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Öğe Adsorption Equilibrium and Dynamics of Lactase/Cm-Sephadex System(Chapman Hall Ltd, 1995) Harsa, S; Goksungur, Y; Guvenc, UPartitioning behaviour and adsorption isotherms of lactase/CM-Sephadex system at equilibrium were investigated together with the adsorption kinetics in this study. Maximum adsorption was obtained at the pH values between 5.5-6.0. Adsorption isotherm was a close fit to the Langmuir model.Öğe Batch and continuous production of lactic acid from beet molasses by Lactobacillus delbrueckii IFO 3202(John Wiley & Sons Ltd, 1997) Goksungur, Y; Guvenc, UProcess variables were optimized for the production of lactic acid from pretreated beet molasses by Lacrobacillus delbrueckii IFO 3202 for batch and continuous fermentations. In the batch fermentation, maximum yields (95. 4% conversion, 77.1% effective) and maximum lactic acid volumetric productivity (483 g dm(-3) h(-1)) was achieved at 45 degrees C, pH 6.0, 78.2 g dm(-3) sugar concentration with 10 g dm(-3) yeast extract. Various cheaper nitrogen sources were replaced with yeast extract on equal nitrogen bases in batch fermentation. Of all the nitrogen sources tested, yeast extract yielded the highest and malt sprouts yielded the second highest level of lactic acid. In the continuous fermentation, maximum lactic acid (4.15%) was obtained at a dilution rate of 0.1 h(-1). Maximum volumetric lactic acid productivity (11.20 g dm(-3) h(-1)) occurred at D = 0.5 h(-1) dilution rate.Öğe Effect of potassium sorbate and sodium benzoate on microbial population and fermentation of black olives(John Wiley & Sons Ltd, 1999) Turantas, F; Goksungur, Y; Dincer, AH; Unluturk, A; Guvenc, U; Zorlu, NBlack olive fermentation characteristics and diffusion of preservatives into olives were evaluated in brines containing 500ppm potassium sorbate, 1000ppm sodium benzoate, 500ppm sodium benzoate + 250ppm potassium sorbate and no preservative (control). Changes in brine pH, acidity and microbial population (lactic acid bacteria, yeasts, moulds) were followed during fermentation and storage. Results indicated that K-sorbate when used at 500ppm concentration in black olive fermentation had a slight stimulatory effect on the growth of lactic acid bacteria. The yeast counts of brines containing 500 ppm K-sorbate and 1000ppm Na-benzoate were lower than for the brine containing 250 ppm K-sorbate + 500ppm Na-benzoate and for the control with no preservative, while mould growth was completely inhibited in all treatments during fermentation. Mould counts stayed below the detection Limit (<10 cfu g(-1)) during 214 days of vacuum-packaged storage. Yeast counts showed a progressive decline within 28 days of storage and then stayed relatively constant in all treatments thereafter. The level of yeast population was higher in the control sample than in the sample containing both preservatives during storage. The diffusion of Na-benzoate and K-sorbate into the olives after equilibrium was 64% and 80% during fermentation respectively. (C) 1999 Society of Chemical Industry.Öğe Optimization of lactic acid production from whey by L casei NRRL B-441 immobilized in chitosan stabilized Ca-alginate beads(Wiley, 2005) Goksungur, Y; Gunduz, M; Harsa, SThe production of lactic acid from whey by Lactobacillus casei NRRL B-441 immobilized in chitosan-stabilized Ca-alginate beads was investigated. Higher lactic acid production and lower cell leakage were observed with alginate-chitosan beads compared with Ca-alginate beads. The highest lactic acid concentration (131.2 g dm(-3)) was obtained with cells entrapped in 1.3-1.7 mm alginate-chitosan beads prepared from 2% (w/v) Na-alginate. The gel beads produced lactic acid for five consecutive batch fermentations without marked activity loss and deformation. Response surface methodology was used to investigate the effects of three fermentation parameters (initial sugar, yeast extract and calcium carbonate concentrations) on the concentration of lactic acid. Results of the statistical analysis showed that the fit of the model was good in all cases. Initial sugar, yeast extract and calcium carbonate concentrations had a strong linear effect on lactic acid production. The maximum lactic acid concentration of 136.3 g dm(-3) was obtained at the optimum concentrations of process variables (initial sugar 147.35 g dm(-3), yeast extract 28.81 g dm(-3), CaCO3 97.55 g dm(-3)). These values were obtained by fitting of the experimental data to the model equation. The response surface methodology was found to be useful in optimizing and determining the interactions among process variables in lactic acid production using alginate-chitosan-immobilized cells. (c) 2005 Society of Chemical Industry.