Options for biochemical production of 4‐hydroxybutyrate and its lactone as a substitute for petrochemical production

Efe, C.; Straathof, Adrie J. J.; Wielen, Luuk A.M. van der

doi:10.1002/bit.21709

Cited by 21 publications

(6 citation statements)

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“…In fact, this could be the reason why the alternative respiratory pathway as well as uncoupling proteins (UCPs; Pu et al, 2015) become more prominent under stress conditions, when additional energy has to be allocated specifically to the plasma membrane. The second mechanism of H + consumption by decarboxylation of glutamate is also energetically downhill; Efe et al (2008) calculated a free energy release of À35 to À17 kJ mol À1 , depending on the actual concentrations. It has to be stressed again that additional energy is required to balance the charge influx associated with H + uptake, either by release of previously accumulated K + stored in the vacuole, serving as a kind of 'battery' for plasma membrane transport, or by channelmediated anion uptake (provided that anion concentrations are higher outside than inside the cell to overcome the negative membrane potential).…”

Section: The Biochemical Ph Clamp: Thermodynamic and Energetic Aspectsmentioning

confidence: 99%

Biochemical pH clamp: the forgotten resource in membrane bioenergetics

Wegner

Shabala

2019

New Phytologist

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Summary Solute uptake and release by plant cells are frequently energized by coupling to H+ influx supported by the proton motive force (pmf). The pmf results from a stable pH difference between the apoplast and the cytosol, with bulk values ranging from 4.9 to 5.8 and from 7.1 to 7.5, respectively, in combination with a negative electrical membrane potential. The P‐type H+ ATPases pumping H+ from the cytosol into the apoplast at the expense of ATP hydrolysis are generally viewed as the only pmf source, exclusively linking membrane transport to energy metabolism. However, recent evidence suggests that pump activity may be insufficient to energize transport, particularly under stress conditions. Indeed, cytosolic H+ scavenging and apoplastic H+ generation by metabolism (denoted as ‘active’ buffering in contrast to the readily exhausted ‘passive’ matrix buffering) also stabilize the pH gradient. In the cytosol, H+ scavenging is mainly associated with malate decarboxylation catalyzed by malic enzyme, and via the GABA shunt of the tricarboxylic acid (TCA) cycle involving glutamate decarboxylation. In the apoplast, formation of bicarbonate from CO2, the end‐product of respiration, generates H+ at pH ≥ 6. Membrane potential is stabilized by K+ release and/or by anion uptake via ion channels. Finally, thermodynamic aspects of active buffering are discussed.

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Section: The Biochemical Ph Clamp: Thermodynamic and Energetic Aspectsmentioning

confidence: 99%

Biochemical pH clamp: the forgotten resource in membrane bioenergetics

Wegner

Shabala

2019

New Phytologist

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“…Unfortunately, the large majority of the available equilibrium constants available in the literature are the apparent values. These apparent values (or sometimes Debye–Hückel corrected equilibrium constants) have frequently been used to describe metabolic pathways. − In metabolic pathways, the concentrations of the reacting agents are usually very low, so in this case, the apparent equilibrium constants and the thermodynamic equilibrium constants may indeed be similar, justifying such an approach. However, in vitro reaction concentrations can be significantly higher.…”

Section: Introductionmentioning

confidence: 99%

Reaction Equilibrium of the ω-Transamination of (S)-Phenylethylamine: Experiments and ePC-SAFT Modeling

Voges

Abu

Gundersen

et al. 2017

Org. Process Res. Dev.

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This work focuses on the thermodynamic equilibrium of the ω-transaminase-catalyzed reaction of (S)phenylethylamine with cyclohexanone to acetophenone and cyclohexylamine in aqueous solution. For this purpose, the equilibrium concentrations of the reaction were experimentally investigated under varying reaction conditions. It was observed that the temperature (30 and 37 °C), the pH (between pH 7 and pH 9), as well as the initial reactant concentrations (between 5 and 50 mmol•kg −1 ) influenced the equilibrium position of the reaction. The position of the reaction equilibrium was moderately shifted toward the product side by either decreasing temperature or decreasing pH. In contrast, the initial ratio of the reactants showed only a marginal influence on the equilibrium position. Further experiments showed that increasing the initial reactant concentrations significantly shifted the equilibrium position to the reactant side. In order to explain these effects, the activity coefficients of the reacting agents were calculated and the activity-based thermodynamic equilibrium constant K th of the reaction was determined. For this purpose, the activity coefficients of the reacting agents were modeled at their respective experimental equilibrium concentrations using the equation of state electrolyte PC-SAFT (ePC-SAFT). The combination of the concentrations of the reacting agents at equilibrium and their respective activity coefficients provided the thermodynamically consistent equilibrium constant K th . Unexpectedly, the experimental K m values deviated by a factor of up to four from the thermodynamic equilibrium constant K th . The observed concentration dependency of the experimental K m values could be explained by the influence of concentration on activity coefficients. Further, these activity coefficients were found to be strongly temperature dependent, which is important for the determination of standard enthalpy of reactions, which in this work was found to be +7.7 ± 2.8 kJ•mol −1 . Using the so-determined K th and activity coefficients of the reacting agents (ePC-SAFT), the equilibrium concentrations of the reaction were predicted for varying initial reactant concentrations, which were found to be in good agreement with the experimental behavior. These results showed a non-negligible influence of the activity coefficients of the reacting agents on the equilibrium position and, thus, on the product yield. Experiments and ePC-SAFT predictions showed that the equilibrium position can only be described accurately by taking activity coefficients into account.

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“…Enzymatic synthesis of γ-butyrolactone has been explored using lactonization of 4-hydroxybutyrate, which itself might be obtained by fermentation (Figure ) …”

Section: Esters and Lactonesmentioning

confidence: 99%

“…362 Enzymatic synthesis of γ-butyrolactone has been explored using lactonization of 4-hydroxybutyrate, which itself might be obtained by fermentation (Figure 11). 363 C. antarctica Lipase B showed good lactonization rates, but this requires a low pH, and therefore, it was argued that it cannot be used in vivo. However, the next section shows a solution to this problem for a related compound.…”

Section: Fatty Acid (M)ethyl Estersmentioning

confidence: 99%