Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 19Citation - Scopus: 20Processing of Hazelnut (corylus Avellana L.) Shell Autohydrolysis Liquor for Production of Low Molecular Weight Xylooligosaccharides by Aureobasidium Pullulans Nrrl Y-2311 Xylanase(Elsevier, 2021) Sürek, Ece; Büyükkileci, Ali Oğuz; Yeğin, SırmaIn this study, a versatile process for the production of xylooligosaccharides (XOS) with a low degree of polymerization (DP 2-6) from hazelnut shells was designed. This process included autohydrolysis integrated with sequential enzymatic hydrolysis by crude xylanase produced with Aureobasidium pullulans NRRL Y-2311-1 from wheat bran. Autohydrolysis of hazelnut shells was carried out at a solid:liquid ratio of 1:6 (w/w) and 190 degrees C nonisothermally. The effects of several parameters on enzymatic hydrolysis of the autohydrolysis liquor were determined. The maximum XOS (DP 2-6) production was 22.5 g/L which was obtained at pH 5.0 and 40 degrees C using enzyme concentration of 240 U/g XOS and substrate concentration of 72 g/L. Under these conditions, 31.29 % of the substrate (total XOS) was converted to low-DP-XOS; xylobiose and xylotriose are being the major oligomers. This is the first study on the application of A. pullulans xylanase in production of xylooligomers from hazelnut shells.Article Citation - WoS: 73Citation - Scopus: 77Utilization of Xylan-Type Polysaccharides in Co-Culture Fermentations of Bifidobacterium and Bacteroides Species(Elsevier, 2020) Zeybek, Nüket; Rastall, Robert A.; Büyükkileci, Ali OğuzAlthough most members of the genus Bifidobacterium are unable to utilize xylan as a carbon source, the growth of these species can be induced by this polysaccharide in the gut environment. This indicates a requirement for an association between Bifidobacterium species and some other members of gut microbiota. In this study, the role of cross-feeding between Bifidobacterium and Bacteroides species in the bifidogenic effect of xylan was investigated using in-vitro pure and co-culture fermentations. The pure culture studies showed that among the Bifidobacterium species tested, only Bifidobacterium animalis subsp. lactis was able to utilize xylooligosaccharides. The co-culture of this strain with Bacteroides species enabled it to grow in the presence of xylan. These results suggest that the ability of Bacteroides species to hydrolyze xylan could allow the proliferation of specific Bifidobacterium species in the gut through substrate cross-feeding.Article Citation - WoS: 40Citation - Scopus: 45Comparison of Liquid Hot Water, Very Dilute Acid and Alkali Treatments for Enhancing Enzymatic Digestibility of Hazelnut Tree Pruning Residues(Elsevier, 2018) Sabancı, Kevser; Büyükkileci, Ali OğuzThe effect of pretreatments on the composition of the hazelnut tree pruning residue (HTPR) and on the digestibility of the cellulose was investigated. The liquid hot water (LHW) and the very dilute acid (VDA) treatments were effective in solubilizing hemicellulose. The cellulose conversion increased up to around 60% (corresponding to 32–36 g/L glucose) with decreasing hemicellulose concentration in the pretreated HTPR. The alkali treatment provided partial delignification, however, the glucose production was comparably lower. Combining the hemicellulose removal and the delignification effect of different pretreatments in two-stage processes (LHW-alkali and VDA-alkali treatments) enhanced the cellulose concentration in the solids, but not the amount of glucose released in the enzymatic digestion. These results suggested that the hemicellulose was the main barrier against the conversion of cellulose in the LHW and VDA treated HTPR and the glucose in the hydrolysis medium inhibited the cellulase activity, which prevented the complete conversion of cellulose.