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Fikret Kargi - One of the best experts on this subject based on the ideXlab platform.
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Effects of starch loading rate on performance of combined Fed-Batch fermentation of ground wheat for bio-hydrogen production
International Journal of Hydrogen Energy, 2010Co-Authors: Serpil Ozmihci, Fikret KargiAbstract:Abstract Ground wheat powder solution (10 g L −1 ) was subjected to combined dark and light fermentations for bio-hydrogen production by Fed-Batch Operation. A mixture of heat treated anaerobic sludge (AN) and Rhodobacter sphaeroides -NRRL (RS-NRRL) were used as the mixed culture of dark and light fermentation bacteria with an initial dark/light biomass ratio of 1/2. Effects of wheat starch loading rate on the rate and yield of bio-hydrogen formation were investigated. The highest cumulative hydrogen formation (CHF = 3460 ml), hydrogen yield (201 ml H 2 g −1 starch) and formation rate (18.1 ml h −1 ) were obtained with a starch loading rate of 80.4 mg S h −1 . Complete starch hydrolysis and glucose fermentation were achieved within 96 h of Fed-Batch Operation producing volatile fatty acids (VFA) and H 2 . Fermentation of VFAs by photo-fermentation for bio-hydrogen production was most effective at starch loading rate of 80.4 mg S h −1 . Hydrogen formation by combined fermentation took place by a fast dark fermentation followed by a rather slow light fermentation after a lag period.
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Effects of dark/light bacteria ratio on bio-hydrogen production by combined Fed-Batch fermentation of ground wheat starch
Biomass and Bioenergy, 2010Co-Authors: Fikret Kargi, Serpil OzmihciAbstract:Bio-hydrogen production by combined dark and light fermentation of ground wheat starch was investigated using Fed-Batch Operation. Serum bottles containing heat-treated anaerobic sludge and a mixture of Rhodobacter sp. was fed with a medium containing 20gdm -3 wheat powder (WP) at a constant flow rate. The system was operated at different initial dark/light biomass ratios (D/L). The optimum D/L ratio was 1/2 yielding the highest cumulative hydrogen (1548cm 3), yield (65.2cm 3g -1 starch), and specific hydrogen production rate (5.18cm 3g -1h -1). Light fermentation alone yielded higher hydrogen production than dark fermentation due to fermentation of volatile fatty acids (VFAs) to H 2 and CO 2. The lowest hydrogen formation was obtained with D/L ratio of 1/1 due to accumulation of VFAs in the medium. © 2010 Elsevier Ltd.
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Dark fermentation of ground wheat starch for bio-hydrogen production by Fed-Batch Operation
International Journal of Hydrogen Energy, 2009Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Abstract Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in Fed-Batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33 mL h−1 (200 mL d−1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30 g L−1. The residual starch (substrate) concentration in the fermenter decreased with Operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600 mL), hydrogen yield (465 mL H2 g−1 starch or 3.1 mol H2 mol−1 glucose) and hydrogen production rate (864 mL H2 d−1) were obtained after 4 days of Fed-Batch Operation with the 20 g L−1 feed WP concentration corresponding to a WP loading rate of 4 g WP d−1. Low feed WP concentrations (10 g L−1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30 g L−1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production.
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Dark fermentation of ground wheat starch for bio-hydrogen production by Fed-Batch Operation
International Journal of Hydrogen Energy, 2009Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in Fed-Batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33 mL h-1 (200 mL d-1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30 g L-1. The residual starch (substrate) concentration in the fermenter decreased with Operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600 mL), hydrogen yield (465 mL H2 g-1 starch or 3.1 mol H2 mol-1 glucose) and hydrogen production rate (864 mL H2 d-1) were obtained after 4 days of Fed-Batch Operation with the 20 g L-1 feed WP concentration corresponding to a WP loading rate of 4 g WP d-1. Low feed WP concentrations (10 g L-1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30 g L-1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production. © 2009 International Association for Hydrogen Energy.
