The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Jochen Buchs - One of the best experts on this subject based on the ideXlab platform.
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Effect of the Oxygen Transfer Rate on Oxygen-limited production of plasmid DNA by Escherichia coli
Biochemical Engineering Journal, 2019Co-Authors: Alvaro R. Lara, Karim E. Jaén, Olusegun Folarin, Eli Keshavarz-moore, Jochen BuchsAbstract:Abstract The influence of Oxygen limitation on pDNA yields in cultures of Escherichia coli was studied. Cultures at maximum Oxygen Transfer Rate (OTRmax) values of 10, 14, 30 and 45 mmol L−1 h−1 and an aerobic culture at an OTRmax of 110 mmol L−1 h−1 were performed in microtiter plates (MTPs). Dissolved Oxygen tension (DOT), pH, biomass and NADH fluorescence were monitored online. An E. coli strain that constitutively expresses Vitreoscilla hemoglobin (VHb) was used and compared with its parent strain. pDNA yields were inversely proportional to the OTRmax for both strains and increased more than two-fold in cultures at the lowest OTRmax compared with that in aerobic cultures. Expression of VHb increased the specific growth Rate at OTRmax values of 10, 14 and 30 mmol L−1 h−1 compared with that of the parent strain. NADH-specific fluorescence decreased in cultures of the engineered strain. The pDNA supercoiled fraction (SCF) was greatest in cultures at an OTRmax of 30 mmol L−1 h−1, reaching 92.9% for the wild type strain and 98.7% for the VHb-expressing strain, while no linearized pDNA was detected. This condition was replicated in a 1 L stirred tank bioreactor, and the results closely resembled those of cultures in MTPs.
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Investigation of poly(γ-glutamic acid) production via online determination of viscosity and Oxygen Transfer Rate in shake flasks
Journal of biological engineering, 2017Co-Authors: Lena Meissner, Julia Arndt, Thomas G. Palmen, Tim Jestel, Hitoshi Mitsunaga, Eiichiro Fukusaki, Jochen BuchsAbstract:Poly(γ-glutamic acid) (γ-PGA) is a biopolymer with many useful properties making it applicable for instance in food and skin care industries, in wastewater treatment, in biodegradable plastics or in the pharmaceutical industry. γ-PGA is usually produced microbially by different Bacillus spp. The produced γ-PGA increases the viscosity of the fermentation broth. In case of shake flask fermentations, this results in an increase of the volumetric power input. The power input in shake flasks can be determined by measuring the torque of an orbitally rotating lab shaker. The online measurement of the volumetric power input enables to continuously monitor the formation or degradation of viscous products like γ-PGA. Combined with the online measurement of the Oxygen Transfer Rate (OTR), the respiration activity of the organisms can be observed at the same time. Two different Bacillus licheniformis strains and three medium compositions were investigated using online volumetric power input and OTR measurements as well as thorough offline analysis. The online volumetric power input measurement clearly depicted changes in γ-PGA formation due to different medium compositions as well as differences in the production behavior of the two investigated strains. A higher citric acid concentration and the addition of trace elements to the standard medium showed a positive influence on γ-PGA production. The online power input signal was used to derive an online viscosity signal which was validated with offline determined viscosity values. The online measurement of the OTR proved to be a valuable tool to follow the respiration activity of the cultivated strains and to determine its reproducibility under different cultivation conditions. The combination of the volumetric power input and the OTR allows for an easy and reliable investigation of new strains, cultivation conditions and medium compositions for their potential in γ-PGA production. The power input signal and the derived online viscosity directly reflect changes in γ-PGA molecular weight and concentration, respectively, due to different cultivation conditions or production strains.
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Quasi-continuous parallel online scattered light, fluorescence and dissolved Oxygen tension measurement combined with monitoring of the Oxygen Transfer Rate in each well of a shaken microtiter plate
Microbial cell factories, 2016Co-Authors: Tobias Ladner, Markus Held, David Flitsch, Mario Beckers, Jochen BuchsAbstract:Background Microtiter plates (MTP) are often applied as culture vessels in high-throughput screening programs. If online measuring techniques are available, MTPs can also be applied in the first steps of process development. For such small-scale bioreactors dipping probes are usually too large; therefore, optical measurements are often used. For example, the BioLector technology allows for the online monitoring of scattered light and fluorescence in each well of a continuously orbitally shaken MTP. Although this system provides valuable data, these measurements are mainly of a semi-quantitative nature. Therefore, signal calibration is required to obtain absolute values. With the µRAMOS technology it became possible for the first time to quantify the Oxygen Transfer Rate (OTR) sepaRately in each well of an MTP. In this work, a device is presented that combines both techniques, to provide a hitherto unparalleled high amount of information from each single well.
