Master Degree / Yüksek Lisans Tezleri

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

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

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  • Master Thesis
    Investigations on the Effects of Carbon Sources and Ph on Exo-Polygalacturonase Productions by Aspergillus Sojae
    (Izmir Institute of Technology, 2013) Kuru, Gülten; Büyükkileci, Ali Oğuz
    Pectinases are a group of enzymes that are responsible for degredation of pectic substances. Pectinases are produced by many organisms including plants, bacteria and fungi. The aim of this study was to investigate the effect of different carbon sources and pH on pectinase production by a group of flamentous fungi. For this purpose, Aspergillus niger, Rhizopus oryzae ATCC 4858, Aspergillus sojae ATCC 2035 (A. sojae WT) and its mutant type Aspegillus sojae MT (A. sojae MT) grown in orange peel containing media were evaluated in terms of exo-polygalacturonase (exo-PG), pectin lyase (PL), pectin methyl esterase (PME), and also xylanase and cellulase activities. A. sojae WT and A. sojae MT were found to be as exo-PG producers. Maximum exo-PG activities were 47.84 U/ml and 108.02 U/ml, respectively. Exo-PG production by A. sojae WT and A. sojae MT was evaluated using the medium containing glucose, pectin, pectin/glucose, pectin/fructose and pectin/sucrose as substrate. Additional supply of glucose to the pectin media was found to be more effective than fructose or sucrose. The fermentations in which pH was not maintained, the use of glucose, pectin and pectin/glucose resulted in superior enzyme activities compared to ones obtained with other media compositions.
  • Master Thesis
    Transformation of Aspergillus Sojae With Vitreoscilla Hemoglobin Gene
    (Izmir Institute of Technology, 2010) Bardakçı, Betül; Tarı, Canan; Tari, Canan
    Aspergillus sojae known as koji mold is a non-aflatoxigenic fungus, designated with a GRAS status by FDA. This study considers the transformation of A. sojae with Vitreoscilla hemoglobin gene. Vitreoscilla hemoglobin is the bacterial hemoglobin, which enhances the oxygen transfer under microaerophilic conditions. Since industrial fungal fermentation with the high demand for oxygen are accounted to face oxygen limitations during the production of value added products like enzymes, antibiotics and organic acids; oxygen supply becomes an enormous problem to be solved by the manufacturers. To overcome this problem, an alternative solution using the vgb gene of Vitreoscilla and recombinant DNA technology and taking the A. sojae organism as model organism was proposed. The product of interest in this study was the exopolygalacturonase enzyme known to have wide applications in food, pharmaceutical, textile and paper industries. Here vgb gene was tried to be introduced to A .sojae via both protoplasting and electroporation methods. For transformation process vgb gene was cloned initially into plasmid ANIp4. For the selection of transformed A. sojae cells, uridine auxotrophic mutants were tried to be selected after UV mutagenesis. However, using a procedure based on selection of uridine supported growth did not result in A. sojae pyrG mutants. The success of transformation was initially observed by means of PCR analysis and agarose gel electrophoresis, later this was try to be confirmed by sequence analysis and agarose gel electrophoresis. However, due to the contamination problems accounted in the procedures the transformation with both methods could not be assured.
  • Master Thesis
    Production of Pectinase Enzyme From Aspergillus Sojae Batch and Fed-Batch Systems
    (Izmir Institute of Technology, 2008) Doğan, Nergiz; Tarı, Canan
    Commercial preparations of pectinases derived from fungi are well known to have high biotechnological value in the industry. For this purpose, polymethylgalacturonase (PMG) and polygalacturonase (PG) were produced with high productivities by Aspergillus sojae ATCC 20235 by using low cost carbon (Maltrin) and nitrogen (Corn Steep Liquor, CSL) sources. There is no literature report to best of our knowledge on the fed-batch production, purification and characterization of polygalacturonase using this microorganism.In this study batch fermentation was carried out in order to obtain the crude PG and to establish a baseline for the forth coming fed-batch experiments. The crude PG was partially purified using three-phase partitioning as an emerging bioseparation technique and characterized with respect to its biochemical and thermal properties. These studies showed that this enzyme holds a great potential to be a good candidate for various industrial applications. To optimize fed-batch fermentation conditions, response surface methodology (RSM) was performed using face-centered central composite design. As a result, maximum PG activity (20.61 U/ml) and maximum biomass (34.23 g/l) were obtained at high maltrin (150 g/l) and high CSL (10 g/l) concentrations when the repeated feeding was done at 48th and 72nd hours. Maximum PMG activity (16.76 U/ml) was also achieved at higher maltrin and higher CSL concentrations at a feeding time of 72nd hours. Fed-batch fermentation has been successfully used to increase PG (33.74%) and PMG (23.96%) activities from Aspergillus sojae. Finally, agar diffusion method was adapted as a rapid method for the selection of high pectinase producer in the strain improvement study.