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ethanol fermentation of cheese whey powder solution by repeated fed batch Operation
Enzyme and Microbial Technology, 2007Co-Authors: Serpil Ozmihci, Fikret KargiAbstract:Abstract Ethanol fermentation of cheese whey powder (CWP) solution was realized in a Fed-Batch operated fermenter using the pure culture of Kluyveromyces marxianus (DSMZ 7239) at different feed CWP concentrations varying between 51 and 408 g l −1 . Total sugar content of the feed varied between 25 and 200 g l −1 with a constant flow rate of 0.084 l h −1 . Sugar utilization, ethanol formation and biomass growth were investigated as function of the feed sugar concentration in a five-cycle repeated Fed-Batch Operation where the system reached the quasi steady-state. Variations of the growth and the product yield coefficients with the feed sugar concentration were quantified. The growth yield coefficient ( Y X / S ) decreased with increasing feed sugar concentrations. The product yield coefficient ( Y P / S ) was almost constant (0.54 ± 0.02 g EtOH g −1 S ) for sugar concentrations between 25 and 150 g l −1 , but decreased at the feed sugar concentration of 200 g l −1 due to high osmotic pressure at high sugar concentrations. The highest ethanol concentration (63 g l −1 ) and the productivity (5.3 g EtOH h −1 ) were obtained with a 125 g l −1 feed sugar concentration and sugar loading rate of 10.5 g S h −1 .
M. Yunus Pamukoglu - One of the best experts on this subject based on the ideXlab platform.
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Dark fermentation of ground wheat starch for bio-hydrogen production by Fed-Batch Operation
International Journal of Hydrogen Energy, 2009Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Abstract Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in Fed-Batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33 mL h−1 (200 mL d−1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30 g L−1. The residual starch (substrate) concentration in the fermenter decreased with Operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600 mL), hydrogen yield (465 mL H2 g−1 starch or 3.1 mol H2 mol−1 glucose) and hydrogen production rate (864 mL H2 d−1) were obtained after 4 days of Fed-Batch Operation with the 20 g L−1 feed WP concentration corresponding to a WP loading rate of 4 g WP d−1. Low feed WP concentrations (10 g L−1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30 g L−1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production.
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Dark fermentation of ground wheat starch for bio-hydrogen production by Fed-Batch Operation
International Journal of Hydrogen Energy, 2009Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in Fed-Batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33 mL h-1 (200 mL d-1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30 g L-1. The residual starch (substrate) concentration in the fermenter decreased with Operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600 mL), hydrogen yield (465 mL H2 g-1 starch or 3.1 mol H2 mol-1 glucose) and hydrogen production rate (864 mL H2 d-1) were obtained after 4 days of Fed-Batch Operation with the 20 g L-1 feed WP concentration corresponding to a WP loading rate of 4 g WP d-1. Low feed WP concentrations (10 g L-1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30 g L-1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production. © 2009 International Association for Hydrogen Energy.
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Adsorbent supplemented biological treatment of pre-treated landfill leachate by Fed-Batch Operation.
Bioresource Technology, 2004Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Abstract Biological treatment of landfill leachate usually results in low COD removals because of high chemical oxygen demand (COD), high ammonium-N content and presence of toxic compounds. Coagulation–flocculation with lime addition and air stripping of ammonia were used as pre-treatment in this study in order to improve biological treatability of the leachate. Pre-treated leachate was subjected to adsorbent supplemented biological treatment in an aeration tank operated in Fed-Batch mode. COD and NH 4 -N removal performances of powdered activated carbon (PAC) and powdered zeolite (PZ) were compared during biological treatment. Adsorbent concentrations varied between 0 and 5 g l −1 . Percent COD and ammonium-N removals increased with increasing adsorbent concentrations. Percent COD removals with PAC addition were significantly higher than those obtained with the zeolite. However, zeolite performed better than the PAC in ammonium-N removal from the leachate. Nearly 87% and 77% COD removals were achieved with PAC and zeolite concentrations of 2 g l −1 , respectively. Ammonium-N removals were 30% and 40% with PAC and zeolite concentrations of 5 g l −1 , respectively at the end of 30 h of Fed-Batch Operation.