Öğe Optimization of pullulan production from synthetic medium by Aureobsidium pullulans in a stirred tank reactor by response surface methodology(Wiley, 2005) Goksungur, Y; Dagbagli, S; Ucan, A; Guvenc, UThe production of pullulan from synthetic medium by Aureobasidium pullulans P56 in a stirred tank fermenter was investigated. The kinetics of polysaccharide, pullulan and biomass production was determined. Response surface methodology was used to investigate the effects of three factors (initial sugar concentration, aeration rate and agitation speed) on the concentration of pullulan in batch cultures of A pullulans. In the experiments, the range of values used for the three variables described were; 30-70 g dm(-3) initial sugar concentration, 200-600 rpm agitation speed and 1.0-3.0 vvm aeration rate. No previous work has used statistical analysis in determining the interactions among these variables in pullulan production. Results of the statistical analysis showed that the fit of the model was good in all cases. Aeration rate, agitation speed and sugar concentration 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 with the exception that the interaction between agitation speed and aeration rate was insignificant (P > 0.05). Maximum pullulan concentration of 17.2 g dm(-3) was obtained at the optimum levels of process variables (initial sugar concentration 51.4 g dm(-3), aeration rate 2.36 vvm, agitation speed 345.3 rpm). These values were obtained by fitting of the experimental data to the model equation. Scanning electron microscope (SEM) photographs of polysaccharide particles containing different concentrations of pullulan were also taken to observe the morphological differences of the samples. (c) 2005 Society of Chemical Industry.Öğe Optimization of the production of beta-carotene from molasses by Blakeslea trispora: a statistical approach(Wiley, 2002) Goksungur, Y; Mantzouridou, F; Roukas, TThe effect of pretreatment of molasses, nitrogen sources, natural oils, fatty acids, antioxidant, precursors, and mixtures of the above substances on beta-carotene production by Blakeslea trispora in shake flask culture was investigated. Also, a central composite design was employed to determine the maximum beta-carotene concentration at optimum values for the process variables (linoleic acid, kerosene, antioxidant). The highest concentration of the carotenoid pigment was obtained in molasses solution treated with invertase. Corn steep liquor and yeast extract at concentrations of 5.0% and 0.5% (w/v), respectively, increased slightly the concentration of beta-carotene, while the natural oils, fatty acids, and precursors (except kerosene) did not improve the production of pigment when they were added separately to the medium. On the other hand, the mixture of linoleic acid, kerosene and antioxidant increased significantly the concentration of beta-carotene. The fit of the model was found to be good. Linoleic acid, kerosene and antioxidant had a strong linear effect on beta-carotene concentration. The concentration of beta-carotene was significantly affected by linoleic acid-antioxidant and kerosene-antioxidant interactions as well as by the negative quadratic effects of these variables. The interaction between linoleic acid-kerosene had no significant linear effect. Maximum P-carotene concentration (790.0 mg dm(-3)) was obtained in culture grown in molasses solution supplemented with linoleic acid (30.74 g dm(-3)), kerosene (27.79 g dm(-3)) and antioxidant (10.22 g dm(-3)). (C) 2002 Society of Chemical Industry.