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Ali Demirci - One of the best experts on this subject based on the ideXlab platform.
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Application of mathematical models to ethanol fermentation in Biofilm Reactor with carob extract
Biomass Conversion and Biorefinery, 2019Co-Authors: Mustafa Germec, Kuan-chen Cheng, Ali Demirci, Mustafa Karhan, Irfan TurhanAbstract:Mathematical models not only ensure information about kinetic-metabolic nature of fermentations, but also facilitate their control and optimization. In the study, flexible ten models were evaluated and employed to describe the ethanol fermentation in a Biofilm Reactor with a carob extract medium (CEM). Findings indicated that W model well fitted the experimental data of cell growth (root mean square error (RMSE) = 0.289 g/L, mean absolute error (MAE) = 0.237 g/L, regression coefficient ( R ^ 2 ) = 0.9944, bias factor (BF) = 1.021, and accuracy factor (AF) = 1.047), ethanol production (RMSE = 1.609 g/L, MAE = 1.277 g/L, R ^ 2 = 0.9774, BF = 1.178, and AF = 1.283), and substrate consumption (RMSE = 2.493 g/L, MAE = 1.546 g/L, R ^ 2 = 0.9931, BF = 1.001 and AF = 1.053). In the prediction of kinetic parameters, W model also gave better and well-directed results compared with the other mathematical models used in the study. When an independent set of experimental data was used in the validation of mathematical models, similar validation results were obtained and W model was also successful. Consequently, W model could be used for more progress of fermentation process in Biofilm Reactor with CEM, which can serve as a universal equation.
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Ethanol production from carob extract by using Saccharomyces cerevisiae in Biofilm Reactor
2016 ASABE International Meeting, 2016Co-Authors: Mustafa Germec, Irfan Turhan, Mustafa Karhan, Ali DemirciAbstract:Abstract. Carob, widely grown in Mediterranean countries, contains several types of sugars such as 34 42% sucrose, 7-10% glucose, and 10-12% fructose. Due to the high sugar concentration, it is used for production of many value added products via fermentation such as ethanol, lactic acid, citric acid, pullulan, and mannanase. In this study, ethanol production conditions from carob extract through repeated-batch fermentation by using Saccharomycess cerevisiae in Biofilm Reactor were optimized by response surface methodology. Initial sugar concentration (4-10°Bx), agitation speed (100-200 rpm), and pH (5.0-6.0) were used as variable parameters. Results showed that initial sugar concentration had a significant effect on yield and maximum production rate. Optimum conditions were found to be 7.71°Bx, 120 rpm, and 5.18, respectively. After validation experiments ethanol concentration, yield, maximum production rate, and sugar utilization yield were determined as 24.51 g/L, 48.59%, 2.14 g/L/h, and 87.33%, respectively and fermentation time was reduced to 12 h using a Biofilm Reactor due to high biomass concentration as Biofilms. Moreover, the effect of nitrogen sources used in media and non-enriched medium were also investigated. According to results while ethanol production, yield, and maximum production rate were considerably reduced compared to optimized conditions in Biofilm Reactor, sugar utilization yield was slightly similar. Consequently, whether ethanol production from carob extract in Biofilm Reactor was victoriously performed, fermentation time was significantly decreased compared to data in the literature.
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ethanol production via repeated batch fermentation from carob pod extract by using saccharomyces cerevisiae in Biofilm Reactor
Fuel, 2015Co-Authors: Mustafa Germec, Irfan Turhan, Mustafa Karhan, Ali DemirciAbstract:Abstract In present study, repeated-batch fermentation in Biofilm Reactor was evaluated for ethanol production by using carob extract. Response surface method (RSM) was used to determine optimum initial sugar concentration, pH, and agitation in the constructed Biofilm Reactor. The optimum conditions for ethanol production in Biofilm Reactor were determined as initial sugar content of 7.71°Bx, pH of 5.18 and agitation of 120 rpm. The ethanol production (P), the yield (YP/S) and production rate (QP) were found as 24.51 g/L 48.59% and 2.14 g/L/h at the optimized conditions, respectively. The fermentation time for maximum ethanol production in carob extract was reduced to 12 h by using a Biofilm Reactor compared the published data in the literature, which was 30 and 24 h by using suspended and immobilized yeasts in a stirred tank Reactor, respectively. Furthermore, the effect of various nitrogen sources and enrichment were also evaluated and YP/S, QS and QP were significantly decreased compared to the results obtained from optimum conditions in Biofilm Reactor. Overall, results showed that a Biofilm Reactor for ethanol production from carob extract can be successfully implemented in point of reducing fermentation time, eliminate re-inoculation of the typical batch fermentation as well as increasing production yield.
