Utility of culture redox potential for identifying metabolic state changes in Amino acid fermentation

Kwong, Simon C. W.; Rao, Govind

doi:10.1002/bit.260380912

Cited by 28 publications

(11 citation statements)

References 18 publications

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“…Upon examining the off-line data, we observed that this discrepancy occurred when threonine was depleted (Figure IC). At this time, amino acid production commences, and in some cases (depending on oxygen availability), lactate formation reaches a maximum (Kwong and Rao, 1991 characteristics of CRP and do not contain information from a complete fermentation to check the profiles of CRP and DO. Contrary to Oktyabr'skii's reports, we did not observe any discrepancy between CRP and DO during glucose depletion in our fermentation system.…”

Section: Resultsmentioning

confidence: 99%

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On‐Line Assessment of Metabolic Activities Based on Culture Redox Potential and Dissolved Oxygen Profiles During Aerobic Fermentation

Kwong

Randers

Rao

1992

Biotechnology Progress

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We report here on the utility of on-line culture redox potential and dissolved oxygen measurements to identify metabolic changes in fermentation by Corynebacterium glutamicum under aerobic conditions. Metabolic changes were identified by observing discrepancies in the profile of culture redox potential and dissolved oxygen. On the basis of these measurements, we can identify the end of the lag phase, threonine exhaustion, and glucose exhaustion during fermentation.

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Section: Resultsmentioning

confidence: 99%

“…Briefly, all fermentations were carried out with Corynebacterium glutamicum ATCC 14296 at pH 7.2 and 30 "C in 5-L BioFlo I11 fermentors as previously described (Kwong and Rao, 1991). Data acquisition was on a Macintosh I1 computer.…”

Section: Methodsmentioning

confidence: 99%

On‐Line Assessment of Metabolic Activities Based on Culture Redox Potential and Dissolved Oxygen Profiles During Aerobic Fermentation

Kwong

Randers

Rao

1992

Biotechnology Progress

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“…Kwong and Rao have shown that reducing conditions can increase productions of homoserine and lysine by Clostridium glutamicum (13). In the same way, for Clostridium acetobutylicum, a decrease from Ϫ300 to Ϫ370 mV increases the production level of butanol and decreases those of butyrate and acetate (24).…”

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Extracellular Oxidoreduction Potential Modifies Carbon and Electron Flow in Escherichia coli

et al. 2000

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Wild-type Escherichia coli K-12 ferments glucose to a mixture of ethanol and acetic, lactic, formic, and succinic acids. In anoxic chemostat culture at four dilution rates and two different oxidoreduction potentials (ORP), this strain generated a spectrum of products which depended on ORP. Whatever the dilution rate tested, in low reducing conditions (؊100 mV), the production of formate, acetate, ethanol, and lactate was in molar proportions of approximately 2.5:1:1:0.3, and in high reducing conditions (؊320 mV), the production was in molar proportions of 2:0.6:1:2. The modification of metabolic fluxes was due to an ORP effect on the synthesis or stability of some fermentation enzymes; thus, in high reducing conditions, lactate dehydrogenasespecific activity increased by a factor of 3 to 6. Those modifications were concomitant with a threefold decrease in acetyl-coenzyme A (CoA) needed for biomass synthesis and a 0.5-to 5-fold decrease in formate flux. Calculations of carbon and cofactor balances have shown that fermentation was balanced and that extracellular ORP did not modify the oxidoreduction state of cofactors. From this, it was concluded that extracellular ORP could regulate both some specific enzyme activities and the acetyl-CoA needed for biomass synthesis, which modifies metabolic fluxes and ATP yield, leading to variation in biomass synthesis.A wealth of information is available on the response of Escherichia coli cellular metabolism to pH, water activity, or temperature variations, but little is known about the action of extracellular oxidoreduction potentials (ORP) on metabolism, although numerous reactions and regulations are of the oxidoreduction type. Previous studies have shown that substrates with different oxidation states yield a specific product spectrum. Thus, with glucose (oxidation state ϭ 0), the spectrum of main end products (formate:acetate:ethanol:lactate) is equal to 2:1:1:2, with glucitol (oxidation state ϭ Ϫ1), it is equal to 2:1:6:0.5, and with glucuronate (oxidation state ϭ 2), it is equal to 1:5:1:1, with small amounts of succinate also being produced in each case (1). Those metabolic flux modifications are also observed when the nature of external electron acceptors varies (7). In the same way, the NADH/NAD ϩ ratio, which is responsible for regulation of enzymes (8) or genes (16), can be influenced by the oxidation level of the substrate (36) or by the availability and nature of electron acceptors (7). In addition, protein folding and disulfide bond formation are regulated and modified by different oxidoreductase enzymes and oxidoreduction couples (glutathione, thioredoxin) (26). Recently, Taylor and Zhulin in their review have shown that ORP influences or could influence numerous regulations of cell functions controlled via Per-Arnt-Sim (PAS)-containing receptors (signaling modules that monitor changes in light, ORP, oxygen, and the overall energy level of a cell), transducers, and regulators (34). Thus, E. coli senses the medium ORP and swims to a preferred ORP niche by redox...

