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Öğe Aspartic proteinases from Mucor spp. in cheese manufacturing(Springer, 2011) Yegin, Sirma; Fernandez-Lahore, Marcelo; Salgado, Antonio Jose Gama; Guvenc, Ulgar; Goksungur, Yekta; Tari, CananFilamentous fungi belonging to the order of Mucorales are well known as producers of aspartic proteinases depicting milk-clotting activity. The biosynthesis level, the biochemical characteristics, and the technological properties of the resulting proteinases are affected by the producer strain and the mode of cultivation. While the milk-clotting enzymes produced by the Rhizomucor spp. have been extensively studied in the past, much less is known on the properties and potential applications of the aspartic proteinases obtained for Mucor spp. Indeed, several Mucor spp. strains have been reported as a potential source of milk-clotting enzymes having unique technological properties. Both submerged fermentation and solid substrate cultivation are proven alternatives for the production of Mucor spp. aspartic proteinases. This review provides an overview on the bioprocessing routes to obtain large amounts of these enzymes, on their structural characteristics as related to their functional properties, and on their industrial applications with focus on cheese manufacturing.Öğe Bioprocess strategies for production of xylanase on agro-residual products with Aureobasidium pullulans(Elsevier Science Bv, 2014) Yegin, Sirma; Sargin, Sayit; Goksungur, YektaÖğe Citric acid production by a novel autochthonous Candida zeylanoides isolate: optimization of process parameters(Springer, 2022) Borekci, Bilge Sayin; Kaya, Mukerrem; Goksungur, Yekta; Kaban, GuzinIn this study, citric acid (CA) production by autochthonous Candida zeylanoides 7.12 was investigated and optimized. Response surface methodology (RSM) was used for the analysis of simultaneous effects of the chosen factors and 2 experiment designs were applied. In the first experimental design, the effects of initial pH value (5.5, 6.0 and 6.5), fermentation time (4, 5 and 6 days) and initial glucose concentration (125, 150 and 175 g/L) on CA production were investigated. Initial pH value was adjusted periodically with NaOH. Results of the statistical analysis showed that the model was found to be not applicable sufficiently to the chosen data. A second experimental design was employed at the same levels of glucose concentration and fermentation time by disabling the pH factor. pH level was kept at 6.5 with CaCO3. Results of the statistical analysis showed that the fit of the model was good and the lack of fit was not significant (P > 0.05). The highest CA concentration of 11.36 g/L was obtained after 6 days of fermentation with an initial glucose concentration of 125 g/L. The results indicated that initial glucose concentration and fermentation time were important parameters for CA production by C. zeylanoides 7.12 and this strain could be used for future studies.Öğe Comparison of pullulan production performances of air-lift and bubble column bioreactors and optimization of process parameters in air-lift bioreactor(Elsevier Science Bv, 2014) Ozcan, Emrah; Sargin, Sayit; Goksungur, YektaThe production of pullulan from synthetic medium by Aureobasidium pullulans DSM-2404 in air-lift and bubble column bioreactors was investigated. The kinetics of polysaccharide, pullulan and biomass production were determined. Maximum effective yield (g pullulan produced g(-1) initial sugar) obtained in air-lift bioreactor (Y-P/S = 0.402) was found to be higher than that obtained in bubble column bioreactor (Y-P/S = 0.342). Response surface methodology was used to investigate the effects of three factors (initial sugar concentration, aeration rate and incubation time) on the concentration of pullulan in air-lift bioreactor for batch cultures of A. pullulans. No previous work has used statistical analysis in determining the interactions among these variables in pullulan production in an air-lift bioreactor. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar concentration, aeration rate and incubation time had a strong linear effect on pullulan concentration. Moreover, pullulan concentration was significantly influenced by the negative quadratic effects of the given variables and by their positive or negative interactions except the interaction between initial sugar concentration and incubation time (P > 0.05). Maximum pullulan concentration of 38.77 g/L was obtained at the optimum levels of process variables (initial sugar concentration 95.2 g/L, aeration rate 1.93 vvm and incubation time 5.36 days) (C) 2014 Elsevier B.V. All rights reserved.Öğe THE EFFECT OF MICROBIAL LEVAN ON THE GROWTH OF MICROORGANISMS: INHIBITORY OR STIMULATORY?