Master Degree / Yüksek Lisans Tezleri

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Department: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Food EngineeringSubject: search.filters.subject.Polygalacturonase

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  • Master Thesis
    Effect of the Morphology of Aspergillus Sojae on Pectinase Enzyme and the Optimization of Fermentation Conditions
    (Izmir Institute of Technology, 2006) Göğüş, Nihan; Tarı, Canan; Tarı, Canan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The control of the morphology of fungi needs great attention for the optimal potential production of the product. For this purpose Aspergillus sojae ATCC 20235, which has no available literature report on the pectinase production, is used as a model in the determination of the optimum regions for maximum polygalacturonase synthesis and biomass formation with desired pellet morphology by using low cost carbon and nitrogen sources. Firstly, a full factorial statistical design, with the factors of, two taxonomically different strains, seven types of seed culture formulations (slants) and two types of fermentation media were used to investigate the effect of these parameters on the polygalacturonase (PG) production. According to statistical analysis, factors of strain types and fermentation media and the interaction between them were found significant on the enzyme activity. Aspergillus sojae in a complex media, inoculated with a seed culture prepared from molasses resulted in maximum PG activity (0.2 U/ml). Then, a two step optimization procedure with four factors (concentrations of maltrin and corn steep liquor (CSL), agitation speed and inoculation ratio) was used to investigate the effect of these parameters on the PG activity, mycelia growth (biomass) and morphology (pellet size) of Aspergillus sojae. According to the results of response surface methodology (RSM), concentrations of maltrin, CSL and agitation speed were significant (p<0.05) on both PG synthesis and biomass formation. As a result, maximum PG activity (13.5 U/ml) was achievable at high maltrin (120 g/l), low CSL (0 g/l), high agitation speed (350 rpm) and high inoculation ratio (2x107 total spore). The diameter of pellets ranged between 0.05-0.63 cm. The second optimization step improved the PG activity by 74 % and the biomass by 40 %. Furthermore characterization of the enzyme with respect to its optimum pH and temperature and the effect of these on the stability were considered. Determination of the thermal inactivation constant with its inactivation energy and the substrate specificity constant were estimated.
  • Master Thesis
    Investigation of the Effects of Dissolved Oxygen Concentration, Aeration and Agitation on the Morphology and Rheology in Submerged Fungal Fermentation
    (Izmir Institute of Technology, 2007) Öncü, Şelale; Ünlütürk, Sevcan; Ünlütürk, Sevcan; 03.08. Department of Food Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    The effects of pH, agitation speed, dissolved oxygen tension (DOT) and aeration, significant in common fungal fermentations, on the production of polygalacturonase (PG) enzyme and their relation to morphology and broth rheology were investigated in a batch bioreactor using Aspergillus sojae which has no available literature report on the pectinase production. All four factors were effective on the response parameters under study. An uncontrolled pH increased biomass and PG activity by 27% and 38%, respectively compared to controlled pH (pH 6). pH did not significantly affect the broth rheology but created an impact on the pellet morphology. Similarly, the maximum biomass obtained at 500 rpm and at 30h was 3.27 and 3.67 times more than at 200 and 350 rpm, respectively. The maximum enzyme productivity of 0.149 U ml-1 h-1 was obtained at 200 rpm. Non . Newtonian and pseudoplastic broth rheology was observed at 500 rpm agitation speed. Furthermore, a DOT range of 30-50% was essential for maximum biomass formation, whereas only 10% DOT was required for maximum PG synthesis. Non . Newtonian shear thickening behavior (n>1.0) was depicted at DOT levels of 10% and 30%, whereas, non-Newtonian shear thinning behavior (n<1.0) was dominant at 50% DOT. When 2.5 l/min aeration experiment was investigated detaily; it was determined that at about 21st hour, polygalacturonase production approaches its maximum (1.49 U) and pellets are smaller, high in number. At 48th hour; polygalacturonase production declines to zero, biomass reaches its maximum and pellets are big (average pellet size is 1.94±0.58 mm) and fluffy with compact centers. At the end of fermentation (96.hour), fermentation medium is close to Newtonian. The overall fermentation duration (50-70h) was considerably shorter as opposed to common fungal fermentations revealing the economic feasibility of this particular process. As a result this study not only introduced a new strain with a potential of producing a highly commercially significant enzyme but also provided certain parameters significant in the design and mathematical modelling of fungal bioprocesses.