Master Degree / Yüksek Lisans Tezleri

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

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Subject: search.filters.subject.Chitin--Biotechnology

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  • Master Thesis
    Production and Isolation of Fungal Chitosan by Submerged Fermentation
    (Izmir Institute of Technology, 2003) Alper, Seda; Harsa, Hayriye Şebnem
    Chitosan is the N-deacetylated derivative of chitin which is the supporting material of crustaceans and insects. Chitosan together with chitin are recommended as suitable functional materials because of their excellent biocompatibility, biodegradability, non-toxicity and adsorption properties and can be used in agriculture, biotechnology and food industry. Although chitosan is produced by chemical deacetylation of chitin molecule, it is also a natural component of cell walls of fungi belonging to Zygomycetes and can be produced by extraction from fungus cell walls. Fungi are thus the promising alternative sources of chitosan. Fungi can be manipulated to give chitosan of more consistent and desired physico-chemical properties compared to chitosan obtained from crustacean sources. In this study, Absidia spp, Aspergillus niger, Rhizopus arrhizus, Cunnighamella elegans, and Mucor rouxii were examined for biomass growth. At first, all five species were grown on synthetic medium at 28 C, 180 rpm in shake-flask incubator. Mucorrouxii which gave the maximum biomass concentration was also grown on molasses. The maximum biomass concentration of Mucor rouxii was found to be higher than that of synthetic medium. The best growth conditions obtained were 4% sucrose, 0.2% yeast extract, 1% peptone and 106 spores in 40 ml. The mycelia harvested at late exponential phase was treated with alkali to remove proteins and chitosan was extracted from cell wall by using acetic acid. The yield of extractable chitosan obtained from cell wall of Mucor rouxii was 2500 mg / l and it is almost 20 % of biomass and approximately 35 % of alkali insoluble fraction.
  • Master Thesis
    Preparation and Characterization of Chitosan/Calcium Phosphate Based Composite Biomaterials
    (Izmir Institute of Technology, 2004) Yıldırım, Oktay; Çiftçioğlu, Muhsin
    In this study the preparation and characterization of three-dimensional chitosan-calcium phosphate composite structures and porous hydroxyapatite bodies for biomaterial applications have been studied. The effects of chitosan calcium phosphate amount on density, porosity, microstructure, chemical composition and mechanical properties on the composites and effects of porosifier contents, hydroxyapatite content of the slurry and sintering temperature on density, porosity and microstructure of the porous ceramic samples were investigated. SEM was used for microstructural analysis, XRD and FTIR were used for chemical analysis, Archimedes method was used for investigating physical properties and compression test for investigating mechanical properties. In this study low molecular weight chitosan, -tricalciumphosphate, hydroxyapatite and hydroxyapatite whisker have been used. For composites freeze drying technique and for the porous bodies dry pressing, polymer sponge method and dough method have been used.The densities of the composites prepared by using chitosan as the matrix and hydroxyapatite, hydroxyapatite whisker, and B-tricalciumphosphate as reinforcement increased and the porosities decreased with the increase in the ceramic content. The modulus of elasticity and the yield stress generally increased with the increasing ceramic content except for the chitosan/-tricalciumphosphate composites. The densities and porosities of the composite structures varied in the range of 0.059-0.29 g/cm3 and 96-88% respectively. The elastic moduli of the composites varied in a range of 4.45-10.09 MPa and yield stress varied in a range of 0.14-0.34 Mpa due to the change in the ceramic weight%. Changing the ceramic weight% also had influence on the microstructure. Generally with increasing ceramic content the pore sizes decreased.The pore sizes varied in a range between 100-250, 100-400 and 100-200 for chitosan/hydroxapatite, Chitosan/-TCP/Hydroxyapatite and chitosan/HA whisker composites respectively. FTIR and XRD analysis showed that the composite structures contained original constituents, no new chemical compounds were formed the production process had not affected crystallinity of ceramic phases. The densities of the porous ceramic bodies decreased and the porosities increased with the increasing porosifier content at the porous ceramics prepared by dough method and dry pressing method. The porosity and density values of porous hydroxyapatite samples changed in range of 34-72% and 2.03 to 0.87 g/cm3. Pore sizes of polymeric sponge samples were found to be around 300-400 and dry pressing and dough method samples were found to be 10u.