(Parlar Scientific Publications (P S P), 2020) Gokmen, Gokhan Gurur; Silbir, Selim; Goksungur, Yekta; Kisla, DuyguThe objective of this study research is to investigate the effect of microbial levan polymer on the growth of some bacteria and fungi. Levan produced by Zymomonas mobilis NRRL B-14023 and commercial levan produced by Bacillus subtilis were used for this purpose. the 96-well microplate broth-dilution and broth macrodilution methods were used to determine the antibacterial and antifungal activity of levan polymers on selected bacteria, yeast and mould cells. Minimum inhibitory concentration (MIC) values could not be determined for both levan types because microbial growth was detected even at the highest levan concentration of 40 mg/ml. This study showed that some microorganisms were inhibited while others stimulated with levan polymer added to their growth media.Öğe Exergy analysis of wine production: Red wine production process as a case study(Pergamon-Elsevier Science Ltd, 2017) Genc, Mahmut; Genc, Seda; Goksungur, YektaThis paper performs exergy analysis of a red wine production line and defines the exergy destruction rates to assess the system performance in terms of sustainability. A model study with necessary data is chosen for the calculations. The total exergy destruction rate of the overall system was determined to be 344.08 kW while the greatest destruction rate of the exergy in the whole system occurred in the open fermenter (333.6 kW). The system thermal efficiency was obtained to be 57.2% while the exergy efficiency was calculated as 41.8%. The total exergy destruction rate of the overall system increases With the increase both in the grape flow rate and the reference temperature when the reference pressure is assumed as 101.325 kPa. Furthermore, the chemical exergy of streams was found much higher than the physical exergy for each stream. The exergy results were illustrated through the Grassmann diagram. Furthermore, cumulative exergy loss and specific exergy loss values were determined as 2692.51 kW/1 kg/s grape processed and 5080.20 kW/kg wine, respectively. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Exploitation of Agricultural Wastes and By-Products for Production of Aureobasidium pullulans Y-2311-1 Xylanase: Screening, Bioprocess Optimization and Scale Up(Springer, 2017) Yegin, Sirma; Buyukkileci, Ali Oguz; Sargin, Sayit; Goksungur, YektaThe potential of several agricultural wastes and by-products (wheat bran, oat bran, corn cob, brewer's spent grain, malt sprout, artichoke stem, sugar beet pulp, olive seed, cotton stalk and hazelnut skin) was examined as the substrate for xylanase production by Aureobasidium pullulans Y-2311-1. Based on the screening studies, wheat bran was selected as the best substrate for further optimization studies. The effects of initial medium pH, temperature and incubation time on xylanase production in shake flask system were optimized by response surface methodology (RSM). The optimum levels of the process variables defined by the model (initial medium pH, 4.24; temperature, 30.27 degrees C; and incubation time 126.67 h) resulted in production of 85.19 U/ml xylanase. Taking the RSM optimized parameters in shake-flask scale into consideration; xylanase production was scaled up to bioreactor system with a working volume of 1.5 l. The peak of enzyme production was achieved after 126 h incubation that has previously been determined by RSM studies at shake flask level. Furthermore, the optimum levels of agitation and aeration in bioreactor system was found as 200 rpm and 1.5 vvm. Maximum enzyme production was close to 85 kU/l which could be translated into a productivity of 0.68 kU/l/h. No previous work considered the statistical optimization of xylanase production by A. pullulans on wheat bran and scale up of the bioprocess to a bioreactor system.Öğe Levan production by Zymomonas mobilis in batch and continuous fermentation systems(Elsevier Sci Ltd, 2014) Silbir, Selim; Dagbagli, Seval; Yegin, Sirma; Baysal, Taner; Goksungur, YektaLevan production in batch and continuous fermentation systems by Zymomonas mobilis B-14023 was investigated. The culture medium used in both of the fermentation systems contained sucrose and various organic nitrogen sources. Maximum concentration of levan was produced with yeast extract among the nitrogen sources tested. Response surface methodology was used to investigate the effects of three factors on the concentration of levan in batch cultures of Z. mobilis. Maximum levan concentration was 40.2 g/L and this concentration was reached at the optimum levels of process variables, which were 299.1 g/L initial substrate concentration, 42.3 h incubation time, and initial pH 6.0. Continuous fermentation experiments were done in packed bed bioreactor using Ca-alginate immobilized Z. mobilis cells. The highest levan concentration (31.8 +/- 0.21 g/L) was obtained at a dilution rate of 0.14 h(-1) while maximum volumetric productivity (6.556 g/(Lh)) was obtained at a dilution rate of 0.22 h(-1). Increasing the dilution rate resulted in decreased levan and increased residual sugar concentrations. