31.50.3632154. E-mail: l.dijkhuizen{at}rug.nl.

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Applied and Environmental Microbiology, July 2005, p. 3942-3950, Vol. 71, No. 7
0099-2240/05/$08.00+0     doi:10.1128/AEM.71.7.3942-3950.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

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