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Enhanced human lysozyme production in Biofilm Reactor by Kluyveromyces lactis K7
Biochemical Engineering Journal, 2014Co-Authors: Duygu Ercan, Ali DemirciAbstract:Abstract Lysozyme is an antimicrobial compound, which has been used in pharmaceutical and food industries. Chicken egg is the commercial source of lysozyme. However, human lysozyme is more effective and safer than egg-white lysozyme. Human milk is an important source for human lysozyme, but it is not feasible to provide the needed lysozyme commercially. Biofilm Reactors provide passive immobilization of cells onto the solid support, which may lead to higher productivity. The aim was to evaluate the fermentation medium composition for enhanced human lysozyme production by Kluyveromyces lactis K7 in Biofilm Reactor with plastic composite supports. Yeast nitrogen base was selected as the best nitrogen source when compared to the yeast extract and corn steep liquor. Moreover, inhibition effect of NaCl and NH4Cl at the concentrations of 25 and 50 mM was observed. Three factors Box–Behnken response surface design was conducted and the results suggested 16.3% lactose, 1.2% casamino acid, 0.8% yeast nitrogen base as optimum medium composition for maximum human lysozyme production. Overall, the human lysozyme production by K. lactis K7 was increased to 173 U/ml, which is about 23% improvement in Biofilm Reactor and 57% improvement compared to the suspended-cell fermentation.
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continuous pullulan fermentation in a Biofilm Reactor
Applied Microbiology and Biotechnology, 2011Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Biofilm is a natural form of cell immobilization in which microorganisms attach onto solid support. In this study, a pigment-reduced pullulan-producing strain, Aureobasidium pullulans (ATCC 201253), was used for continuous pullulan fermentation in a plastic composite support (PCS) Biofilm Reactor. Optimal conditions for the continuous pullulan production were determined by evaluating the effects of the feeding medium with various concentrations of ammonium sulfate and sucrose and dilution rate. Pullulan concentration and production rate reached maximum (8.3 g/l and 1.33 g/l/h) when 15 g/l of sucrose, 0.9 g/l of ammonium sulfate, and 0.4 g/l of yeast extract were applied in the medium, and the dilution rate was at 0.16 h−1. The purity of produced pullulan was 93.0%. The ratio of hyphal cells of A. pullulans increased when it was grown on the PCS shaft. Overall, the increased pullulan productivity can be achieved through biomass retention by using PCS Biofilm Reactor.
Hallvard Ødegaard - One of the best experts on this subject based on the ideXlab platform.
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aerobic moving bed Biofilm Reactor treating thermomechanical pulping whitewater under thermophilic conditions
Water Research, 2002Co-Authors: Sigrun J Jahren, Jukka Rintala, Hallvard ØdegaardAbstract:Abstract The continuously operated laboratory scale Kaldnes moving bed Biofilm Reactor (MBBR) was used for thermophilic (55°C) aerobic treatment of TMP whitewater. In the MBBR, the biomass is grown on carrier elements that move along with the water in the Reactor. Inoculation with mesophilic activated sludge gave 60–65% SCOD removal from the first day onwards. During the 107 days of experiment, the 60–65% SCOD removals were achieved at organic loading rates of 2.5–3.5 kg SCOD m−3 d−1, the highest loading rates applied during the run and HRT of 13–22 h. Carbohydrates, which contributed to 50–60% of the influent SCOD, were removed by 90–95%, while less than 15% of the lignin-like material (30–35% of SCODin) was removed. The sludge yield was 0.23 g VSS g SCODremoved−1. The results show that the aerobic Biofilm process can be successfully operated under thermophilic conditions.