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Levansucrase production by Zymomonas mobilis: Optimization of process parameters and fructooligosaccharide production(Wiley, 2017) Erdal, Ozlem; Kaplan-Turkoz, Burcu; Tastan, Ozge; Goksungur, YektaThis article investigates the production and optimization of levansucrase using synthetic medium by Zymomonas mobilis NRRL B-14023. Response surface methodology was used to investigate the effects of three different fermentation parameters on levansucrase enzyme production. Maximum levansucrase activity of 13.3 mu mol glucose/min was obtained at the optimum levels of process variables (pH 4.90, initial sucrose concentration 159.01 g/L and fermentation temperature 30.3 degrees C). Response surface methodology was found to be useful in optimizing and determining the interactions among process variables. The purity of levansucrase used in enzyme assays were analyzed by SDS-PAGE and a dominant protein band of size around 47 kDa was obtained. The sequence of the produced enzyme was determined by peptide mass fingerprinting. The presence of kestose in the reaction mixture showed that Z. mobilis levansucrase can produce fructooligosaccharides. This study fulfills the lack of mathematical and statistical approaches in optimizing the levansucrase production by Z. mobilis. Practical applicationsLevansucrases are responsible for the production of valuable fructans; fructooligosaccharides (FOS) and levan. Fructooligosaccharides are sugar polymers three times less sweet than sucrose and naturally present in some foods. FOS have important promising use in the food industry due to their properties such as solubility in water, stability during storage, low calorie value, and prebiotic effects. In this research, the production of microbial levansucrase was optimized for potential industrial applications by response surface methodology. Future studies will focus on conversion of intrinsic sucrose of foods to FOS using levansucrase.Öğe Natural Red Pigment Production by Monascus Purpureus in Submerged Fermentation Systems Using a Food Industry Waste: Brewer's Spent Grain(Mdpi, 2019) Silbir, Selim; Goksungur, YektaThis paper studies the production of natural red pigments by Monascus purpureus CMU001 in the submerged fermentation system using a brewery waste hydrolysate, brewer's spent grain (BSG). The chemical, structural and elemental characterization of the BSG was performed with Van-Soest method, Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), respectively. The lignocellulosic structure of BSG was hydrolyzed with a dilute sulfuric acid solution (2% (w/v)) followed by detoxification with Ca(OH)(2). Maximum red pigment production (22.25 UA(500)) was achieved with the following conditions: 350 rpm shake speed, 50 mL fermentation volume, initial pH of 6.5, inoculation ratio of 2% (v/v), and monosodium glutamate (MSG) as the most effective nitrogen source. Plackett-Burman design was used to assess the significance of the fermentation medium components, and MSG and ZnSO(4)7H(2)O were found to be the significant medium variables. This study is the first study showing the compatibility of BSG hydrolysate to red pigment production by Monascus purpureus in a submerged fermentation system.Öğe Optimization of 4,6-? and 4,3-?-Glucanotransferase Production in Lactococcus lactis and Determination of Their Effects on Some Quality Characteristics of Bakery Products(Mdpi, 2024) Nicin, Ramazan Tolga; Zehir-Senturk, Duygu; Ozkan, Busenur; Goksungur, Yekta; Simsek, OmerIn this study, the production of 4,6-alpha (4,6-alpha-GTase) and 4,3-alpha-glucanotransferase (4,3-alpha-GTase), expressed previously in Lactococcus lactis, was optimized and these enzymes were used to investigate glycemic index reduction and staling delay in bakery products. HP-SEC analysis showed that the relevant enzymes were able to produce oligosaccharides from potato starch or malto-oligosaccharides. Response Surface Methodology (RSM) was used to optimize enzyme synthesis and the highest enzyme activities of 15.63 +/- 1.65 and 19.01 +/- 1.75 U/mL were obtained at 1% glucose, pH 6, and 30 degrees C for 4,6-alpha-GTase and 4,3-alpha-GTase enzymes, respectively. SEM analysis showed that both enzymes reduced the size of the starch granules. These enzymes were purified by ultrafiltration and used to produce bread and bun at an enzyme activity of 4 U/g, resulting in a decrease in the specific volume of the bread. It was found that the estimated glycemic index (eGI) of bread formulated with 4,6-alpha-GTase decreased by 18.01%, and the eGI of bread prepared with 4,3-alpha-GTase decreased by 13.61%, indicating a potential delay in staling. No significant differences were observed in the sensory properties of the bakery products. This is the first study showing that 4,6-alpha-GTase and 4,3-alpha-GTase enzymes have potential in increasing health benefits and improving technological aspects regarding bakery products.