Siderophore production by Fusarium venenatum A3/5

2002 ◽  
Vol 30 (4) ◽  
pp. 696-698 ◽  
Author(s):  
M. G. Wiebe
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Environmental Conditions ◽  
Continuous Flow ◽  
Specific Growth ◽  
Chemostat Culture ◽  
Siderophore Production ◽  
Batch Cultures ◽  
Chemostat Cultures ◽  
Fusarium Venenatum

Fusarium venenatum A3/5 was grown in iron-restricted batch cultures and iron-limited chemostat cultures to determine how environmental conditions affected siderophore production. The specific growth rate in iron-restricted batch cultures was 0.22 h−1, which was reduced to 0.12 h−1 when no iron was added to the culture. Derit in iron-limited chemostat culture was 0.1 h−1. Siderophore production was correlated with specific growth rate, with the highest siderophore production occurring at D = 0.08 h−1 and the lowest at D = 0.03 h−1. Siderophore production was greatest at pH 4.7 and was significantly reduced at pHs above 6.0. Siderophore production could be enhanced by providing insoluble iron instead of soluble iron in continuous flow cultures.

scholarly journals Influence of Carbon Source on Nitrate Removal by Nitrate-TolerantKlebsiella oxytoca CECT 4460 in Batch and Chemostat Cultures

1998 ◽  
Vol 64 (8) ◽  
pp. 2970-2976 ◽  
Author(s):  
Guadalupe Piñar ◽  
Karin Kovárová ◽  
Thomas Egli ◽  
Juan L. Ramos
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Nitrate Removal ◽  
Dry Weight ◽  
Specific Rate ◽  
Continuous Cultures ◽  
Batch Cultures ◽  
Chemostat Cultures ◽  
C And N

ABSTRACT The nitrate-tolerant organism Klebsiella oxytoca CECT 4460 tolerates nitrate at concentrations up to 1 M and is used to treat wastewater with high nitrate loads in industrial wastewater treatment plants. We studied the influence of the C source (glycerol or sucrose or both) on the growth rate and the efficiency of nitrate removal under laboratory conditions. With sucrose as the sole C source the maximum specific growth rate was 0.3 h−1, whereas with glycerol it was 0.45 h−1. In batch cultures K. oxytocacells grown on sucrose or glycerol were able to immediately use sucrose as a sole C source, suggesting that sucrose uptake and metabolism were constitutive. In contrast, glycerol uptake occurred preferentially in glycerol-grown cells. Independent of the preculture conditions, when sucrose and glycerol were added simultaneously to batch cultures, the sucrose was used first, and once the supply of sucrose was exhausted, the glycerol was consumed. Utilization of nitrate as an N source occurred without nitrite or ammonium accumulation when glycerol was used, but nitrite accumulated when sucrose was used. In chemostat cultures K. oxytoca CECT 4460 efficiently removed nitrate without accumulation of nitrate or ammonium when sucrose, glycerol, or mixtures of these two C sources were used. The growth yields and the efficiencies of C and N utilization were determined at different growth rates in chemostat cultures. Regardless of the C source, yield carbon (YC) ranged between 1.3 and 1.0 g (dry weight) per g of sucrose C or glycerol C consumed. Regardless of the specific growth rate and the C source, yield nitrogen (YN) ranged from 17.2 to 12.5 g (dry weight) per g of nitrate N consumed. In contrast to batch cultures, in continuous cultures glycerol and sucrose were utilized simultaneously, although the specific rate of sucrose consumption was higher than the specific rate of glycerol consumption. In continuous cultures double-nutrient-limited growth appeared with respect to the C/N ratio of the feed medium and the dilution rate, so that for a C/N ratio between 10 and 30 and a growth rate of 0.1 h−1 the process led to simultaneous and efficient removal of the C and N sources used. At a growth rate of 0.2 h−1the zone of double limitation was between 8 and 11. This suggests that the regimen of double limitation is influenced by the C/N ratio and the growth rate. The results of these experiments were validated by pulse assays.

Influence of specific growth rate over the secretory expression of recombinant potato carboxypeptidase inhibitor in fed-batch cultures of Escherichia coli

2010 ◽  
Vol 45 (8) ◽  
pp. 1334-1341 ◽  
Author(s):  
Juan-Miguel Puertas ◽  
Jordi Ruiz ◽  
Mónica Rodríguez de la Vega ◽  
Julia Lorenzo ◽  
Glòria Caminal ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Fed Batch ◽  
Secretory Expression ◽  
Batch Cultures ◽  
Carboxypeptidase Inhibitor

Specific growth rate and not cell density controls the general stress response in Escherichia coli

Microbiology ◽  
2004 ◽  
Vol 150 (6) ◽  
pp. 1637-1648 ◽  
Author(s):  
Julian Ihssen ◽  
Thomas Egli
Keyword(s):  
Escherichia Coli ◽  
Growth Rate ◽  
Stress Response ◽  
Specific Growth Rate ◽  
Cell Density ◽  
Specific Growth ◽  
Batch Cultures ◽  
General Stress Response ◽  
E Coli ◽  
Density Effects

