Dissolved Carbon Dioxide Measurement and Its Correlation with Operating Parameters in Fermentation Processes

Dahod, Samun K.

doi:10.1021/bp00024a014

Cited by 24 publications

(17 citation statements)

References 9 publications

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“…pCO 2 in the liquid phase is assumed to be in equilibrium to the gas phase CO 2 according to Henry’s law in an ideally mixed tank because the limiting step in gas exchange is the diffusion of CO 2 in the liquid phase. Results from literature confirm this, at least for non-viscous culture broths where gas diffusion is not hindered [15,16]. …”

Section: Resultssupporting

confidence: 59%

Methods to optimize myxobacterial fermentations using off-gas analysis

Hüttel

Müller

2012

Microb Cell Fact

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BackgroundThe influence of carbon dioxide and oxygen on microbial secondary metabolite producers and the maintenance of these two parameters at optimal levels have been studied extensively. Nevertheless, most studies have focussed on their influence on specific product formation and condition optimization of established processes. Considerably less attention has been paid to the influence of reduced or elevated carbon dioxide and oxygen levels on the overall metabolite profiles of the investigated organisms. The synergistic action of both gases has garnered even less attention.ResultsWe show that the composition of the gas phase is highly important for the production of different metabolites and present a simple approach that enables the maintenance of defined concentrations of both O2 and CO2 during bioprocesses over broad concentration ranges with a minimal instrumental setup by using endogenously produced CO2. The metabolite profiles of a myxobacterium belonging to the genus Chondromyces grown under various concentrations of CO2 and O2 showed considerable differences. Production of two unknown, highly cytotoxic compounds and one antimicrobial substance was found to increase depending on the gas composition. In addition, the observation of CO2 and O2 in the exhaust gas allowed optimization and control of production processes.ConclusionsMyxobacteria are becoming increasingly important due to their potential for bioactive secondary metabolite production. Our studies show that the influence of different gas partial pressures should not be underestimated during screening processes for novel compounds and that our described method provides a simple tool to investigate this question.

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Section: Resultssupporting

confidence: 59%

Methods to optimize myxobacterial fermentations using off-gas analysis

Hüttel

Müller

2012

Microb Cell Fact

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“…Only in some cases pCO 2 has been measured in the exhaust gas. This is important since there exists a complex relationship between dCO 2 and CO 2 in the gas phase that cannot be easily predicted, as both variables can constantly vary in a culture due to changes in specific and overall oxygen uptake rate, as well as operational changes in gas flow rate, agitation rate, and total pressure, among others (Dahod 1993;El-Sabbagh et al, 2006;McIntyre and McNeil, 1997). To overcome the limitations of studies reported to date, in the present work the effect of CO 2 was determined in batch cultures of recombinant E. coli by continuously measuring dCO 2 online and controlling it at constant values.…”

Section: Introductionmentioning

confidence: 99%

Metabolic and transcriptional response of recombinant Escherichia coli to elevated dissolved carbon dioxide concentrations

Baez

Flores

Bolívar

et al. 2009

Biotech & Bioengineering

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The effect of dissolved carbon dioxide (dCO(2)) concentration on the stoichiometric and kinetic constants and by-product accumulation was determined for Escherichia coli cells producing recombinant green fluorescent protein (GFP). Constant dCO(2), in the range of 20-300 mbar, was maintained during batch cultures by manipulating the inlet gas composition. As dCO(2) increased, specific growth rate (micro) decreased, and acetate accumulation and the time for onset of GFP production increased. Maximum biomass yield on glucose and GFP concentration were affected for dCO(2) above 70 and 150 mbar, respectively. Expression analysis of 16 representative genes showed that E. coli can respond at the transcriptional level upon exposure to increasing dCO(2), and revealed possible mechanisms responsible for the detrimental effects of high dCO(2). Genes studied included those involved in decarboxylation reactions (aceF, icdA, lpdA, sucA, sucB), genes from pathways of production and consumption of acetate (ackA, poxB, acs, aceA, fadR), genes from gluconeogenic and anaplerotic metabolism (pckA, ppc), genes from the acid resistance (AR) systems (adiA, gadA, gadC), and the heterologous gene (gfp). The transcription levels of tricarboxylic acid (TCA) cycle genes (icdA, sucA, sucB) and glyoxylate shunt (aceA) decreased as dCO(2) increased, whereas fadR (that codes for a negative regulator of the glyoxylate operon) and poxB (that codes for PoxB which is involved in acetate production from pyruvate) were up-regulated as dCO(2) increased up to 150 mbar. Furthermore, transcription levels of genes from the AR systems increased as dCO(2) increased up to 150 mbar, indicating that elevated dCO(2) triggers an acid stress response in E. coli cells. Altogether, such results suggest that the increased acetate accumulation and reduction in mu, biomass yield and maximum GFP concentration under high dCO(2) resulted from a lower carbon flux to TCA cycle, the concomitant accumulation of acetyl-CoA or pyruvate, and the acidification of the cytoplasm.

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“…Aeration provides oxygen as well as strips CO 2 and often ammonia (Roman and Gavrilescu,1994), eliminating two potential inhibitors of secondary metabolism. Production rate suppression has been caused specifically by dCO 2 levels rising above a threshold value (Dahod,1993). For example, there was a linear streptomycin titer decline at 140 h for dCO 2 levels above 8 mL/100 mL within the first 50 h of fermentation (Bylinkina and Birukov,1972).…”

Section: Resultsmentioning

confidence: 99%

Actinomycetes scale‐up for the production of the antibacterial, nocathiacin

Junker

Walker

Hesse

et al. 2009

Biotechnology Progress

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An Amycolatopsis fastidiosa culture, which produces the nocathiacin class of antibacterial compounds, was scaled up to the 15,000 L working volume. Lower volume pilot fermentations (600, 900, and 1,500 L scale) were conducted to determine process feasibility at the 15,000 L scale. The effects of inoculum volume, impeller tip speed, volumetric gas flow rate, superficial gas velocity, backpressure, and sterilization heat stress were examined to determine optimal scale-up operating conditions. Inoculum volume (6 vs. 2 vol %) and medium sterilization (R(o) of 68 vs. 92 min(-1)) had no effect on productivity or titer, and higher impeller tip speeds (2.1 vs. 2.9 m/s) had a slight effect (20% decrease). In contrast, higher backpressure, incorporating increased head pressure at the 15,000 L scale (1.2 vs. 0.7 kg/cm(2)) and low gas flow rates (0.25 vs. 0.8 vvm), appeared to be problematic (40-50% decrease). High off-gas CO2 levels were likely reasons for observed lower productivity. Consequently, air flow rate for this 25-fold scale-up (600-15,000 L) was controlled to match off-gas CO2 profiles of acceptable smaller scale batches to maintain levels below 0.5%. The 15,000 L-scale fermentation achieved an expected nocathiacin I titer of 310 mg/L after 7 days. Other on-line data (i.e., pH, oxygen uptake rate, and CO2 evolution rate) and off-line data (i.e., analog production, glucose utilization, ammonium production, and dry cell weight) at the 15,000 L scale also tracked similarly to the smaller scale, demonstrating successful fermentation scale-up.

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Dissolved Carbon Dioxide Measurement and Its Correlation with Operating Parameters in Fermentation Processes

Cited by 24 publications

References 9 publications

Methods to optimize myxobacterial fermentations using off-gas analysis

Methods to optimize myxobacterial fermentations using off-gas analysis

Metabolic and transcriptional response of recombinant Escherichia coli to elevated dissolved carbon dioxide concentrations

Actinomycetes scale‐up for the production of the antibacterial, nocathiacin

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