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“…Certain enzyme activities are controlled by ORP, and modification of this parameter can alter metabolic balances during anaerobic growth in Escherichia coli [8]. This is also true for the synthesis of coproporphyrine by E. coli [9], and the proportion of amino acid synthesized by Clostridium glutamicum [10]. In addition to the regulation of some metabolic pathways, ORP can regulate the expression of genes as shown for the FNR system of E. coli [11].…”

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Changes in the proton‐motive force in Escherichia coli in response to external oxidoreduction potential

Riondet

Cachon

Waché

et al. 1999

European Journal of Biochemistry

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The pH homeostasis and proton-motive force (Dp) of Escherichia coli are dependent on the surrounding oxidoreduction potential (ORP). Only the internal pH value and, thus, the membrane pH gradient (DpH) component of the Dp is modified, while the membrane potential (DC) does not change in a significant way. Under reducing conditions (E h , 50 mV at pH 7.0), E. coli decreases its Dp especially in acidic media (21% decrease at pH 7.0 and 48% at pH 5.0 for a 850-mV ORP decrease). Measurements of ATPase activity and membrane proton conductance (C H+ m ) depending on ORP and pH have shown that the internal pH decrease is due to an increase in membrane proton permeability without any modification of ATPase activity. We propose that low ORP values de-energize E. coli by modifying the thiol : disulfide balance of proteins, which leads to an increase in the membrane permeability to protons.Keywords: oxidoreduction potential; Escherichia coli; protomotive force; membrane potential; proton membrane conductance.Considerable efforts have been made to understand how cellular metabolism reacts to variations in pH, temperature, pressure and osmotic pressure (reviewed in [1]). However, little information is available on the response of microorganisms to changes in external oxidoreduction potential (ORP), although it is a pH interdependent parameter. Early studies suggested that each species or strain has a preferred redox potential range, within which growth is possible [2±4]. This physicochemical parameter also affects the heat resistance as demonstrated for various microorganisms [5±7]. Certain enzyme activities are controlled by ORP, and modification of this parameter can alter metabolic balances during anaerobic growth in Escherichia coli [8]. This is also true for the synthesis of coproporphyrine by E. coli [9], and the proportion of amino acid synthesized by Clostridium glutamicum [10]. In addition to the regulation of some metabolic pathways, ORP can regulate the expression of genes as shown for the FNR system of E. coli [11]. Recently, Bespalov et al.[12] have shown that E. coli can sense the medium's ORP and swim to a preferred ORP niche by means of redox taxis. This mechanism is consistent with a model in which a change in the proton-motive force (Dp) is the signal that triggers the behavioural response.In this paper, we report that medium's ORP modifies the generation of Dp in E. coli. Of the two parameters that compose Dp (membrane potential, DC, and difference in pH across the membrane, DpH), only DpH decreased when the ORP became more reducing, especially at acidic pH values. The transmembrane electrical potential remained constant. The ATPase activity was not ORP dependent, but that membrane proton conductance (C H+ m ) varied with ORP fluctuations. This deenergization of E. coli was essentially due to an increased membrane permeability to protons. This could be caused by a modification of the thiol : disulfide balance in membrane proteins linked to the medium's ORP. MATERIALS AND METHODSBacterial strains and cultur...

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Utility of culture redox potential for identifying metabolic state changes in Amino acid fermentation

Cited by 28 publications

References 18 publications

On‐Line Assessment of Metabolic Activities Based on Culture Redox Potential and Dissolved Oxygen Profiles During Aerobic Fermentation

On‐Line Assessment of Metabolic Activities Based on Culture Redox Potential and Dissolved Oxygen Profiles During Aerobic Fermentation

Extracellular Oxidoreduction Potential Modifies Carbon and Electron Flow in Escherichia coli

Changes in the proton‐motive force in Escherichia coli in response to external oxidoreduction potential

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