Öğe Optimization of beta-Galactosidase Production in Stirred Tank Bioreactor Using Kluyveromyces lactis NRRL Y-8279(Korean Society Food Science & Technology-Kosfost, 2009) Dagbagli, Seval; Goksungur, YektaThis paper investigates the production and optimization of beta-galactosidase enzyme using synthetic medium by Kluyveromyces lactis NRRL Y-8279 in stirred tank bioreactor. Response surface methodology was used to investigate the effects of fermentation parameters on P-galactosidase enzyme production. Maximum specific enzyme activity of 4,622.7 U/g was obtained at the optimum levels of process variables (aeration rate 2.21 vvm, agitation speed 173.4 rpm, initial sugar concentration 33.8 g/L, incubation time 24.0 hr). The optimum temperature and pH of the P-galactosidase enzyme produced under optimized conditions were 37 degrees C and pH 7.0, respectively. The enzyme was stable over a pH range of 6.0-7.5 and a temperature range of 25-37 degrees C. The K-m and V-max values for O-nitrophenol-beta-D-galactopyranoside (ONPG) were 1.20 mM and 1,000 mu mol/min.mg protein, respectively. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in beta-galactosidase enzyme production. Hence, this study fulfills the lack of using mathematical and statistical techniques in optimizing beta-galactosidase enzyme production in stirred tank bioreactor.Öğe Optimization of beta-Galactosidase Production in Stirred Tank Bioreactor Using Kluyveromyces lactis NRRL Y-8279(Korean Society Food Science & Technology-Kosfost, 2009) Dagbagli, Seval; Goksungur, YektaThis paper investigates the production and optimization of beta-galactosidase enzyme using synthetic medium by Kluyveromyces lactis NRRL Y-8279 in stirred tank bioreactor. Response surface methodology was used to investigate the effects of fermentation parameters on P-galactosidase enzyme production. Maximum specific enzyme activity of 4,622.7 U/g was obtained at the optimum levels of process variables (aeration rate 2.21 vvm, agitation speed 173.4 rpm, initial sugar concentration 33.8 g/L, incubation time 24.0 hr). The optimum temperature and pH of the P-galactosidase enzyme produced under optimized conditions were 37 degrees C and pH 7.0, respectively. The enzyme was stable over a pH range of 6.0-7.5 and a temperature range of 25-37 degrees C. The K-m and V-max values for O-nitrophenol-beta-D-galactopyranoside (ONPG) were 1.20 mM and 1,000 mu mol/min.mg protein, respectively. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in beta-galactosidase enzyme production. Hence, this study fulfills the lack of using mathematical and statistical techniques in optimizing beta-galactosidase enzyme production in stirred tank bioreactor.Öğe Optimization of beta-galactosidase production using Kluyveromyces lactis NRRL Y-8279 by response surface methodology(Univ Catolica De Valparaiso, 2008) Dagbagli, Seval; Goksungur, YektaThis paper investigates the production and optimization of beta-galactosidase enzyme using synthetic medium by Kluyveromyces lactis NRRL Y-8279 in shake flask cultures. Among the different cell disintegration methods used, the highest specific activity was obtained when the cells were permeabilized using isoamyl alcohol. Response surface methodology was used to investigate the effects of four fermentation parameters (agitation speed, pH, initial substrate concentration and incubation time) on beta-galactosidase enzyme production. Results of the statistical analysis showed that the fit of the model was good in all cases. Maximum specific enzyme activity of 4218.4 U g(-1) was obtained at the optimum levels of process variables (pH 7.35, agitation speed 179.2 rpm, initial sugar concentration 24.9 g l(-1) and incubation time 50.9 hrs). The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in beta-galactosidase enzyme production.