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Aerobic biological treatment of pre-treated landfill leachate by Fed-Batch Operation
Enzyme and Microbial Technology, 2003Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Abstract Landfill leachate obtained from the solid waste landfill area contained high chemical oxygen demand (COD) and ammonium ions which resulted in low COD and ammonium removals by direct biological treatment. COD and ammonium ion contents of the leachate were reduced to reasonable levels by chemical precipitation with lime and air stripping of ammonia. The pre-treated leachate was subjected to aerobic biological treatment in an aeration tank by Fed-Batch Operation. The effects of the feed wastewater COD content and flow rate on COD and ammonium ions removal were investigated. Nearly 76% COD and 23% NH 4 -N removals were obtained after 30 h of Operation with a flow rate of 0.21 l h −1 and the feed COD content of 7000 mg COD l −1 . COD removal efficiency decreased with increasing COD loading rates. A kinetic model for COD removal was developed and the kinetic constants were determined by using the experimental data.
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Simultaneous adsorption and biological treatment of pre-treated landfill leachate by Fed-Batch Operation
Process Biochemistry, 2003Co-Authors: Fikret Kargi, M. Yunus PamukogluAbstract:Abstract Due to high chemical oxygen demand (COD), ammonium–N content and presence of toxic compounds such as heavy metals, direct biological treatment of landfill leachate results in low removal efficiencies. In order to improve biological treatability of the leachate, coagulation–flocculation and air stripping of ammonia were used as pre-treatment. Pre-treated leachate was treated biologically using an aeration tank operated in Fed-Batch mode in the absence and presence of powdered activated carbon (PAC) as adsorbent. PAC addition improved COD removal significantly especially at concentrations above 0.5 g l −1 . However, improvements in COD removals were marginal for PAC concentrations above 2 g l −1 . Nearly 86% COD removal was achieved with 2 g l −1 PAC added biological treatment whereas, COD removals by only biological oxidation and only PAC adsorption were nearly 74 and 38%, respectively at the end of 30 h of Fed-Batch Operation. An empirical equation was developed to describe the contribution of adsorption over biological treatment as a function of PAC concentration.
Tai Hyun Park - One of the best experts on this subject based on the ideXlab platform.
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Hydrogen production from formic acid in pH-stat Fed-Batch Operation for direct supply to fuel cell.
Bioresource technology, 2009Co-Authors: Jong-hwan Shin, Jong Hyun Yoon, Tai Hyun ParkAbstract:Enterobacter asburiae SNU-1 harvested after cultivation was used as a whole cell biocatalyst, for the production of hydrogen. Formic acid was efficiently converted to hydrogen using the harvested cells with an initial hydrogen production rate and total hydrogen production of 491 ml/l/h and 6668 ml/l, respectively, when 1 g/l of whole cell enzyme was used. Moreover, new pH-stat Fed-Batch Operation was conducted, and total hydrogen production was 1.4 times higher than that of batch Operation. For practical application, bio-hydrogen produced from formic acid using harvested cells was directly applied to PEMFC for power generation.
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Importance of specific growth rate for subtilisin expression in Fed-Batch cultivation of Bacillus subtilis spoIIG mutant
Enzyme and Microbial Technology, 2002Co-Authors: Jeong Seok Oh, Tai Hyun ParkAbstract:Abstract A feeding strategy was developed for controlling the specific growth rate in a Bacillus subtilis Fed-Batch Operation, and the importance of the specific growth rate was investigated for subtilisin expression. The ratio of the glucose and peptone concentrations in the feeding medium was critical in controlling the specific growth rate, and the appropriate ratio was found to be 1:2. The specific growth rate was well controlled in Fed-Batch Operations including an exponential feeding of a 200 g/liter glucose and 400 g/liter peptone solution. Controlling the value of the specific growth rate had a significant effect on the subtilisin expression, even though the subtilisin expression was only enhanced after the feeding ended. This would appear to be due to cell components, such as sigma factors, produced in the growth phase that influenced the aprE gene expression. The optimal specific growth rate for the maximum expression rate and longest production period was 0.35 h−1.
