Analysis of Structural and Functional Differences of Glucans Produced by the Natively Released Dextransucrase of Liquori
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Analysis of Structural and Functional Differences of Glucans Produced by the Natively Released Dextransucrase of Liquorilactobacillus hordei TMW 1.1822 Jonas Schmid 1 & Daniel Wefers 2,3 & Rudi F. Vogel 1 & Frank Jakob 1 Received: 28 April 2020 / Accepted: 12 August 2020/ # The Author(s) 2020
Abstract
The properties of the glucopolymer dextran are versatile and linked to its molecular size, structure, branching, and secondary structure. However, suited strategies to control and exploit the variable structures of dextrans are scarce. The aim of this study was to delineate structural and functional differences of dextrans, which were produced in buffers at different conditions using the native dextransucrase released by Liquorilactobacillus (L.) hordei TMW 1.1822. Rheological measurements revealed that dextran produced at pH 4.0 (MW = 1.1 * 108 Da) exhibited the properties of a viscoelastic fluid up to concentrations of 10% (w/v). By contrast, dextran produced at pH 5.5 (MW = 1.86 * 108 Da) was gel-forming already at 7.5% (w/v). As both dextrans exhibited comparable molecular structures, the molecular weight primarily influenced their rheological properties. The addition of maltose to the production assays caused the formation of the trisaccharide panose instead of dextran. Moreover, pre-cultures of L. hordei TMW 1.1822 grown without sucrose were substantial for recovery of higher dextran yields, since the cells stored the constitutively expressed dextransucrase intracellularly, until sucrose became available. These findings can be exploited for the controlled recovery of functionally diverse dextrans and oligosaccharides by the use of one dextransucrase type. Keywords Lactic acid bacteria . Dextransucrase . Dextran . Molecular weight . Rheology . Panose
* Frank Jakob [email protected]
1
Chair of Technical Microbiology, Technical University of Munich (TUM), Freising, Germany
2
Division of Food Chemistry, Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Halle (Saale), Germany
3
Department of Food Chemistry and Phytochemistry, Karlsruhe Institute of Technology, Karlsruhe, Germany
Applied Biochemistry and Biotechnology
Introduction The utilization of microbial exopolysaccharides (EPSs) is of growing importance and commercial interest due to their great structural diversity and concomitant manifold properties. They can be used instead of synthetically produced additives in cosmetics and food products and may replace commonly used emulsifiers because of their water-binding capacity or rather hydrocolloid properties [1–5]. Furthermore, EPSs may play a future role in applications like tissue engineering, drug delivery systems, and other medical applications [6–10] or even fields like biofuel research [11], as they are usually involved in the formation of biofilms [12–19]. One of the most prominent EPSs is dextran, which is commercially exploited in fermented foods like sourdoughs, panettone, or fruit juices, and applied as blood plasma volume expander or as stationary phase of size-exclusion c
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