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The Moving Bed Biofilm Reactor
1999Co-Authors: Hallvard ØdegaardAbstract:A new Biofilm Reactor for wastewater treatment, the moving bed Biofilm Reactor (MBBR), is discussed. A general description of the Reactor is given. Results from investigations of different applications (carbonaceous removal, nitrification and nitrogen removal) when used for municipal wastewater treatment, are discussed. Design values are given and it is demonstrated that use of this Reactor results in very compact treatment plants .
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a new moving bed Biofilm Reactor applications and results
Water Science and Technology, 1994Co-Authors: Hallvard Ødegaard, Bjorn Rusten, T WestrumAbstract:A new moving bed Biofilm Reactor has been developed in Norway. The biomass is attached to carrier elements that move freely along with the water in the Reactor. It is demonstrated in the paper that this results in a very compact Reactor and a very efficient biomass. Experiences from pilot and full-scale testing of the Reactor in municipal and industrial wastewater treatment applications are presented and discussed.
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nitrification in a moving bed Biofilm Reactor
Water Research, 1994Co-Authors: Bjorn Rusten, Hallvard ØdegaardAbstract:Abstract A new Biofilm Reactor, the moving bed Reactor, was studied for nitrification purposes. The study was partly on laboratory-scale with a prepared water, and partly on pilot-scale with primary or secondary effluent as feed water. The experimental results showed that when alkalinity was in excess and there was no organic load, either the ammonium or the oxygen concentration would be limiting for the nitrification rate. The shift from the ammonium to the oxygen concentration being rate limiting occurred for an oxygen to ammonium concentration ratio of about 3 g O 2 (g NH 4 -N) −1 . The oxygen concentration had a great influence on the nitrification rate when oxygen was rate limiting. The nitrification rate was then close to a first-order function of the oxygen concentration, indicating liquid film diffusion to be the important rate limiting mechanism. Nitrification rates were reduced by increased organic loads. When the organic load exceeded 5 g total BOD 7 m 2 d −1 , the nitrification became insignificant. With a secondary effluent feed, nitrification rates of 0.7−1.0 g NO x -N (NO 3 -N + NO 2 -N) m −2 d −1 were achieved at oxygen concentrations between 4.5 and 5 g O 2 m −3 . Curves were constructed for nitrification at different organic loads when the oxygen concentration was rate limiting.
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Treatment of Dairy Wastewater in a Novel Moving Bed Biofilm Reactor
Water Science and Technology, 1992Co-Authors: Bjorn Rusten, Hallvard Ødegaard, Arne LundarAbstract:A novel moving bed Biofilm Reactor has been developed, where the Biofilm grows on small, free floating plastic elements with a large surface area and a density slightly less than 1.0 g/cm 3 . The specific Biofilm surface area can be regulated as required, up to a maximum of approximately 400 m 2 /m 3 . The ability to remove organic matter from concentrated industrial effluents was tested in an aerobic pilot-plant with two moving bed Biofilm Reactors in series and a specific Biofilm surface area of 276 m 2 /m 3 . Treating dairy wastewater, the pilot-plant showed 85% and 60% COD removal at volumetric organic loading rates of 500 g COD/m 3 h and 900 g COD/m 3 h respectively. Based on the test results, the moving bed Biofilm Reactors should be very suitable for treatment of food industry effluents.
Yan Zhang - One of the best experts on this subject based on the ideXlab platform.
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high thermostable ordered mesoporous sio2 tio2 coated circulating bed Biofilm Reactor for unpredictable photocatalytic and biocatalytic performance
Applied Catalysis B-environmental, 2016Co-Authors: Yan Zhang, Linlin Zhang, Zipeng Xing, Hang Zhang, Zhenzi Li, Xiaoyan Wu, Xiaodong Zhang, Wei ZhouAbstract:Abstract Utilizing high thermostable ordered mesoporous SiO2–TiO2 as a precursor, macroporous polyurethane foam (PUF) as a floating Biofilm carrier, the photocatalytic circulating-bed Biofilm Reactor (PCBBR) is fabricated via ultrasonic vibration and deposition approach. The prepared SiO2–TiO2/PUF carrier is characterized in detail by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption, scanning electron microscopy and energy dispersive spectroscopy. The results indicate that the ordered mesoporous SiO2–TiO2 network can be maintained and the presence of SiO2 can inhibit the anatase-to-rutile phase transformation during 800 °C calcinations. Furthermore, the prepared SiO2–TiO2/PUF carrier presents a hierarchical macro/mesoporous structure, filling the bacterium to the channels. The PCBBR exhibits good synergic effect for the refractory phenolic wastewater, and the total organic carbon removal ratio of high toxic 2,4,5-trichlorophenol is up to 97.5% after hydraulic retention time for 3 h, which is ascribed to the hierarchical macro/mesoporous structure in favor of pollutants adsorption, efficient photon utilization and microorganism loading. This novel ordered mesoporous SiO2–TiO2 coated circulating-bed Biofilm Reactor is promising in the environmental field.