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fed batch Operation of recombinant escherichia coli containing trp promoter with controlled specific growth rate
Biotechnology and Bioengineering, 1994Co-Authors: Sung Kwan Yoon, Whan Koo Kang, Tai Hyun ParkAbstract:A feb-batch Operation for the production of bovine somatotropin (bST) under the control of tryptophan promoter in Escherichia coli was investigated. The plasmid used contains a two-cistron system and altered codon usage for higher expression of bST. Specific growth rate is an important parameter in the fermentation, because it affects the production of growth-inhibitory organic acids and the expression of recombinant protein. The feeding rate was adjusted to keep the specific growth rate constant in this study. The variable growth yield expressed as a function of time was used for the calculation of the feeding rate. The growth yield decreases during the fermentation as product expression is induced. The specific growth rate was well controlled; however, intracellular bST concentration decreased at high cell concentrations. This is considered to be due to degradation by proteases. The decrease was prevented by an exponential feeding of the yeast extract as an organic nitrogen source. © 1994 John Wiley & Sons, Inc.
Serpil Ozmihci - One of the best experts on this subject based on the ideXlab platform.
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Effects of starch loading rate on performance of combined Fed-Batch fermentation of ground wheat for bio-hydrogen production
International Journal of Hydrogen Energy, 2010Co-Authors: Serpil Ozmihci, Fikret KargiAbstract:Abstract Ground wheat powder solution (10 g L −1 ) was subjected to combined dark and light fermentations for bio-hydrogen production by Fed-Batch Operation. A mixture of heat treated anaerobic sludge (AN) and Rhodobacter sphaeroides -NRRL (RS-NRRL) were used as the mixed culture of dark and light fermentation bacteria with an initial dark/light biomass ratio of 1/2. Effects of wheat starch loading rate on the rate and yield of bio-hydrogen formation were investigated. The highest cumulative hydrogen formation (CHF = 3460 ml), hydrogen yield (201 ml H 2 g −1 starch) and formation rate (18.1 ml h −1 ) were obtained with a starch loading rate of 80.4 mg S h −1 . Complete starch hydrolysis and glucose fermentation were achieved within 96 h of Fed-Batch Operation producing volatile fatty acids (VFA) and H 2 . Fermentation of VFAs by photo-fermentation for bio-hydrogen production was most effective at starch loading rate of 80.4 mg S h −1 . Hydrogen formation by combined fermentation took place by a fast dark fermentation followed by a rather slow light fermentation after a lag period.
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Effects of dark/light bacteria ratio on bio-hydrogen production by combined Fed-Batch fermentation of ground wheat starch
Biomass and Bioenergy, 2010Co-Authors: Fikret Kargi, Serpil OzmihciAbstract:Bio-hydrogen production by combined dark and light fermentation of ground wheat starch was investigated using Fed-Batch Operation. Serum bottles containing heat-treated anaerobic sludge and a mixture of Rhodobacter sp. was fed with a medium containing 20gdm -3 wheat powder (WP) at a constant flow rate. The system was operated at different initial dark/light biomass ratios (D/L). The optimum D/L ratio was 1/2 yielding the highest cumulative hydrogen (1548cm 3), yield (65.2cm 3g -1 starch), and specific hydrogen production rate (5.18cm 3g -1h -1). Light fermentation alone yielded higher hydrogen production than dark fermentation due to fermentation of volatile fatty acids (VFAs) to H 2 and CO 2. The lowest hydrogen formation was obtained with D/L ratio of 1/1 due to accumulation of VFAs in the medium. © 2010 Elsevier Ltd.