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RESEARCH ARTICLE Open Access Oxygen Transfer Rate identifies priming compounds in parsley cells
2016Co-Authors: Jana Viola Schilling, Britta Schillheim, Stefan Mahr, Yannik Reufer, Uwe Conrath, I Sanjoyo, Jochen BuchsAbstract:Background: In modern agriculture, the call for an alternative crop protection stRategy increases because of the desired reduction of fungicide and pesticide use and the continuously evolving resistance of pathogens and pests to agrochemicals. The direct activation of the plant immune system does not provide a promising plant protection measure because of high fitness costs. However, upon treatment with certain natural or synthetic compounds, plant cells can promote to a fitness cost-saving, primed state of enhanced defense. In the primed state, plants respond to biotic and abiotic stress with faster and stronger activation of defense, and this is often associated with immunity and abiotic stress tolerance. Until now, the identification of chemical compounds with priming-inducing activity (so-called plant activators) relied on tedious and invasive approaches, or required the late detection of secreted furanocoumarin phytoalexins in parsley cell cultures. Thus, simple, fast, straightforward, and noninvasive techniques for identifying priming-inducing compounds for plant protection are very welcome. Results: This report demonstRates that a respiration activity-monitoring system (RAMOS) can identify compounds with defense priming-inducing activity in parsley cell suspension in culture. RAMOS relies on the quasi-continuous, noninvasive online determination of the Oxygen Transfer Rate (OTR). Treatment of parsley culture cells with the known plant activator salicylic acid (SA), a natural plant defense signal, resulted in an OTR increase. Addition of th
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Oxygen Transfer Rate identifies priming compounds in parsley cells
BMC Plant Biology, 2015Co-Authors: Jana Viola Schilling, Britta Schillheim, Stefan Mahr, Yannik Reufer, Sandi Sanjoyo, Uwe Conrath, Jochen BuchsAbstract:Background In modern agriculture, the call for an alternative crop protection stRategy increases because of the desired reduction of fungicide and pesticide use and the continuously evolving resistance of pathogens and pests to agrochemicals. The direct activation of the plant immune system does not provide a promising plant protection measure because of high fitness costs. However, upon treatment with certain natural or synthetic compounds, plant cells can promote to a fitness cost-saving, primed state of enhanced defense. In the primed state, plants respond to biotic and abiotic stress with faster and stronger activation of defense, and this is often associated with immunity and abiotic stress tolerance. Until now, the identification of chemical compounds with priming-inducing activity (so-called plant activators) relied on tedious and invasive approaches, or required the late detection of secreted furanocoumarin phytoalexins in parsley cell cultures. Thus, simple, fast, straightforward, and noninvasive techniques for identifying priming-inducing compounds for plant protection are very welcome.
W.h. Rulkens - One of the best experts on this subject based on the ideXlab platform.
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Temperature effects on the Oxygen Transfer Rate between 20 and 55°C
Water Research, 2000Co-Authors: J.c.t. Vogelaar, A. Klapwijk, J.b. Van Lier, W.h. RulkensAbstract:Abstract The influence of temperature on the Oxygen Transfer Rate (OTR) was studied in a bubble column. Aeration took place in three different liquids: tapwater, anaerobically pretreated paper process water and thermophilic sludge grown on a mineral medium and volatile fatty acids as carbon source. The OTR was measured in a temperature range of 20–55°C in case of tap- and process water. The OTR in the thermophilic sludge was determined at 55°C.The OTR remained constant over the specified temperature range in case of tapwater and showed a slight increase in case of process water. The constant OTR in case of tapwater was due to the counteracting effect of an increased overall Oxygen Transfer coefficient versus the decreased Oxygen saturation concentration at higher temperatures. At 55°C the OTR in the thermophilic sludge was comparable to both other liquids at this temperature.
