Yazar "Sagiroglu, A" seçeneğine göre listele
Listeleniyor 1 - 8 / 8
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Bioconversion of methanol to formaldehyde(Informa Healthcare, 2005) Sagiroglu, A; Yavuz, MOModified methylotrophic yeast Hansenula polymorpha (HP A16) was used in this study, which was obtained with recrossing a leucine oxotrophic yeast and a wild type Hansenula polymorpha CB4732 and was discovered by Ogata et al. [1]. The yeast is grown with methanol as a sole carbon source in which methanol oxidase (MOX) is a key enzyme of methanol metabolism. Because of its stability and low substrate specificity, alcohol oxidase is of considerable interest for a range of biotechnological processes. Various methanol feeding regimes were evaluated in an effort to increase the biomass concentration and productivity that could be achieved from fermentations using the other Hansenula polymorpha species. This yeast was grown by batch fermentation. The effects of conditions of inoculation media for increasing amount of MOX enzyme in peroksizomes of yeast with MOX activity were observed. The highest MOX activity of yeast was found within optic density of grown media of OD600 1.5, at 0.35 mu M of methanol as used an oxotrophic substrate, at 35 degrees C temperature, at pH 7.0 of 0.1 M potassium phosphate buffer (KPB), at 40 mu L of buffered yeast cell volume and at the incubation time of 50 minutes. Whole yeast cells were cultivated at above optimized incubation conditions. The cells were immobilized within the polyacyrlamide gels by entrapment method. Free whole cells and immobilized whole cells were compared using bioconversion percentages of methanol to formaldehyde.Öğe Immobilization of lipases on different carriers and their use in synthesis of pentyl isovalerates(Taylor & Francis Inc, 2004) Sagiroglu, A; Telefoncu, APorcine pancreatic lipase (PPL) and Candida cylindracea lipase (CCL) were immobilized on Celite and Amberlite IRA 938 by deposition from the aqueous solution by the addition of hexane. The influence of the immobilization on the activities of the immobilized lipase derivatives has been studied. The immobilized lipases were used in synthesis of pentyl isovalerates. Various reaction parameters affecting the synthesis of pentyl isovalerates were investigated. The reaction rates were compared with the rates of esterification with free lipases. The immobilized lipases were found to be very effective in the esterification reaction. The lipases immobilized on Celite 545 exhibited better operational stabilities than that of immobilized on Amberlite IRA-938.Öğe Non-covalent immobilization of quince (Cydonia oblonga) polyphenol oxidase(Tubitak Scientific & Technological Research Council Turkey, 2002) Yagar, H; Sagiroglu, AA partially purified polyphenol oxidase from quince (Cydonia oblonga) was immobilized on bentonite by simple adsorption at pH 6.8. The properties of the immobilized enzyme were compared to those of the free enzyme. Optimum pH and temperature were determined to be 9.0 and 45degreesC, respectively, showing the alteration of pH and temperature profiles by immobilization. No drastic change was observed in the K-m value after immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrates. Thermal and storage stability and reusability experiments were carried out. It was observed that the immobilized enzyme had storage stability for a period of one year but had no reusability in the batch process.Öğe Non-covalent immobilization of quince (Cydonia oblonga) polyphenol oxidase on alumina(Slovensko Kemijsko Drustvo, 2002) Yagar, H; Sagiroglu, APolyphenol oxidase enzyme purified partially from quince (Cydonia oblonga) was immobilized on alumina (Al2O3) by simple adsorption at pH 6.8. The properties of immobilized enzyme were compared to those of the free enzyme. Optimum pH (8.5) and temperature (45 degreesC) were determined, showing the alteration of pH and temperature profiles by immobilization. Catechol, L-DOPA, p-cresole and pyrogallol were tested as substrate and it was established that affinity was highest for catechol. K-m constant was 5 mM for catechol. Thermal and storage stability were carried out. It was observed that the immobilized enzyme had storage stability for a period of one year.Öğe Partially purification and characterization of polyphenol oxidase of quince(Scientific Technical Research Council Turkey, 2002) Yagar, H; Sagiroglu, APolyphenol oxidase (PPO, EC 1.14.18.1) was extracted from quince (Cydonia oblonga) by using 0.1 M phosphate buffer, pH 6.8. The polyphenol oxidase of quince was partially purified by (NH4)(2)SO4 and dialysis. Substrate specificity experiments were carried out with catechol, pyrogallol, L-DOPA, p-cresole and tyrosine. Catechol was the most suitable substrate compound for quince PPO. The Michaelis constants were 4.54 mM, 7.35mM and 17.8 mM for catechol, pyrogallol and L-DOPA, respectively at 25degreesC. The optimum pH and temperature were determined with the specific substrate catechol as 8.0 and 40degreesC, respectively. Of eight inhibitors tested L-cysteine, ascorbic acid and potassium cyanide were the most effective against quince PPO.Öğe Preparation and properties of lipases immobilized on different supports(Informa Healthcare, 2004) Sagiroglu, A; Kilinç, A; Telefoncu, APorcine pancreatic lipase and Candida cylindracea lipase were immobilized on Celite and Amberlite IRA-938. Activities and stabilities of immobilized lipases were investigated. The immobilized lipase derivatives on Celite exhibited grater residual activity and more resistance to thermal inactivation than their immobilized counterpart on Amberlite IRA-938. The apparent optimum temperatures of the immobilized lipases were 7-10degreesC higher than that of the free enzymes. The native lipase and lipases immobilized on Celite showed same behaviors of pH dependence. But the pH optimum values for lipases immobilized on Amberlite IRA-938 were shifted to the acidic region relative to that of free enzymes. The stabilities of free and immobilized lipases were also investigated.Öğe Sunflower seed lipase: Extraction, purification, and characterization(Taylor & Francis Inc, 2005) Sagiroglu, A; Arabaci, NA simple procedure for the extraction of the lipolytic activity from sunflower seed has been developed. Various conditions of extraction have been optimized in order to obtain maximum yield of lipase. A new lipase enzyme was purified by the fractional salt precipitation from the supernatant, dialysis on a cellulose membrane. and gel column chromatography on Sephadex G-75. The lipase was monomeric. with an apparent M, of 22 kDa and a pI of 8, with the electrophoretic analysis. Kinetics of the enzyme activity versus substrate concentration showed typical lipase behavior. with K-m and V-max values of 1.33 mM and 555 U/mg. All trialycerides were efficiently hydrolyzed by the enzyme, but this showed a preference towards triglycerides of natural mono unsaturated fatty acids. The optimum temperature. pH. and incubation time for lipolytic activity were 50degreesC, 7.5, and 5 min, respectively. The stability of the sunflower lipase was investigated under operational and storage conditions. It was found that this enzyme preserved its lipolytic activity at temperatures between at 35-50degreesC, alkaline pH, and for a period of about four months.Öğe Trypsin-catalyzed peptide synthesis in acetonitrile with low water content(Tubitak Scientific & Technological Research Council Turkey, 2002) Yesiloglu, Y; Sagiroglu, ATrypsin was immobilized to alumina by adsorption from its aqueous solutions. The activity of trypsin was increased by immobilization for peptide synthesis. With these immobilized enzymes Bz-Arg-Leu-NH2 dipeptide synthesis was carried out. Iso amylalcohol, tetrahydrofuran and acetonitrile were used as solvents giving the highest yield in the peptide formation reaction. The yield of the peptide was strongly dependent on water content in the reaction medium. The stability of alumina-immobilized trypsin is described.
