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    Characterization and immune-modulatory roles of branched glucan and acetylated gluco-oligosaccharides produced by glucansucrase 40 from Leuconostoc mesenteroides YTU 40
    (Nature Portfolio, 2025) Dere, Sevda; Ispirli, Humeyra; Korkmaz, Kader; Tuncil, Yunus Emre; Sagdic, Osman; Narbad, Arjan; Dertli, Enes
    Glucansucrases (GS) are functional enzymes for the production of distinct glucan and gluco-oligosaccharide structures with potential bioactive characteristics. In this study, an active glucansucrase (GS40) was identified within the genome of Leuconostoc mesenteroides YTU 40 that was further cloned, heterologously expressed and biochemically characterised. GS40 was capable of production of a branched dextran with similar to 20% (1 -> 3)-alpha-D-Glc residues detected by(1)H and(13)C NMR analysis. Acceptor reactions of GS40 with maltose and cellobiose were performed and distinct maltose/cellobiose derivative acetylated gluco-oligosaccharides were produced detected by TLC, NMR and LC-MS analysis. The bioactive characteristics of branched dextran and gluco-oligosaccharides were tested by determination of their immune-modulatory roles in terms of triggering IL-12, IL-10, IL-4 and TNF-alpha cytokine levels. These findings can be important to unveil the role of glucansucrases for the production of gluco-oligosaccharides that can be used as functional ingredients for food and other industries.
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    Physicochemical characterization of glucan AK7 produced by quinoa sourdough isolate Leuconostoc mesenteroides AK7
    (Elsevier, 2025) Ispirli, Humeyra; Arslan, Seyma; Tuncer, Fatma; Kasapoglu, Muhammed Z.; Ortakci, Fatih; Tuncil, Yunus Emre; Dertli, Enes
    The production of exopolysaccharides (EPS) by Lactic Acid Bacteria (LAB) is technologically crucial because it has a wide range of applications in food technology, biotechnology, and health. In the present work, a new quinoa sourdough isolate of Leuconostoc mesenteroides strain AK7 was identified as a novel producer of a dextran-type EPS. The monomeric units of EPS AK7 were confirmed by HPLC analysis, while NMR spectroscopy and GC-MS linkage analysis further verified the EPS structure as a branched dextran containing mainly (1-6)-linked alpha- D-glucose units with (1-3,6)-linked alpha- D-glucose unit as branching points. An average molecular weight of 1.2 x 106 Da was detected for glucan AK7. FTIR analysis was applied to determine the functional units of dextran AK7. In terms of thermal features, TGA and DSC analysis were applied and a specific degradation temperature of 300 degrees C was found for dextran AK7. The morphology of the lyophilized EPS displayed a rough, dense, and porous structure, as observed through SEM analysis. Dextran AK7 revealed a semi-crystalline nature detected by XRD analysis. These structural and functional properties of dextran AK7 produced by Leuconostoc mesenteroides AK7 from quinoa sourdough suggest its potential usage for food industry applications.
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    Utilisation of an active branching sucrase from Lactobacillus kunkeei AP-37 to produce techno-functional poly-oligosaccharides
    (Elsevier, 2023) Ispirli, Huemeyra; Korkmaz, Kader; Arioglu-Tuncil, Seda; Bozkurt, Fatih; Sagdic, Osman; Tuncil, Yunus Emre; Narbad, Arjan
    Glucansucrase AP-37 was extracted from the culture supernatant of Lactobacillus kunkeei AP-37 and character-istics of the glucan produced by the active glucansucrase in terms of structural and functional roles were determined in this study. A molecular weight around 300 kDa was observed for glucansucrase AP-37 and its acceptor reactions with maltose, melibiose and mannose were also conducted to unveil the prebiotic potential of the poly-oligosaccharides formed via these reactions. The core structure of glucan AP-37 was determined by 1H and 13C NMR and GC/MS analysis which revealed that glucan AP-37 was a highly branched dextran composing of high levels of (1-+ 3)-linked alpha-D-glucose units with low levels of (1-+ 2)-linked alpha-D-glucose units. The structural features of the glucan formed, demonstrated that glucansucrase AP-37 was an alpha-(1-+ 3) branching sucrase. Dextran AP-37 was further characterised by FTIR analysis and XRD analysis demonstrated its amorphous nature. A fibrous compact morphology was observed for dextran AP-37 with SEM analysis whereas TGA and DSC analysis revealed its high stability as no degradation was observed up to 312 degrees C. Finally, the prebiotic potential of the dextran AP-37 and the gluco-oligosaccharides produced with the acceptor reaction of alpha-(1-+ 3) branching sucrase AP-37 were determined and promising results were found for the gluco-oligosaccharides to act as prebiotics.