Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Şanlı Mohamed, GülşahSubject: search.filters.subject.Enzymes

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Now showing 1 - 5 of 5
  • Master Thesis
    The Effect of Enzyme Use on the Formation of Carbonyls and Structural Properties of Cakes
    (01. Izmir Institute of Technology, 2021) Ceylan, Çağatay; Er, Ayşe Ege; Şanlı Mohamed, Gülşah; Ceylan, Çağatay; Şanlı Mohamed, Gülşah; 01. Izmir Institute of Technology; 03.08. Department of Food Engineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science
    Enzymes are used as additives to improve the quality parameters of cakes. However, high temperature conditions produce carbonyl-containing compounds as precursors of toxic maillard reaction products. In this study three food grade enzymes were used as agents to decrease the formation of carbonyl-containig compounds while preserving the cake quality factors. For this purpose transglutaminase, lipase and amylase enzymes were used. All of the three enzymes lowered the amounts of carbonyls with the largest decrease by lipase of 31.83% (p<0.05) with respect to the control cake. Transglutaminase and lipase addition changed the carbonyl profile of cakes. Both transglutaminase and lipase caused important changes in protein secondary structures with large increases in alpha helix, turns and anti-parallel beta structures, however, amylase did not cause such large changes. The three enzymes used caused the lipid/protein ratio to decrease. The level of lipid unsaturation did not change for transglutaminase and lipase, however, the level unsaturation decreased in the case of amylase indicating the formation of dicarbonyls was via Maillard reaction not due to lipid peroxidation. However, the GC-MS analysis results indicated that there was no change in the formation of neither the Maillard reaction products nor the lipid oxidation products in the head space analysis. The amorphous structure of the starch in cake samples increased depending on the enzyme concentration used.
  • Master Thesis
    Optimization of Expression and Isolation of a Thermophilic P450 Enzyme
    (Izmir Institute of Technology, 2018) Aslantaş, Yaprak; Sürmeli, Nur Başak; Şanlı Mohamed, Gülşah; Sürmeli, Nur Başak; Şanlı Mohamed, Gülşah; 03.01. Department of Bioengineering; 04.01. Department of Chemistry; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Cytochrome P450 enzymes (CYP or P450) are monooxygenases that catalyze the oxidation of hydrocarbons with high efficiency and selectivity, and many other reactions like hydroxylation, epoxidation, reduction, demethylation. CYP119, is a thermophilic P450 from Sulfolobus acidocaldarius. Thanks to thermophilic properties, CYP119 has potential to be widely used as a biocatalyst in production of fine chemicals and pharmaceuticals. However, production and purification of CYP119s is quite difficult and time consuming. Here, through recombinant protein production techniques, the optimum production and purification of heat-tolerant CYP119 has been successfully carried out. N-terminal and C-terminal histidine tags were cloned to CYP119. Protein expression was induced in Escherichia coli BL21 (DE3) cells with isopropyl β-D-1-thiogalactopyranoside (IPTG). δ-aminolevulinic acid (ALA) was also used to increase the heme biosynthesis. Different IPTG and ALA concentrations, expression temperature and duration were used to optimize production. CYP119 was isolated and purified with Ni-NTA affinity column. The thermostability of purified N (N-His-CYP119) and C (C-His-CYP119) terminal His-tagged were compared with wild type CYP119 (Wt-CYP119). Oxidation reaction of CYP119 and variants carried out and compared at 25 °C and 65 °C. Also, epoxidation of styrene was performed with N-His-CYP119 in different temperatures. The effects of histidine tags on stability and activity of the CYP119s were observed. Here, conditions for the production of CYP119 were optimized and the histidine tags were found to cause changes in stability and function of proteins. This project will lead to increase in the production of the important enzyme CYP119, which will increase its utilization in the industry.
  • Master Thesis
    Immobilization of Thermophilic Esterase on Magnetic Cornstarch Nanoparticles for Biological Applications
    (Izmir Institute of Technology, 2016) Öz, Yasin; Şanlı Mohamed, Gülşah; Şanlı Mohamed, Gülşah; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In last three decades, even the role of enzymes for biological and industrial applications has become more worthy, enzymes also have some defects. The enzyme immobilization allows to overcome these defects by improving abilities of reusing of catalysts by multiple times, easier reactor operation and product separation. Due to its potential use in biological and industrial applications, isolated thermophilic esterase from Geobacillus sp. was immobilized on magnetic cornstarch nanoparticles. In order to determine activity performance of immobilized enzyme, the effects of temperature, pH and some chemicals on enzyme activity were investigated. The results have shown that after immobilization, the relative activity of immobilized esterase has increased to 80% at 80 0C in comparison to free esterase. Therewithal, the reusability of immobilized esterase has increased fourfold in comparison to free esterase. The magnetic character of the support media has brought ease to separate biocatalysts from reaction media.
