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    Bifidogenic property of enzymatically synthesized water-insoluble ?-glucans with different ?-1,6 branching ratio
    (Elsevier Sci Ltd, 2022) Ryu, Hye-Jung; Jung, Dong-Hyun; Yoo, Sang-Ho; Tuncil, Yunus E.; Lee, Byung-Hoo
    Bifidobacteria uses insoluble resistant starch (RS) fractions as prebiotics in the colon, consequently improving human intestinal health. In this study, various alpha-1,6 linkage ratios of insoluble alpha-glucans were synthesized by amylosucrase from Neisseria polysaccharea and glycogen branching enzyme from Rhodothermus obamensis to investigate the effect of branching patterns on Bifidogenic property. Different ratios (0%-4%) of alpha-1,6 branched insoluble alpha-glucans with alpha-1,4 linked backbones were effectively synthesized. Additionally, the proportions of RS fraction in the synthesized alpha-glucans were 69.5%-81.9% after the cooking process, which are higher amounts than amylomaize VII (36.8%). As various Bifidobacteria used the insoluble branched alpha-glucans, the structure with 2.5% of 1,6 linkage showed the highest consumption yield, more than 70%, among all tested strains. Therefore, the insoluble alpha-glucans with different alpha-1,6 linkage ratios can be applied as prebiotic ingredients to modulate the Bifidobacterium species to enhance colon health and related outcomes.
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    Corn arabinoxylan has a repeating structure of subunits of high branch complexity with slow gut microbiota fermentation
    (Elsevier Sci Ltd, 2022) Xu, Haidi; Reuhs, Bradley L.; Cantu-Jungles, Thaisa M.; Tuncil, Yunus E.; Kaur, Amandeep; Terekhov, Anton; Martens, Eric C.
    Corn arabinoxylan (CAX), a cell wall-derived dietary fiber, was extracted with alkali, partially purified, and treated with hydrolytic enzymes in order to investigate the relationship of fine structure and fermentability by the human gut microbiota. Glycosyl composition and linkage analysis of CAX and two hydrolysates, coupled with molecular size analysis, indicated an organized structural feature of the native polymer, which consists of a repeating structural subunit containing complex branching patterns along the xylan backbone and flanked by regions of less complexity. The two lengths of the highly branched subunit were isolated and were shown to have enhanced slow fermentation property compared to the native structure (3.3 vs. 5.9 mL gas, 4 h), that was related to increasing complexity of the branched structures. Lower molecular size structures with higher branch complexity fermented slower, contrary to a conventional view that small fiber structures approaching the oligosaccharide level are necessarily more rapidly fermented.
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    Dietary Fibers of Tree Nuts Differ in Composition and Distinctly Impact the Fecal Microbiota and Metabolic Outcomes In Vitro
    (Amer Chemical Soc, 2023) Sahin, Merve; Arioglu-Tuncil, Seda; Unver, Ahmet; Deemer, Dane; Lindemann, Stephen R.; Tuncil, Yunus E.
    This study aimed to evaluate and compare the effectsof dietaryfibers (DFs) of commercially important tree nuts (almond, cashew,hazelnut, pistachio, and walnut) on gut microbiota in vitro. Microbial compositions and short-chain fatty acids were determinedusing 16S rRNA sequencing and gas chromatography (GC), respectively.Neutral and acidic monosaccharides were analyzed using GC/MS and spectrophotometry,respectively. Our results revealed that cashew fibers exhibit higherbutyrate formation compared to others. Accordingly, cashew fiber promotedbutyric acid-producing bacteria-related operational taxonomic units(OTUs; Butyricimonas and Collinsella) at higher relative abundances. The higher butyrogenic capacityof cashew fiber is mainly attributed to its higher soluble/total DFratio and remarkably distinct monosaccharide composition. Additionally,nut fibers stimulated family Lachnospiraceae- and Ruminococcaceae-related OTUs. These findings show that althoughthe degree of promotion is nut type-dependent, nut fibers are generallycapable of promoting beneficial microbes in the colon, further suggestingthat DFs of tree nuts are contributing factors to their health-promotingeffects.
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    Hazelnut (Corylus avellana L.) skin, a by-product of hazelnut industry, possesses oil with high oxidative and thermal stabilities
    (Wiley, 2023) Celik, Omer F.; Aktas, Nesimi; Tugay, Mehmet I.; Tuncil, Yunus E.
    Due to its high antioxidant capacity, hazelnut (Corylus avellana L.) skin oil has recently gained great attention. However, its thermal and oxidative characteristics have not been elucidated yet. Here, we determined the thermal and oxidative properties, antioxidant activity and fatty acid composition of hazelnut skin oil (HSO) using differential scanning calorimetry (DSC), spectrophotometry and gas chromatography/mass spectrometry, respectively, and compared those with the oils from natural and roasted hazelnuts. HSO was found to have significantly higher proportions of polyunsaturated fatty acid, compared with oils from natural and roasted hazelnut. HSO had the lowest melting point. Moreover, HSO revealed higher oxidative stability, which can be attributed to its greater antioxidant capacity. These findings indicate that hazelnut skin, a by-product of hazelnut industry, has potential to be utilised in hazelnut oil industry to produce oil possessing high oxidative and thermal stability.