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TOKSOY ÖNER, EBRU

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TOKSOY ÖNER

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2015 - 20182
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Has files: true × Subject: Halomonas smyrnensis ×

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    PublicationOpen Access
    Levansucrase from Halomonas smyrnensis AAD6(T): first halophilic GH-J clan enzyme recombinantly expressed, purified, and characterized
    (SPRINGER, 2018-11) TOKSOY ÖNER, EBRU; Kirtel, Onur; Menendez, Carmen; Versluys, Maxime; Van den Ende, Wim; Hernandez, Lazaro; Oner, Ebru Toksoy
    Fructans, homopolymers of fructose produced by fructosyltransferases (FTs), are emerging as intriguing components in halophiles since they are thought to be associated with osmotic stress tolerance and overall fitness of microorganisms and plants under high-salinity conditions. Here, we report on the full characterization of the first halophilic FT, a levansucrase from Halomonas smyrnensis AAD6(T) (HsLsc; EC 2.4.1.10). The encoding gene (lsc) was cloned into a vector with a 6xHis Tag at its C-terminus, then expressed in Escherichia coli. The purified recombinant enzyme (47.3kDa) produces levan and a wide variety of fructooligosaccharides from sucrose, but only in the presence of high salt concentrations (>1.5M NaCl). HsLsc showed Hill kinetics and pH and temperature optima of 5.9 and 37 degrees C, respectively. Interestingly, HsLsc was still very active at salt concentrations close to saturation (4.5M NaCl) and was selectively inhibited by divalent cations. The enzyme showed high potential in producing novel saccharides derived from raffinose as both fructosyl donor and acceptor and cellobiose, lactose, galactose, and -arabinose as fructosyl acceptors. With its unique biochemical characteristics, HsLsc is an important enzyme for future research and potential industrial applications in a world faced with drought and diminishing freshwater supplies.
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    PublicationOpen Access
    Genomic analysis reveals the biotechnological and industrial potential of levan producing halophilic extremophile, Halomonas smyrnensis AAD6T
    (SPRINGER INTERNATIONAL PUBLISHING AG, 2015-12) TOKSOY ÖNER, EBRU; Diken, Elif; Ozer, Tugba; Arikan, Muzaffer; Emrence, Zeliha; Oner, Ebru Toksoy; Ustek, Duran; Arga, Kazim Yalcin
    Halomonas smyrnensis AAD6T is a gram negative, aerobic, and moderately halophilic bacterium, and is known to produce high levels of levan with many potential uses in foods, feeds, cosmetics, pharmaceutical and chemical industries due to its outstanding properties. Here, the whole-genome analysis was performed to gain more insight about the biological mechanisms, and the whole-genome organization of the bacterium. Industrially crucial genes, including the levansucrase, were detected and the genome-scale metabolic model of H. smyrnensis AAD6T was reconstructed. The bacterium was found to have many potential applications in biotechnology not only being a levan producer, but also because of its capacity to produce Pel exopolysaccharide, polyhydroxyalkanoates, and osmoprotectants. The genomic information presented here will not only provide additional information to enhance our understanding of the genetic and metabolic network of halophilic bacteria, but also accelerate the research on systematical design of engineering strategies for biotechnology applications.