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aging Biofilm from a full scale moving bed Biofilm Reactor characterization and enzymatic treatment study
Bioresource Technology, 2014Co-Authors: Hui Huang, Lili Ding, Jinju Geng, Ke Xu, Yan ZhangAbstract:Abstract Effective removal of aging Biofilm deserves to receive more attention. This study aimed to characterized aging Biofilm from a full-scale moving bed Biofilm Reactor treating pharmaceutical wastewater and evaluate the hydrolysis effects of Biofilm by different enzymatic treatments. Results from FTIR and biochemical composition analyses showed that it was a predominately organic-based Biofilm with the ratio of total protein (PN) to polysaccharide (PS) of 20.17. A reticular structure of extracellular polymeric matrix (EPM) with filamentous bacteria as the skeleton was observed on the basal layer through SEM–EDS test. Among the four commercial proteases and amylases from Genencor®, proteases were shown to have better performances than amylases either on the removal of MLSS and PN/MLSS or on DOC (i.e., dissolved organic carbon)/MLSS raising of Biofilm pellets. Difference of dynamic fluorescence characteristics of dissolved organic matters after treated by the two proteases indicated distinguishing mechanisms of the treating process.
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Effect of DO on simultaneous nitrification and denitrification in catching bed Biofilm Reactor
2011 International Conference on Electrical and Control Engineering, 2011Co-Authors: Yan Zhang, Yanqing Zhang, Hui Wang, Lili Wang, Zhengyang YangAbstract:In this study, effect of DO on simultaneous nitrification and denitrification in catching bed Biofilm Reactor were investigated, using three sets of parallel Reactors controlled with different DO concentration. The average removal rate of COD was reached at 87% over the range of 0~3mg/L of DO. Comparely, NH4+-N removal rate increased significantly with the increase of DO concentration. The optimize DO concentration was 2~3, the average removal rate of NH4+-N and TN were 91.6% and 64.4% respectively.
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Study on the Influence of DO to Simultaneous Nitrification and Denitrification in Catching Bed Biofilm Reactor
2010 International Conference on E-Product E-Service and E-Entertainment, 2010Co-Authors: Yan Zhang, Hui Wang, Yuebo Wang, Yanqing ZhangAbstract:Abstract- The nitrogen removal effect of catching bed Biofilm Reactor based on traditional Biofilm process was investigate. The result indicates, steady removal effect with 87.81% of average COD removal rate was achieved in various dissolved oxygen(DO) concentrations.When DO was between 0.7~1.1 mg/L, removal rate for NH4+-N and TN 94.7% ,53.8%,respectively.When DO was controlled in 1.2~2.0 mg/L, 94.7% of average NH4+-N removal rate and 79.66% of average TN removal rate were obtained. When DO was between 2.0~3.5 mg/L, average removal rates for NH4+-N and TN were 99.6% and 65.1% respectively. The optimal condition for nitrogen removal effect was with DO between 1.0~2.0 mg/L. pH was also a crucial factor for removal rates of NH4+-N and TN. The preferable effect for simultaneous nitrification and denitrification was found between 7.05~7.37 of pH.
Kuan-chen Cheng - One of the best experts on this subject based on the ideXlab platform.
