Structural characterization of glucosylated GOS derivatives synthesized by the Lactobacillus reuteri GtfA and Gtf180 glucansucrase enzymes

Hient.T Pham,Lubbert Dijkhuizen,Sander S Van Leeuwen

doi:10.1016/j.carres.2018.10.003

Hient.T Pham, Lubbert Dijkhuizen + Show 1 more

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https://doi.org/10.1016/j.carres.2018.10.003

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Journal: Carbohydrate research	Publication Date: Oct 22, 2018
Citations: 6	License type: cc-by

Affiliation: University of Groningen

Abstract

β-Galacto-oligosaccharides (GOS) are used commercially in infant nutrition, aiming to functionally replace human milk oligosaccharides (hMOS). Glucansucrases Gtf180-ΔN and GtfA-ΔN of Lactobacillus reuteri strains convert sucrose into α-glucans with (α1→6)/(α1→3) and (α1→4)/(α1→6) glucosidic linkages, respectively. Previously we reported that both glucansucrases glucosylate lactose, producing a minimum of 5 compounds (degree of polymerization 3–4) (GL34 mixture) with (α1→2/3/4) linkages. This GL34 mixture exhibited growth stimulatory effects on various probiotic bacteria. Aiming to obtain additional compounds mimicking hMOS in structure and function, we here studied glucosylation of 3 commercially available galactosyl-lactose GOS compounds. Both Gtf180-ΔN and GtfA-ΔN were unable to use 3′-galactosyl-lactose (β3′-GL), but used sucrose to add a single glucose moiety to 4′-galactosyl-lactose (β4′-GL) and 6′-galactosyl-lactose (β6′-GL). β6′-GL was elongated at its reducing glucosyl unit with an (α1→2)-linked moiety and at its non-reducing end with an (α1→4) linked moiety; β4′-GL was only elongated at its reducing end with an (α1→2) linked moiety. Glucansucrases Gtf180-ΔN and GtfA-ΔN thus can be used to produce galactosyl-lactose-derived oligosaccharides containing (α1→2) and (α→4) glucosidic linkages, potentially with valuable bioactive (prebiotic) properties.

Highlights

The beneficial effects on human and animal health of so called prebiotics, a class of bioactive oligosaccharides, are widely studied [1,2,3,4]
A prebiotic is defined as “a substrate that is selectively utilized by host microorganisms conferring a health benefit” [5]
Novel non-digestible carbohydrates and prebiotic compounds are still high in demand for food and feed product applications [9]

Summary

Introduction

The beneficial effects on human and animal health of so called prebiotics, a class of bioactive oligosaccharides, are widely studied [1,2,3,4]. The dominant members are GOS, with (β1→2), (β1→3), (β1→4), or (β1→6) linked galactosyl moieties, of various sizes (mostly DP2 - DP5). These prebiotic compounds stimulate growth of probiotic bacteria to various extents [7,10,11]. Lactosucrose and lactulose are well studied for their selective stimulatory effects on human gut bacteria [12,13]

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