Bu çalışmanın amacı, naturel fındık, kavrulmuş fındık ve fındık zarı diyet liflerinin (DL)
bileşimini ve yapısal özelliklerini karakterize etmek ve in vivo koşullarda kolonik mikrobiyota
bileşimi ve mikrobiyal metabolitler üzerindeki etkilerini incelemektir. Naturel fındık, kavrulmuş
fındık ve fındık zarı suda çözünen ve çözünmeyen DL'leri enzimatik olarak ekstrakte edilmiş ve
bileşimsel ve yapısal özellikleri, gaz kromatografisi/kütle spektrometrisi (GC/MS) kullanılarak
belirlenmiştir. GC/MS analizi, naturel ve kavrulmuş fındığın çözünmeyen DL'nin selüloz (%40-
47), ksiloglukan (%19-23), pektik polisakkaritler (%17-26) ve heteromannanlardan (%8-9)
oluştuğunu; fındık zarı DL’nin ise yaklaşık yarısının lignin, geri kalan kısmının ise selüloz (%50),
ksiloglukan (%17), pektik polisakkaritler (%23) ve heteromannandan (%3) oluştuğunu
göstermektedir. Öte yandan örneklerin suda çözünen DL’nin ise pektik polisakkaritler (%58-68),
ksiloglukan (%13-18) ve mannandan (%4.1-8.2) meydana geldiği belirlenmiştir. Daha sonra,
C57BL/6J ırkı fareler, 6 hafta boyunca fındık örneklerinden ekstrakte edilmiş DL ile
zenginleştirilmiş yemlerle beslenmiş ve kolonik mikrobiyota bileşimlerinde meydana gelen
değişimler, besleme sürecinin 0., 3. ve 6. haftasında toplanan dışkı örneklerinin 16S rRNA
sekanslama teknolojisi kullanılarak analiz edilmesiyle belirlenmiştir. Ayrıca, GC yardımıyla, kalın
bağırsakta oluşan mikrobiyal kısa- zincirli yağ asitleri (KZYA) haftalık olarak dışkı örnekleri
üzerinde ölçülmüştür. KZYA sonuçları, fındık DL'nin dişi farelerde bütirojenik, erkek
muadillerinde ise asetojenik etki gösterdiğini ortaya koymaktadır. Kolonik mikrobiyotanın
taksonomik karşılaştırmaları, fındık (özellikle naturel fındık) DL’nin probiyotik olarak bilinen ve
probiyotik potansiyeli olan Lactobacillus ile ilişkili OTU'ların nispi bolluklarını, diğer gruplara
kıyasla, daha fazla arttırdığını göstermiştir. LEfSe analizi, dişi fareler ele alındığında,
Lachnospiraceae, Prevotella, Ruminococcaceae ve Lactobacillus'un; erkek fareler ele alındığında
ise Bacteroides, Lactobacillus, Prevotella ve Lactococcus’un sırasıyla naturel fındık, kavrulmuş
fındık, fındık zarı ve kontrol (selüloz) grubu için biyobelirteç olduklarını ortaya koymuştur. Bu
sonuçlar, naturel ve kavrulmuş fındık ile fındık zarı DL'nin kolonik mikrobiyota bileşimi ve
mikrobiyal metabolitler üzerine etkilerinin cinsiyete özgü olduğunu ortaya koymaktadır. İlaveten,
bu sonuçlar kavurma işleminin fındık DL'nin fonksiyonel özelliklerinde kısmi değişime sebep
olduğunu, ancak genel olarak, fındık DL'nin faydalı mikroorganizmaların ve mikrobiyal
metabolitlerin bolluğunun artmasını sağlayarak, kolonik mikrobiyomu düzenlediğini açıkça
göstermektedir. Son olarak, bu sonuçlar, fındık zarı DL’nin, kolonda faydalı bakterileri teşvik etme
kabiliyetinde olduğunu ve dolayısıyla, fındık endüstrisi yan ürünü olan fındık zarının, prebiyotik
(veya benzeri) özellikte sindirilemeyen karbonhidratların üretimi için hammadde olarak kullanılma
potansiyeli olduğunu göstermektedir.,In this study, we aimed to characterize the compositional and structural features of dietary
fibers (DF) of natural hazelnut, roasted hazelnut, and hazelnut skin and further aimed to investigate
their impacts on colonic microbiota composition and function in vivo. Insoluble and soluble DF of
natural hazelnut, roasted hazelnut, and hazelnut skin were extracted using an enzymatic extraction
technique and their compositional and structural features were identified using gas chromatography
coupled with mass spectrometry (GC/MS). GC/MS analysis revealed that natural and roasted
hazelnut insoluble DF compose of cellulose (%40-47), xyloglucan (%19-23), pectic
polysaccharides (%17-26) and heteromannans (%8-9), whereas that of hazelnut skin compose of
lignin, cellulose, xyloglucan, pectic polysaccharides and heteromannans. On the other hand,
soluble DF of the samples were made up of pectic polysaccharides (%58-68), xyloglucan (%13-
18), and mannan (%4.1-8.2). Next, C57BL/6J mice were fed with chow diet containing the
extracted DF for 6 weeks, and changes that occurred in their colonic microbiota composition were
investigated using 16S rRNA sequencing technique on feces collected after 0, 3 and 6 weeks of
feeding period. Further, microbial metabolites as means of short-chain fatty acids (SCFA) were
measured on feces weekly using GC. SCFA analysis demonstrated that hazelnut DF show a
