Master Degree / Yüksek Lisans Tezleri

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Access type: Open accessSubject: search.filters.subject.Enzymatic hydrolysis

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  • Master Thesis
    Enhancement of Xylanase Activity in Xylooligosaccharide Production From Lignocellulosic Biomass
    (01. Izmir Institute of Technology, 2023) Büyükkileci, Ali Oğuz; Büyükkileci, Ali Oğuz; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Xylo-oligosaccharides (XOS) with prebiotic properties are obtained through xylan hydrolysis. Previously organosolv was found to be an effective pretreatment for XOS production from corncob. However, this process suffered from low XOS yields because of the limited hydrolysis of xylan in the pretreated biomass. This study was designed to test some approaches toward increasing the efficiency of xylanases on the organosolv-treated corncob. The two commercial enzymes (Shearzyme 500L and Veron 191S) used in this study showed a synergistic effect yielding higher XOS compared to single enzyme application. Partial removal of acetyl groups on the xylan in organosolv-treated corncobs enhanced XOS production significantly. The solid loading above 10% decreased XOS yield as it resulted in a highly viscous slurry that may have limited heat and mass transfer. Fed-batch addition of enzyme and biomass did not play a role in the improvement of hydrolysis. In sequential batch mode, the residual enzyme activity from the previous batch could release more XOS from the fresh biomass, though the yield was low. Addition of fresh enzymes to the previous hydrolysate together with biomass provided a more concentrated XOS solution (15.4 g/l) after the second batch. The addition of surfactants into the hydrolysis media to prevent enzyme binding to lignin did not improve XOS production. This study showed that organosolv could be considered an effective treatment for XOS production from corncob and the enzymatic hydrolysis could be improved by optimizing the conditions.
  • Master Thesis
    Potential of Deep Eutectic Solvent Pretreatment for Xylooligosaccharides Production From Corncob
    (01. Izmir Institute of Technology, 2023) Büyükkileci, Ali Oğuz; Büyükkileci, Ali Oğuz; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Enzymatic hydrolysis of xylan to produce xylooligosaccharides (XOS) requires pretreatment of the feedstock lignocellulosic biomass. The current pretreatments have some disadvantages, such as the use of harsh chemicals, high energy requirements, and impurity generation. This study aimed to develop a greener method for high-purity XOS production based on mild pretreatment of corncob and subsequent enzymatic hydrolysis. Both deep eutectic solvent (DES) and dilute alkali pretreatments provided approximately 65% lignin removal from the corncob, while 80% of the xylan remained in the solid. When corncob was treated with DES at 130 ○C for 2 h, the total XOS yield in the hydrolysis was 44.1%, and the yield of xylotriose and xylobiose (LDP XOS) was 39.7% based on feedstock xylan. Dilute alkali treatment of corncob at 30 oC for 8 h, provided a total XOS yield and LDP XOS yields of 41.6% and 33.4%, respectively. The enzyme was removed from the XOS solution, while most of the LDP XOS was recovered, using the ultrafiltration system with a 10 kDa membrane. Fermentable sugars were produced from the spent solids as a secondary product using cellulase hydrolysis. This study suggested that DES and dilute alkali-based processes can be considered an eco-friendly approach to XOS production. Since XOS was mostly composed of LDP XOS, they can be preferred as food additives.