In batch cultures of Escherichia coli, the intracellular concentration of the general stress response sigma factor RpoS typically increases during the transition from the exponential to the stationary growth phase. However, because this transition is accompanied by complex physico-chemical and biological changes, which signals predominantly elicit this induction is still the subject of debate. Careful design of the growth environment in chemostat and batch cultures allowed the separate study of individual factors affecting RpoS. Specific growth rate, and not cell density or the nature of the growth-limiting nutrient, controlled RpoS expression and RpoS-dependent hydroperoxidase activity. Furthermore, it was demonstrated that the standard E. coli minimal medium A (MMA) is not suitable for high-cell-density cultivation because it lacks trace elements. Previously reported cell-density effects in chemostat cultures of E. coli can be explained by a hidden, secondary nutrient limitation, which points to the importance of medium design and appropriate experimental set-up for studying cell-density effects.

scholarly journals Control of Specific Growth Rate in Fed-Batch Bioprocesses: Novel Controller Design for Improved Noise Management

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 679 ◽  
Author(s):  
Yann Brignoli ◽  
Brian Freeland ◽  
David Cunningham ◽  
Michal Dabros
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Real Time ◽  
Specific Growth ◽  
Controller Design ◽  
Control Variable ◽  
Biomass Concentration ◽  
Growth Dynamics ◽  
Fed Batch ◽  
Batch Cultures

Accurate control of the specific growth rate (µ) of microorganisms is dependent on the ability to quantify the evolution of biomass reliably in real time. Biomass concentration can be monitored online using various tools and methods, but the obtained signal is often very noisy and unstable, leading to inaccuracies in the estimation of μ. Furthermore, controlling the growth rate is challenging as the process evolves nonlinearly and is subject to unpredictable disturbances originating from the culture’s metabolism. In this work, a novel feedforward-feedback controller logic is presented to counter the problem of noise and oscillations in the control variable and to address the exponential growth dynamics more effectively. The controller was tested on fed-batch cultures of Kluyveromyces marxianus, during which μ was estimated in real time from online biomass concentration measurements obtained with dielectric spectroscopy. It is shown that the specific growth rate can be maintained at different setpoint values with an average root mean square control error of 23 ± 6%.

scholarly journals Phenol Degradation Kinetics by Free and Immobilized Pseudomonas putida BCRC 14365 in Batch and Continuous-Flow Bioreactors

Processes ◽  
2020 ◽  
Vol 8 (6) ◽  
pp. 721
Author(s):  
Yen-Hui Lin ◽  
Yu-Siang Cheng
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Pseudomonas Putida ◽  
Growth Phase ◽  
Continuous Flow ◽  
Specific Growth ◽  
Immobilized Cells ◽  
Phenol Degradation ◽  
Exponential Growth Phase ◽  
Steady State Condition

Phenol degradation by Pseudomonas putida BCRC 14365 was investigated at 30 °C and a pH of 5.0–9.0 in the batch tests. Experimental results for both free and immobilized cells demonstrated that a maximum phenol degradation rate occurred at an initial pH of 7. The peak value of phenol degradation rates by the free and immobilized cells were 2.84 and 2.64 mg/L-h, respectively. Considering the culture at 20 °C, there was a lag period of approximately 44 h prior to the start of the phenol degradation for both free and immobilized cells. At the temperatures ranging from 25 to 40 °C, the immobilized cells had a higher rate of phenol degradation compared to the free cells. Moreover, the removal efficiencies of phenol degradation at the final stage were 59.3–92% and 87.5–92%, for the free and immobilized cells, respectively. The optimal temperature was 30 °C for free and immobilized cells. In the batch experiments with various initial phenol concentrations of 68.3–563.4 mg/L, the lag phase was practically negligible, and a logarithmic growth phase of a particular duration was observed from the beginning of the culture. The specific growth rate (μ) in the exponential growth phase was 0.085–0.192 h−1 at various initial phenol concentrations between 68.3 and 563.4 mg/L. Comparing experimental data with the Haldane kinetics, the biokinetic parameters, namely, maximum specific growth rate (μmax), the phenol half-saturation constant (Ks) and the phenol inhibition constant (KI), were determined to equal 0.31 h−1, 26.2 mg/L and 255.0 mg/L, respectively. The growth yield and decay coefficient of P. putida cells were 0.592 ± 4.995 × 10−3 mg cell/mg phenol and 5.70 × 10−2 ± 1.122 × 10−3 day−1, respectively. A completely mixed and continuous-flow bioreactor with immobilized cells was set up to conduct the verification of the kinetic model system. The removal efficiency for phenol in the continuous-flow bioreactor was approximately 97.7% at a steady-state condition. The experimental and simulated methodology used in this work can be applied, in the design of an immobilized cell process, by various industries for phenol-containing wastewater treatment.

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