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Application of mathematical models to ethanol fermentation in Biofilm Reactor with carob extract
Biomass Conversion and Biorefinery, 2019Co-Authors: Mustafa Germec, Kuan-chen Cheng, Ali Demirci, Mustafa Karhan, Irfan TurhanAbstract:Mathematical models not only ensure information about kinetic-metabolic nature of fermentations, but also facilitate their control and optimization. In the study, flexible ten models were evaluated and employed to describe the ethanol fermentation in a Biofilm Reactor with a carob extract medium (CEM). Findings indicated that W model well fitted the experimental data of cell growth (root mean square error (RMSE) = 0.289 g/L, mean absolute error (MAE) = 0.237 g/L, regression coefficient ( R ^ 2 ) = 0.9944, bias factor (BF) = 1.021, and accuracy factor (AF) = 1.047), ethanol production (RMSE = 1.609 g/L, MAE = 1.277 g/L, R ^ 2 = 0.9774, BF = 1.178, and AF = 1.283), and substrate consumption (RMSE = 2.493 g/L, MAE = 1.546 g/L, R ^ 2 = 0.9931, BF = 1.001 and AF = 1.053). In the prediction of kinetic parameters, W model also gave better and well-directed results compared with the other mathematical models used in the study. When an independent set of experimental data was used in the validation of mathematical models, similar validation results were obtained and W model was also successful. Consequently, W model could be used for more progress of fermentation process in Biofilm Reactor with CEM, which can serve as a universal equation.
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continuous pullulan fermentation in a Biofilm Reactor
Applied Microbiology and Biotechnology, 2011Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Biofilm is a natural form of cell immobilization in which microorganisms attach onto solid support. In this study, a pigment-reduced pullulan-producing strain, Aureobasidium pullulans (ATCC 201253), was used for continuous pullulan fermentation in a plastic composite support (PCS) Biofilm Reactor. Optimal conditions for the continuous pullulan production were determined by evaluating the effects of the feeding medium with various concentrations of ammonium sulfate and sucrose and dilution rate. Pullulan concentration and production rate reached maximum (8.3 g/l and 1.33 g/l/h) when 15 g/l of sucrose, 0.9 g/l of ammonium sulfate, and 0.4 g/l of yeast extract were applied in the medium, and the dilution rate was at 0.16 h−1. The purity of produced pullulan was 93.0%. The ratio of hyphal cells of A. pullulans increased when it was grown on the PCS shaft. Overall, the increased pullulan productivity can be achieved through biomass retention by using PCS Biofilm Reactor.
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Continuous Pullulan Fermentation in a PCS Biofilm Reactor
Applied Microbiology and Biotechnology, 2011Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Biofilms are natural form of cell immobilization in which microorganisms attach onto solid support. In this study, a pigment-reduced pullulan-producing strain, Aureobasidium pullulans (ATCC 201253), was used for continuous pullulan fermentation in a Plastic Composite Support (PCS) Biofilm Reactor. Optimal conditions for the continuous pullulan production were determined by evaluating the effects of the feeding medium (concentrations of ammonium sulfate and sucrose) and dilution rate. Pullulan concentration and production rate reached maximum (8.3 g/l and 1.33 g/l/h) when 15 g/l of sucrose, 0.9 g/l of ammonium sulfate and 0.4 g/l of yeast extract were applied in the medium, and the dilution rate was at 0.16 h-1. For system stability evaluation, A. pullulans produced equal amount of pullulan after 60 residence times, and the purity of produced pullulan was 93.0%. The ratio of hyphal form cells on the PCS increased since the solid support is more suitable for the attachment of filamentous cells. Overall, the increased pullulan productivity can be achieved through biomass retention by using PCS Biofilm Reactor.
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effects of plastic composite support and ph profiles on pullulan production in a Biofilm Reactor
Applied Microbiology and Biotechnology, 2010Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Pullulan is a linear homopolysaccharide which is composed of glucose units and often described as α-1, 6-linked maltotriose. The applications of pullulan range from usage as blood plasma substitutes to environmental pollution control agents. In this study, a Biofilm Reactor with plastic composite support (PCS) was evaluated for pullulan production using Aureobasidium pullulans. In test tube fermentations, PCS with soybean hulls, defatted soy bean flour, yeast extract, dried bovine red blood cells, and mineral salts was selected for Biofilm Reactor fermentation (due to its high nitrogen content, moderate nitrogen leaching rate, and high biomass attachment). Three pH profiles were later applied to evaluate their effects on pullulan production in a PCS Biofilm Reactor. The results demonstrated that when a constant pH at 5.0 was applied, the time course of pullulan production was advanced and the concentration of pullulan reached 32.9 g/L after 7-day cultivation, which is 1.8-fold higher than its respective suspension culture. The quality analysis demonstrated that the purity of produced pullulan was 95.8% and its viscosity was 2.4 centipoise. Fourier transform infrared spectroscopy spectra also supported the supposition that the produced exopolysaccharide was mostly pullulan. Overall, this study demonstrated that a Biofilm Reactor can be successfully implemented to enhance pullulan production and maintain its high purity.