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temperature effects on the Oxygen Transfer Rate between 20 and 55 c
Water Research, 2000Co-Authors: J.c.t. Vogelaar, A. Klapwijk, J.b. Van Lier, W.h. RulkensAbstract:Abstract The influence of temperature on the Oxygen Transfer Rate (OTR) was studied in a bubble column. Aeration took place in three different liquids: tapwater, anaerobically pretreated paper process water and thermophilic sludge grown on a mineral medium and volatile fatty acids as carbon source. The OTR was measured in a temperature range of 20–55°C in case of tap- and process water. The OTR in the thermophilic sludge was determined at 55°C.The OTR remained constant over the specified temperature range in case of tapwater and showed a slight increase in case of process water. The constant OTR in case of tapwater was due to the counteracting effect of an increased overall Oxygen Transfer coefficient versus the decreased Oxygen saturation concentration at higher temperatures. At 55°C the OTR in the thermophilic sludge was comparable to both other liquids at this temperature.
Xiaohong Zhou - One of the best experts on this subject based on the ideXlab platform.
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Use of the glucose oxidase system for estimation of Oxygen Transfer Rate in a solid-state bioreactor
Enzyme and Microbial Technology, 2002Co-Authors: Hua Zhao, Xiaoyong Zhang, Xiaohong ZhouAbstract:The glucose oxidase system was adapted for estimation of the overall Oxygen Transfer Rate in a periodic pressure oscillating, solid-state bioreactor. Enzyme concentration of 40 ml enzyme preparation L-1 was found adequate to give linear gluconic acid production and attain maximal Oxygen absorption Rates. At 4 atm and 30degreesC, the Oxygen Transfer Rate reached 892 mmol kg(-1) initial dry matter h(-1) in this system, while only 121 mmol kg(-1) initial dry matter h(-1) was obtained in a conventional static tray bioreactor. (C) 2002 Elsevier Science Inc. All rights reserved.
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Effects of air pressure oscillation amplitude on Oxygen Transfer Rate and biomass productivity in a solid-state fermenter
Biotechnology Letters, 2001Co-Authors: Hua Zhao, Xiaoyong Zhang, Xiaohong ZhouAbstract:The modified sulfite oxidation method was adapted for estimation of the overall Oxygen Transfer Rate in a pressure oscillating, solid-state fermenter. At 4.5 atm and 30 °C, the Oxygen Transfer Rate reached 717 mmol kg−1 initial dry matter h−1 in this system against 37 mmol kg−1 initial dry matter h−1 in a static tray fermenter. At 30 °C and 3 atm, Azotobacter vinelandii grew on wheat straw and reached 4.7×1010 c.f.u. g−1 substRate dry matter after 36 h, while only 8.2×109 c.f.u. g−1 substRate dry matter was obtained in a static tray system.
George T. Tsao - One of the best experts on this subject based on the ideXlab platform.
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Effects of pressure pulsation on Oxygen Transfer Rate measured by sulfite method.
Biotechnology for Fuels and Chemicals, 2003Co-Authors: Wei-cho Huang, Cheng S. Gong, George T. TsaoAbstract:Pressure pulsation (PP) was investigated for its effects on Oxygen Transfer Rate (OTR) measured by sulfite oxidation. By manipulating airflow Rate, 0.41–1.2 vvm, and a control valve in a 4-L bioreactor, the frequency of PP was varied at different gas pressures3–15 psig. A mathematical model of OTR was built and compared to experimental data. OTR was also examined at constant gas pressure, 4.5–15.0 psig. The results indicate a good agreement between measurement and model prediction. OTR above 9 psig during PP showed significant enhancement at 25°C. This proves that PP not only affects the elevation of DO level, but also increases the interfacial area and mass Transfer coefficient.
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Effects of pressure pulsation on Oxygen Transfer Rate measured by sulfite method.