Öğe Production of antimicrobial films by incorporation of partially purified lysozyme into biodegradable films of crude exopolysaccharides obtained from Aureobasidium pullulans fermentation(Faculty Food Technology Biotechnology, 2005) Kandemir, N; Yemenicioglu, A; Mecitoglu, I; Elmaci, ZS; Arslanoglu, A; Goksungur, Y; Baysal, TAntimicrobial films were produced by incorporating partially purified lysozyme into films of crude exopolysaccharides (59 % pullulan) obtained from Aureobasidium pullulans fermentation. After film making, the films containing lysozyme at 100, 260, 520 and 780 mu g/cm(2) showed 23 to 70 % of their expected enzyme activities. The highest recovery of enzyme activity (65-70 %) after the film making was obtained in films prepared by incorporating lysozyme at 260 mu g/cm(2) (1409 U/cm(2)). The incorporation of disodium EDTA(.)2H(2)O and sucrose did not affect the initial lysozyme activity of the films significantly. With or without the presence of disodium EDTA(.)2H(2)O at 52 or 520 mu g/cm(2), lysozyme activity showed sufficient stability in the films during 21 days of cold storage. However, the presence of sucrose at 10 mg/cm(2) in the films caused the destabilization of part of enzyme activity (almost 35 %) at the end of storage. The combinational incorporation of lysozyme at 780 pg/cm(2) (4227 U/cm(2)) and disodium EDTA(.)2H(2)O at 520 mu g/cm(2) gave antimicrobial films effective on Escherichia coli. However, in the studied lysozyme concentration range the films did not show any antimicrobial activity against Lactobacillus plantarum. This study clearly showed that the partially purified lysozyme and crude exopolysaccharides from Aureobasidium pullulans may be used to obtain antimicrobial films to increase the safety of foods.Öğe Production of beta-carotene from beet molasses by Blakeslea trispora in stirred-tank and bubble column reactors - Development of a mathematical modeling(Humana Press Inc, 2004) Goksungur, Y; Mantzouridou, F; Roukas, T; Kotzekidou, PThe effect of aeration rate and agitation speed on beta-carotene production from molasses by Blakeslea trispora in a stirred-tank fermentor and optimization of the production of the pigment in a bubble column reactor were investigated. In addition, a central composite design was employed to determine the maximum beta-carotene concentration at optimum values for the process variables (aeration rate, sugar concentration, linoleic acid, kerosene). By image analysis of the morphology of the fungus, a quantitative characterization of the hyphae and zygospores formed was obtained. The hyphae were differentiated to intact hyphae, vacuolated hyphae, evacuated cells and degenerated hyphae. An increased proportion of zygospores was correlated to high beta-carotene production. In the stirred-tank fermentor, the highest concentration of the carotenoid pigment (92.0 mg/L) was obtained at an aeration rate of 1.5 vvm and agitation speed of 60 rpm. In the bubble column reactor, the aeration rate and concentration of sugars, linoleic acid, kerosene, and antioxidant significantly affected the production of beta-carotene. In all cases, the fit of the model was found to be good. Aeration rate, sugar concentration, linoleic acid, and kerosene had a strong positive linear effect on beta-carotene concentration. Moreover, the concentration of the pigment was significantly influenced by the negative quadratic effects of the given variables and by their positive or negative interactions. Maximum beta-carotene concentration (360.2 mg/L) was obtained in culture grown in molasses solution containing 5% (w/v) sugar supplemented with linoleic acid (37.59 g/L), kerosene (39.11 g/L), and antioxidant (1.0 g/L).Öğe Production of lactic acid from beet molasses by calcium alginate immobilized Lactobacillus delbrueckii IFO 3202(John Wiley & Sons Ltd, 1999) Goksungur, Y; Guvenc, ULactic acid was produced from pretreated beet molasses by the homofermentative organism Lactobacillus delbrueckii subsp delbrueckii IFO 3202 entrapped in calcium alginate gel using batch, repeated batch and continuous fermentation systems. In batch fermentation studies successful results were obtained with 2.0-2.4 mm diameter beads prepared from 2% sodium alginate solution. The highest effective yield (82.0%) and conversion yield (90.0%) were obtained from substrate concentrations of 52.1 and 78.2 g dm(-3) respectively. The gel beads produced lactic acid for 14 consecutive batch fermentations without marked activity loss and deformation. In the continuous fermentation, the highest lactic acid (4.22%) was obtained at a dilution rate of 0.1 h(-1) while the highest productivity (13.92 g dm(-3) h(-1)) was obtained at a dilution rate of 0.4 h(-1). (C) 1999 Society of Chemical Industry.