  • Master Thesis
    Purification and Biochemical Characterization of Xylanase Expressed in Thermophilic Geobacillus Sp.
    (Izmir Institute of Technology, 2015) Köksal, Mustafa; Köksal, Mustafa; Şanlı Mohamed, Gülşah; Şanlı Mohamed, Gülşah; Köksal, Mustafa; 04.03. Department of Molecular Biology and Genetics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Xylanase is an enzyme that catalyzes the degradation of the linear polysaccharide β-1,4-xylan into xylose and breaks down the hemicellulose structure of plant cell wall. The xylanolytic property of the enzyme makes it preferable for many biotechnological applications in industry. This enzyme is possibly produced by some bacterial and fungal microorganisms. In this study, briefly, xylanase enzyme was expressed in thermophillic Geobacillus sp. and purified by cold acetone precipitation and gel filtration chromatography. Molecular weight of our xylanase was found as 40.1 kDa by SDS-PAGE and this protein band was verified by Native-PAGE activity staining. Finally, it was characterized using biochemical methods. For characterization studies, Km and Vmax values were calculated from Lineweaver-Burk plot as 10.2 mg/ml and 31.7 U/ml, respectively. The optima temperature and pH for enzyme activity were investigated using beechwood xylan as substrate and found as 55°C and 8.0, respectively. Furthermore, effects of some metal ions, various chemical reagents and organic solvents on enzyme activity were also determined and we observed that Ca2+, Mn2+ and Co2+ affected the activity positively while Zn2+, Cd2+, Fe3+, EDTA, SDS, CHAPS and DTT shielded the activity. And only β-mercaptoethanol caused a significant change amoung organic solvents. Lastly, that the enzyme has a long shelf-life was confirmed assaying the samples taken from enzyme stocks stored at +4°C and room temperature for six weeks.
  • Master Thesis
    Molecular Cloning, Overexpression and Biochemical Characterization of Bacterial Amylase for Biotechnological Processes
    (Izmir Institute of Technology, 2012) Burhanoğlu, Tülin; Şanlı Mohamed, Gülşah; Karakaya, Hüseyin Çağlar; Karakaya, Hüseyin Çağlar; Şanlı Mohamed, Gülşah; 04.03. Department of Molecular Biology and Genetics; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Amylases are the enzymes that act on glycosidic bond of starch and related polysaccarides. They comprise 25% of enzyme utilised in a variety of industry. It is used to obtain maltose, glucose and maltodextrins in various lenghts during industrial processes. Amylases are widely distributed enzymes in bacteria, fungi, higher plants and animals. Thermophilic enzymes are widely demanded in order to be stable at harsh process conditions. Isolating these enzymes from thermophilic microorganism is increasing trend because of ease of enzyme production. In this study α-amylase gene region from a thermophilic Bacillus sp. isolated from Balçova Geotermal region in İzmir was cloned to compotent E. coli BL 21 cells. Additionally protein expression was reinforced with pKJE7 chaperone plasmid. Cloned gene was sequenced and found as 1542 bp in length. Thermophilic amylase that has a 59.9 kD molecular weight was expressed and purified from this recombinant strain. Mass spectrometric analysis were performed and the enzyme was matched with α-amylase family protein of Geobacillus thermodenitrificans NG80-2 using NCBInr database. The aminoacid sequence of this enzyme was seen to be similar 92% with our obtained enzyme. According to the results of characterization studies, the amylase enzyme was seen to have highest activity at pH 8.0 and 60°C. The enzyme was also showed to have resonable activity between pH5 and 9. 85% of the enzyme activity was retained at 70°C. Furthermore, amylase activities at 65 and 85°C were observed to remain stable for 5 and 2 hours, respectively. It was also showed that the activity was stable and pH7 and 9 for 6 hours. The effects of some metal ions, chemical agents and organic solvents on enzyme activity were examined so, Co+2, Mg+2,Ca+2 was determined to be as inducer for the enzyme activity. Conversely the activity was inhibited by Cu+2. Furthermore methanol, DDT and Triton X-100 was found to have no effect on the enzyme activity.