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Enhanced production of bacterial cellulose by using a Biofilm Reactor and its material property analysis
Journal of Biological Engineering, 2009Co-Authors: Kuan-chen Cheng, Jeffrey M. Catchmark, Ali DemirciAbstract:Bacterial cellulose has been used in the food industry for applications such as low-calorie desserts, salads, and fabricated foods. It has also been used in the paper manufacturing industry to enhance paper strength, the electronics industry in acoustic diaphragms for audio speakers, the pharmaceutical industry as filtration membranes, and in the medical field as wound dressing and artificial skin material. In this study, different types of plastic composite support (PCS) were implemented separately within a fermentation medium in order to enhance bacterial cellulose (BC) production by Acetobacter xylinum. The optimal composition of nutritious compounds in PCS was chosen based on the amount of BC produced. The selected PCS was implemented within a bioReactor to examine the effects on BC production in a batch fermentation. The produced BC was analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among thirteen types of PCS, the type SFYR+ was selected as solid support for BC production by A. xylinum in a batch Biofilm Reactor due to its high nitrogen content, moderate nitrogen leaching rate, and sufficient biomass attached on PCS. The PCS Biofilm Reactor yielded BC production (7.05 g/L) that was 2.5-fold greater than the control (2.82 g/L). The XRD results indicated that the PCS-grown BC exhibited higher crystallinity (93%) and similar crystal size (5.2 nm) to the control. FESEM results showed the attachment of A. xylinum on PCS, producing an interweaving BC product. TGA results demonstrated that PCS-grown BC had about 95% water retention ability, which was lower than BC produced within suspended-cell Reactor. PCS-grown BC also exhibited higher Tmax compared to the control. Finally, DMA results showed that BC from the PCS Biofilm Reactor increased its mechanical property values, i.e., stress at break and Young's modulus when compared to the control BC. The results clearly demonstrated that implementation of PCS within agitated fermentation enhanced BC production and improved its mechanical properties and thermal stability.
Jeffrey M. Catchmark - One of the best experts on this subject based on the ideXlab platform.
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Continuous Pullulan Fermentation in a PCS Biofilm Reactor
Applied Microbiology and Biotechnology, 2011Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Biofilms are natural form of cell immobilization in which microorganisms attach onto solid support. In this study, a pigment-reduced pullulan-producing strain, Aureobasidium pullulans (ATCC 201253), was used for continuous pullulan fermentation in a Plastic Composite Support (PCS) Biofilm Reactor. Optimal conditions for the continuous pullulan production were determined by evaluating the effects of the feeding medium (concentrations of ammonium sulfate and sucrose) and dilution rate. Pullulan concentration and production rate reached maximum (8.3 g/l and 1.33 g/l/h) when 15 g/l of sucrose, 0.9 g/l of ammonium sulfate and 0.4 g/l of yeast extract were applied in the medium, and the dilution rate was at 0.16 h-1. For system stability evaluation, A. pullulans produced equal amount of pullulan after 60 residence times, and the purity of produced pullulan was 93.0%. The ratio of hyphal form cells on the PCS increased since the solid support is more suitable for the attachment of filamentous cells. Overall, the increased pullulan productivity can be achieved through biomass retention by using PCS Biofilm Reactor.