Applied biochemistry and biotechnology, 2003Co-Authors: Wei-cho Huang, Cheng S. Gong, George T. TsaoAbstract:Pressure pulsation (PP) was investigated for its effects on Oxygen Transfer Rate (OTR) measured by sulfite oxidation. By manipulating airflow Rate, 0.41- 1.2 vvm, and a control valve in a 4-L bioreactor, the frequency of PP was varied at different gas pressures3-15 psig. A mathematical model of OTR was built and compared to experimental data. OTR was also examined at constant gas pressure, 4.5-15.0 psig. The results indicate a good agreement between measurement and model prediction. OTR above 9 psig during PP showed significant enhancement at 25 degrees C. This proves that PP not only affects the elevation of DO level, but also increases the interfacial area and mass Transfer coefficient.
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Optimization of 2,3-butanediol production by Klebsiella oxytoca through Oxygen Transfer Rate control.
Biotechnology and bioengineering, 1993Co-Authors: Peter B. Beronio, George T. TsaoAbstract:Production of 2,3-butanediol by Klebsiella oxytoca is influenced by the degree of Oxygen limitation. During batch culture studies, two phases of growth are observed: energy-coupled growth, during which cell growth and Oxygen supply are coupled; and, energy-uncoupled growth, which arises when the degree of Oxygen limitation reaches a critical value. Optimal 2,3-butanediol productivity occurs during the energy-coupled growth phase. In this article, a control system which maintains the batch culture at a constant level of Oxygen limitation in the energy-coupled growth regime has been designed. Control, which involves feedback control on the Oxygen Transfer coefficient, is achieved by continually increasing the partial pressure of Oxygen in the feed gas, which in turn continually increases the Oxygen Transfer Rate. Control has resulted in a balanced state of growth, a repression of ethanol formation, and an increase in 2,3-butanediol productivity of 18%.
Enrique Galindo - One of the best experts on this subject based on the ideXlab platform.
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Oxygen Transfer Rate during the production of alginate by azotobacter vinelandii under Oxygen limited and non Oxygen limited conditions
Microbial Cell Factories, 2011Co-Authors: Esteban Lozano, Enrique Galindo, Carlos PenaAbstract:Background The Oxygen Transfer Rate (OTR) and dissolved Oxygen tension (DOT) play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum Oxygen Transfer Rate (OTRmax) in cultures where the dissolved Oxygen tension (DOT) was kept constant.
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Oxygen Transfer Rate during the production of alginate by Azotobacter vinelandii under Oxygen-limited and non Oxygen-limited conditions
Microbial Cell Factories, 2011Co-Authors: Esteban Lozano, Enrique Galindo, Carlos F PeñaAbstract:Background The Oxygen Transfer Rate (OTR) and dissolved Oxygen tension (DOT) play an important role in determining alginate production and its composition; however, no systematic study has been reported about the independent influence of the OTR and DOT. In this paper, we report a study about alginate production and the evolution of the molecular mass of the polymer produced by a wild-type A. vinelandii strain ATCC 9046, in terms of the maximum Oxygen Transfer Rate (OTR_max) in cultures where the dissolved Oxygen tension (DOT) was kept constant. Results The results revealed that in the two dissolved Oxygen conditions evaluated, strictly controlled by gas blending at 0.5 and 5% DOT, an increase in the agitation Rate (from 300 to 700 rpm) caused a significant increase in the OTR_max (from 17 to 100 mmol L^-1 h^-1 for DOT of 5% and from 6 to 70 mmol L^-1 h^-1 for DOT of 0.5%). This increase in the OTR_max improved alginate production, as well as the specific alginate production Rate (SAPR), reaching a maximal alginate concentration of 3.1 g L^-1 and a SAPR of 0.031 g _alg g _biom^-1 h^-1 in the cultures at OTR_max of 100 mmol L^-1 h^-1. In contrast, the mean molecular mass (MMM) of the alginate isolated from cultures developed under non-Oxygen limited conditions increased by decreasing the OTR_max, reaching a maximal of 550 kDa at an OTR_max of 17 mmol L^-1 h^-1 . However, in the cultures developed under Oxygen limitation (0.5% DOT), the MMM of the polymer was practically the same (around 200 kDa) at 300 and 700 rpm, and this remained constant throughout the cultivation. Conclusions Overall, our results showed that under Oxygen-limited and non Oxygen-limited conditions, alginate production and its molecular mass are linked to the OTR_max, independently of the DOT of the culture.