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ethanol fermentation of cheese whey powder solution by repeated fed batch Operation
Enzyme and Microbial Technology, 2007Co-Authors: Serpil Ozmihci, Fikret KargiAbstract:Abstract Ethanol fermentation of cheese whey powder (CWP) solution was realized in a Fed-Batch operated fermenter using the pure culture of Kluyveromyces marxianus (DSMZ 7239) at different feed CWP concentrations varying between 51 and 408 g l −1 . Total sugar content of the feed varied between 25 and 200 g l −1 with a constant flow rate of 0.084 l h −1 . Sugar utilization, ethanol formation and biomass growth were investigated as function of the feed sugar concentration in a five-cycle repeated Fed-Batch Operation where the system reached the quasi steady-state. Variations of the growth and the product yield coefficients with the feed sugar concentration were quantified. The growth yield coefficient ( Y X / S ) decreased with increasing feed sugar concentrations. The product yield coefficient ( Y P / S ) was almost constant (0.54 ± 0.02 g EtOH g −1 S ) for sugar concentrations between 25 and 150 g l −1 , but decreased at the feed sugar concentration of 200 g l −1 due to high osmotic pressure at high sugar concentrations. The highest ethanol concentration (63 g l −1 ) and the productivity (5.3 g EtOH h −1 ) were obtained with a 125 g l −1 feed sugar concentration and sugar loading rate of 10.5 g S h −1 .
Tsu-yuan Shih - One of the best experts on this subject based on the ideXlab platform.
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Coenzyme Q_10 production by Rhodobacter sphaeroides in stirred tank and in airlift bioreactor
Bioprocess and Biosystems Engineering, 2009Co-Authors: Tsu-yuan ShihAbstract:A higher Coenzyme Q_10 (CoQ_10) concentration of 25.04 mg/l was found in airlift bioreactor than the value of 18.11 mg/l obtained in stirred tank under the aerobic-dark cultivation of Rhodobacter sphaeroides . Aeration rate didn’t show obvious impact to CoQ_10 production in airlift bioreactor. The Fed-Batch Operation in airlift bioreactor could increase the biomass concentration and led to the maximum CoQ_10 concentration of 33.91 mg/l measured, but a lower CoQ_10 cell content (3.5 mg CoQ_10/DCW) was observed in the Fed-Batch Operation as compared to the batch Operation. To enhance the CoQ_10 content, an aeration-change strategy was proposed in the Fed-Batch Operation of airlift bioreactor. This strategy led to the maximum CoQ_10 concentration of 45.65 mg/l, a 35% increase as compared to the simple Fed-Batch Operation. The results of this study suggested that a Fed-Batch Operation in airlift bioreactor accompanying aeration-change could be suitable for CoQ_10 production.
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Coenzyme Q10 production by Rhodobacter sphaeroides in stirred tank and in airlift bioreactor
Bioprocess and Biosystems Engineering, 2009Co-Authors: Tsu-yuan ShihAbstract:A higher Coenzyme Q10 (CoQ10) concentration of 25.04 mg/l was found in airlift bioreactor than the value of 18.11 mg/l obtained in stirred tank under the aerobic-dark cultivation of Rhodobacter sphaeroides. Aeration rate didn’t show obvious impact to CoQ10 production in airlift bioreactor. The Fed-Batch Operation in airlift bioreactor could increase the biomass concentration and led to the maximum CoQ10 concentration of 33.91 mg/l measured, but a lower CoQ10 cell content (3.5 mg CoQ10/DCW) was observed in the Fed-Batch Operation as compared to the batch Operation. To enhance the CoQ10 content, an aeration-change strategy was proposed in the Fed-Batch Operation of airlift bioreactor. This strategy led to the maximum CoQ10 concentration of 45.65 mg/l, a 35% increase as compared to the simple Fed-Batch Operation. The results of this study suggested that a Fed-Batch Operation in airlift bioreactor accompanying aeration-change could be suitable for CoQ10 production.