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continuous pullulan fermentation in a Biofilm Reactor
Applied Microbiology and Biotechnology, 2011Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Biofilm is a natural form of cell immobilization in which microorganisms attach onto solid support. In this study, a pigment-reduced pullulan-producing strain, Aureobasidium pullulans (ATCC 201253), was used for continuous pullulan fermentation in a plastic composite support (PCS) Biofilm Reactor. Optimal conditions for the continuous pullulan production were determined by evaluating the effects of the feeding medium with various concentrations of ammonium sulfate and sucrose and dilution rate. Pullulan concentration and production rate reached maximum (8.3 g/l and 1.33 g/l/h) when 15 g/l of sucrose, 0.9 g/l of ammonium sulfate, and 0.4 g/l of yeast extract were applied in the medium, and the dilution rate was at 0.16 h−1. The purity of produced pullulan was 93.0%. The ratio of hyphal cells of A. pullulans increased when it was grown on the PCS shaft. Overall, the increased pullulan productivity can be achieved through biomass retention by using PCS Biofilm Reactor.
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effects of plastic composite support and ph profiles on pullulan production in a Biofilm Reactor
Applied Microbiology and Biotechnology, 2010Co-Authors: Kuan-chen Cheng, Ali Demirci, Jeffrey M. CatchmarkAbstract:Pullulan is a linear homopolysaccharide which is composed of glucose units and often described as α-1, 6-linked maltotriose. The applications of pullulan range from usage as blood plasma substitutes to environmental pollution control agents. In this study, a Biofilm Reactor with plastic composite support (PCS) was evaluated for pullulan production using Aureobasidium pullulans. In test tube fermentations, PCS with soybean hulls, defatted soy bean flour, yeast extract, dried bovine red blood cells, and mineral salts was selected for Biofilm Reactor fermentation (due to its high nitrogen content, moderate nitrogen leaching rate, and high biomass attachment). Three pH profiles were later applied to evaluate their effects on pullulan production in a PCS Biofilm Reactor. The results demonstrated that when a constant pH at 5.0 was applied, the time course of pullulan production was advanced and the concentration of pullulan reached 32.9 g/L after 7-day cultivation, which is 1.8-fold higher than its respective suspension culture. The quality analysis demonstrated that the purity of produced pullulan was 95.8% and its viscosity was 2.4 centipoise. Fourier transform infrared spectroscopy spectra also supported the supposition that the produced exopolysaccharide was mostly pullulan. Overall, this study demonstrated that a Biofilm Reactor can be successfully implemented to enhance pullulan production and maintain its high purity.
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Enhanced production of bacterial cellulose by using a Biofilm Reactor and its material property analysis
Journal of Biological Engineering, 2009Co-Authors: Kuan-chen Cheng, Jeffrey M. Catchmark, Ali DemirciAbstract:Bacterial cellulose has been used in the food industry for applications such as low-calorie desserts, salads, and fabricated foods. It has also been used in the paper manufacturing industry to enhance paper strength, the electronics industry in acoustic diaphragms for audio speakers, the pharmaceutical industry as filtration membranes, and in the medical field as wound dressing and artificial skin material. In this study, different types of plastic composite support (PCS) were implemented separately within a fermentation medium in order to enhance bacterial cellulose (BC) production by Acetobacter xylinum. The optimal composition of nutritious compounds in PCS was chosen based on the amount of BC produced. The selected PCS was implemented within a bioReactor to examine the effects on BC production in a batch fermentation. The produced BC was analyzed using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Among thirteen types of PCS, the type SFYR+ was selected as solid support for BC production by A. xylinum in a batch Biofilm Reactor due to its high nitrogen content, moderate nitrogen leaching rate, and sufficient biomass attached on PCS. The PCS Biofilm Reactor yielded BC production (7.05 g/L) that was 2.5-fold greater than the control (2.82 g/L). The XRD results indicated that the PCS-grown BC exhibited higher crystallinity (93%) and similar crystal size (5.2 nm) to the control. FESEM results showed the attachment of A. xylinum on PCS, producing an interweaving BC product. TGA results demonstrated that PCS-grown BC had about 95% water retention ability, which was lower than BC produced within suspended-cell Reactor. PCS-grown BC also exhibited higher Tmax compared to the control. Finally, DMA results showed that BC from the PCS Biofilm Reactor increased its mechanical property values, i.e., stress at break and Young's modulus when compared to the control BC. The results clearly demonstrated that implementation of PCS within agitated fermentation enhanced BC production and improved its mechanical properties and thermal stability.