Öğe Optimization of pullulan production from hydrolysed potato starch waste by response surface methodology(Elsevier Sci Ltd, 2011) Goksungur, Yekta; Uzunogullari, Purlen; Dagbagli, SevalThe production of pullulan from hydrolysed potato starch waste by Aureobasidium pullulans P56 was investigated. The liquefaction of potato starch was done by Ca-alginate immobilized amyloglucosidase and pullulanase enzymes in a packed bed bioreactor. Various organic nitrogen sources were tested and none of the nitrogen sources gave pullulan concentrations as high as that obtained with yeast extract. Response surface methodology was used to investigate the effects of three factors (incubation time, initial substrate concentration and initial pH) on the concentration of pullulan in batch cultures of A. pullulans. No previous work has used statistical analysis on the optimization of process parameters in pullulan production from hydrolysed potato starch waste. Maximum pullulan concentration of 19.2 g/l was obtained at the optimum levels of process variables (incubation time 111.8 h, initial substrate concentration 79.4 g/l, initial pH 7.26). The optimization led to a 20% increase in pullulan concentration. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Production of extracellular aspartic protease in submerged fermentation with Mucor mucedo DSM 809(Academic Journals, 2010) Yegin, Sirma; Fernandez-Lahore, Marcelo; Guvenc, Ulgar; Goksungur, YektaFungal milk-clotting enzymes have gained value as bovine Chymosin substitutes in the cheese industry. In this work, the effects of culture conditions on the production of extracellular milk clotting enzymes from Mucor mucedo DSM 809 in submerged fermentation were studied. The maximum activity was observed after 48 h of cultivation at 24 degrees C in Erlenmeyer flasks. The optimized initial pH and shaking speed for enzyme production were 4.5 and 220 rpm, respectively. Glucose at a concentration of 1% (w/ v) was the best carbon source for the production of enzyme among the carbohydrates examined (glucose, fructose, lactose, maltodextrin). On the other hand casein at a concentration of 0.5% (w/v) was the selected nitrogen source in the media formulation. Under optimized conditions enzyme levels reached 130 SU per ml fermentation broth. The inoculum type and size has also affected biomass production and the biosynthesis of the enzyme. The preferred method was the inoculation of the culture media with spores at a total load of 6x10(5) spores per flask.Öğe UTILIZATION OF RESIDUAL BEER FOR RED PIGMENT PRODUCTION BY MONASCUS PURPUREUS IN SUBMERGED FERMENTATION(Parlar Scientific Publications (P S P), 2020) Atalay, Pinar; Sargin, Sayit; Goksungur, YektaThis paper describes the production of red pigment by Monascus purpureus CMU001 in submerged fermentation system using residual beer as an inexpensive substrate. Alcohol and CO2 removed residual beer supplemented with 7.5 g/l of monosodium glutamate was used as the fermentation medium. Shaking speed and medium volume was found to affect red pigment synthesis by M.purpureus. Maximum red pigment production of 18.54 UA(510nm) was obtained with 200 rpm shaking speed, 50 ml of the fermentation medium, initial pH of 7.0, inoculation ratio of 2% (v/v). Several nitrogen sources were screened, and the highest pigment synthesis was obtained with monosodium glutamate. Promising results were obtained with corn steep liquor and yeast extract when used as the nitrogen source in pigment production. the optimum monosodium glutamate concentration was found to be 7.5 g/L. Kinetics of pigment and biomass formation was determined under the optimized fermentation conditions over a fermentation period of 8 days. This is the first article that evaluates residual beer for pigment synthesis using M.purpureus in the submerged fermentation system.Öğe Utilization of Whey for Red Pigment Production by Monascus purpureus in Submerged Fermentation(Mdpi, 2021) Mehri, Dilara; Perendeci, N. Altinay; Goksungur, YektaVarious biotechnological approaches have been employed to convert food waste into value-added bioproducts through fermentation processes. Whey, a major waste generated by dairy industries, is considered an important environmental pollutant due to its massive production and high organic content. The purpose of this study is to investigate the effect of different fermentation parameters in simultaneous hydrolysis and fermentation (SHF) of whey for pigment production with Monascus purpureus. The submerged culture fermentation parameters optimized were type and pretreatment of whey, pH, inoculation ratio, substrate concentration and monosodium glutamate (MSG) concentration. Demineralized (DM), deproteinized (DP), and raw whey (W) powders were used as a substrate for pigment production by simultaneous hydrolysis and fermentation (SHF). The maximum red pigment production was obtained as 38.4 UA(510 nm) (absorbance units) at the optimized condition of SHF. Optimal conditions of SHF were 2% (v/v) inoculation ratio, 75 g/L of lactose as carbon source, 25 g/L of MSG as nitrogen source, and fermentation medium pH of 7.0. The specific growth rate of M. purpureus on whey and the maximum pigment production yield values were 0.023 h(-1) and 4.55 UAd(-1), respectively. This study is the first in the literature to show that DM whey is a sustainable substrate in the fermentation process of the M. purpureus red pigment.