butyrogenic effect in female mice models, whereas acetogenic effect was observed in male
counterparts. Taxonomic comparisons of colonic microbiota revealed that hazelnut (especially
natural hazelnut) DF supplementation increase the relative abundances of Lactobacillus related
OTUs that are known to be probiotics or have probiotic potentials. LEfSe (linear discriminant
analysis effect size) analysis revealed that, for female mice, Lachnospiraceae, Prevotella,
Ruminococcaceae and Lactobacillus are discriminators for natural hazelnut, roasted hazelnut,
hazelnut skin and control groups, respectively; whereas for male mice, Bacteroides, Lactobacillus,
Prevotella and Lactococcus are discriminators for natural hazelnut, roasted hazelnut, hazelnut skin
and control groups, respectively. Our results revealed that DF of natural hazelnut, roasted hazelnut,
and hazelnut skin differentially impact the colonic microbiota composition and microbial
metabolites in a gender-specific way. Additionally, these results clearly indicate that, although
roasting process slightly impacts the functionalities (in terms of colonic microbiome) of hazelnut
DFs, hazelnut DFs generally modulate colonic microbiota by favoring beneficial microbes and
stimulating beneficial microbial metabolites. Further, this data suggest that, due to its ability to
promote beneficial microbes in the colon, hazelnut skin, a byproduct of the hazelnut industry, has
the potential to be used for the production of indigestible carbohydrates possessing prebiotic
function.
In this study, we aimed to characterize the compositional and structural features of dietary
fibers (DF) of natural hazelnut, roasted hazelnut, and hazelnut skin and further aimed to investigate
their impacts on colonic microbiota composition and function in vivo. Insoluble and soluble DF of
natural hazelnut, roasted hazelnut, and hazelnut skin were extracted using an enzymatic extraction
technique and their compositional and structural features were identified using gas chromatography
coupled with mass spectrometry (GC/MS). GC/MS analysis revealed that natural and roasted
hazelnut insoluble DF compose of cellulose (%40-47), xyloglucan (%19-23), pectic
polysaccharides (%17-26) and heteromannans (%8-9), whereas that of hazelnut skin compose of
lignin, cellulose, xyloglucan, pectic polysaccharides and heteromannans. On the other hand,
soluble DF of the samples were made up of pectic polysaccharides (%58-68), xyloglucan (%13-
18), and mannan (%4.1-8.2). Next, C57BL/6J mice were fed with chow diet containing the
extracted DF for 6 weeks, and changes that occurred in their colonic microbiota composition were
investigated using 16S rRNA sequencing technique on feces collected after 0, 3 and 6 weeks of
feeding period. Further, microbial metabolites as means of short-chain fatty acids (SCFA) were
measured on feces weekly using GC. SCFA analysis demonstrated that hazelnut DF show a
butyrogenic effect in female mice models, whereas acetogenic effect was observed in male
counterparts. Taxonomic comparisons of colonic microbiota revealed that hazelnut (especially
natural hazelnut) DF supplementation increase the relative abundances of Lactobacillus related
OTUs that are known to be probiotics or have probiotic potentials. LEfSe (linear discriminant
analysis effect size) analysis revealed that, for female mice, Lachnospiraceae, Prevotella,
Ruminococcaceae and Lactobacillus are discriminators for natural hazelnut, roasted hazelnut,
hazelnut skin and control groups, respectively; whereas for male mice, Bacteroides, Lactobacillus,
Prevotella and Lactococcus are discriminators for natural hazelnut, roasted hazelnut, hazelnut skin
and control groups, respectively. Our results revealed that DF of natural hazelnut, roasted hazelnut,
and hazelnut skin differentially impact the colonic microbiota composition and microbial
metabolites in a gender-specific way. Additionally, these results clearly indicate that, although
roasting process slightly impacts the functionalities (in terms of colonic microbiome) of hazelnut
DFs, hazelnut DFs generally modulate colonic microbiota by favoring beneficial microbes and
stimulating beneficial microbial metabolites. Further, this data suggest that, due to its ability to
promote beneficial microbes in the colon, hazelnut skin, a byproduct of the hazelnut industry, has
the potential to be used for the production of indigestible carbohydrates possessing prebiotic
function.