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The viscosifying power, degree of acetylation and molecular mass of the alginate produced by Azotobacter vinelandii in shake flasks are determined by the Oxygen Transfer Rate
Process Biochemistry, 2011Co-Authors: Carlos Pena, Enrique Galindo, Jochen BuchsAbstract:Abstract The objective of this study was to evaluate the influence of the specific power input and Oxygen Transfer Rate (OTR) on changes in the alginate quality, in terms of the viscosifying power, molecular mass and degree of acetylation, of the polymer produced by Azotobacter vinelandii in shake flasks. Decreasing the shaking frequency from 200 to 100 rpm decreased the maximal volumetric power input ( P / V ) max from a maximal value of 1.5 kW m −3 to a minimal value of 0.23 kW m −3 . As a result of the decrease in the maximal volumetric power input, the maximum Oxygen Transfer Rate (OTR max ) decreased from 6 mmol L −1 h −1 to 2.6 mmol L −1 h −1 and the RQ (respiratory quotient) increased from 0.95 to 1.21 for the lower and higher power input, respectively. A lower RQ value was associated with the highest conversion value of carbon source (sucrose) to alginate. In contrast, at lower OTR max values, culture broths with a higher viscosity were obtained. Thus, for the same alginate concentration (∼3.0 g L −1 ), the viscosity of cultures at an OTR max value of 2.26 mmol L −1 h −1 was twice as high with respect to the viscosity observed in the culture broth obtained at a higher power input (OTR max = 6.0 mmol L −1 h −1 ). In addition, under lower power input (lower OTR), the molecular mass and the degree of acetylation of the polymer were the highest. Additional experiments in a stirred bioreactor under constant DOT and agitation Rate showed that under non-Oxygen-limited conditions (5% of DOT), the alginate yield and the molecular mass of the polymer are determined by the OTR and are independent of the agitation Rate of the culture.
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the Oxygen Transfer Rate influences the molecular mass of the alginate produced by azotobacter vinelandii
Applied Microbiology and Biotechnology, 2007Co-Authors: Alvaro Diazbarrera, Carlos Pena, Enrique GalindoAbstract:The influence of Oxygen Transfer Rate (OTR) on the molecular mass of alginate was studied. In batch cultures without dissolved Oxygen tension (DOT) control and at different agitation Rates, the DOT was nearly zero and the OTR was constant during biomass growth, hence the cultures were Oxygen-limited. The OTR reached different maximum levels (OTRmax) and enabled to establish various relative respiration Rates. Overall, the findings showed that OTR influences alginate molecular mass. The mean molecular mass (MMM) of the alginate increased as OTRmax decreased. The molecular mass obtained at 3.0 mmol l−1 h−1 was 7.0 times higher (1,560 kDa) than at 9.0 mmol l−1 h−1 (220 kDa). An increase in molecular mass can be a bacterial response to adverse nutritional conditions such as Oxygen limitation.
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Evolution of the specific power consumption and Oxygen Transfer Rate in alginate-producing cultures of Azotobacter vinelandii conducted in shake flasks
Biochemical Engineering Journal, 2007Co-Authors: Carlos Pena, Jochen Buchs, Cyril P. Peter, Enrique GalindoAbstract:Abstract The evolution of the specific power consumption and the Oxygen Transfer Rate occurring in shake flasks was studied in cultures of Azotobacter vinelandii , which synthesize alginate, a polymer producing non-Newtonian fermentation broths. Power consumption increased exponentially during the course of the fermentation (up to 1.4 kW m −3 ) due to an increase in the viscosity of the culture broth. This increase in the viscosity was associated with alginate concentration and the mean molecular mass of the polymer, which reached a maximum of 550 kDa after 50 h of cultivation. At the end of the fermentation, when the viscosity and alginate concentration reached a maximum, a slight drop in the power consumption was observed. This was probably because the fluid was in the “out-of-phase” state due to the high viscosity. In order to explain the “out of phase” behavior, the actual shear Rate in the shake flasks should be close to 90 s −1 . Although the on-line measurements of Oxygen Transfer Rate showed clear differences in the different filling volumes evaluated, both biomass growth and alginate production were very similar in the three conditions tested. Analysis of molecular mass distributions of the alginates suggests that, in the shake flasks cultures, DOT conditions can be more homogeneous than those present in a stirred fermentor without control of DOT and pH.
