Modelling the aerobic degradation of toluene in a closed chemostat with and without a head space outlet

Löser, Christian; Ray, P.

doi:10.1002/abio.370140408

Cited by 4 publications

(2 citation statements)

References 3 publications

(1 reference statement)

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“…In this equation, C&Is03N is the substrate 4-nitrophenol and C5H802N denotes the biomass [24]. For simplification all components were considered to be undissociated.…”

Section: Stoichiometry During Growth Of Pseudomonas Putida Pnpimentioning

confidence: 99%

Growth kinetics of the 4‐nitrophenol degrading strain Pseudomonas putida PNP1

Löser

Oubelli

Hertel

1998

Acta Biotechnologica

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A Cnitrophenol degrading strain PNPl isolated from the El-Harrach River near Algiers (Algeria) was studied with respect to its growth behaviour. According to the morphological and biochemical characteristics this strain was assigned to Pseudomom putiah. Besides 4-nitrophenol, the strain also used 1.2-and 1,4-dihydroxybenzene, benzoate, 4-hydroxybenzoate and 3&dihydroxybenmate as sources of carbon and energy, degrading them exclusively via the ortho pathway. Pseudomom putidn PNPl degrades 4-nitrophenol through a purely oxidative pathway with release of the nitro group as nitrite. During cultivation with 4-nitrophenol in ammonium-containing mineral medium. the strain PNPl grew optimally at pH 7 and at a temperature between 30 and 35 "C and showed stoichiometric nitrite release (at pH 7 and 30 "C MONOD model parameters hax = 0.615 h -1 and Ks = 0.145 mg/l). A phenomenological model for the description of growth inhibition at high 4-nitrophenol concentrations was derived (below 400 mg/l only weak inhibition and at 600 mg/l acute toxicity). In ammonium-free medium, the maximum specific growth rate was reduced to 0.318 h -1 and part of the 4-nitrophenol-N was used as the nitrogen source (32% N in biomass and 68% N in nitrite). The yield coefficients of strain PNPl were smaller in ammonium-free than in ammoniumcontaining medium (e.g. with 4-nitrophenol Y x /~ = 0.305 glg compared to 0.350 &), which can be explained by the energy expense for the assimilatory nitrite reduction in the biosynthesis of N-containing cellular compounds. But the oxygen consumption was only slightly influenced by the ammonium content of the cultivation medium (e.g. with 4-nitrophenol Y m = 1.005 g/g compared to 0.954 g/g). IntroducionNitroaromatic compounds are widely distributed substances in the chemistry and processing industries as they are of great importance in the production of synthetic dyes, pesticides, pharmaceutical raw materials and photochemicals [ 11. Because of their high mutagenic and cancerogenic potential, nitroaromatic substances pose a dan-

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“…In this equation, C&Is03N is the substrate 4-nitrophenol and C5H802N denotes the biomass [24]. For simplification all components were considered to be undissociated.…”

Section: Stoichiometry During Growth Of Pseudomonas Putida Pnpimentioning

confidence: 99%

Growth kinetics of the 4‐nitrophenol degrading strain Pseudomonas putida PNP1

Löser

Oubelli

Hertel

1998

Acta Biotechnologica

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“…At intensive stirring, the

k_{V O C, L} a

value is distinctly larger than the

F_{G, R}

V_{L}

‐

K_{V O C, L / G}

ratio so that the

1 / k_{V O C, L} a

term in Equation () becomes negligible, resulting in a simplified equation:

\begin{matrix} true \\ right \frac{d C_{VOC, L}}{d t} & = & left R_{VOC} - C_{VOC, L} \cdot \frac{1 - β_{VOC}}{K_{VOC, L / G}} \cdot \frac{F_{G, R}}{V_{L}} \\ left normalat k_{VOC, L} a ≫ \frac{F_{G, R} / V_{L}}{K_{VOC, L / G}} \end{matrix}

Stripping experiments clearly demonstrated that this simplification is permissible at least for ethyl acetate and ethanol even if the stirring speed is as low as 100 rpm [19]. For substances with a low partition coefficient such as styrene [40] and toluene [60], this simplification is not applicable.…”

Section: Resultsmentioning

confidence: 99%

A new approach for balancing the microbial synthesis of ethyl acetate and other volatile metabolites during aerobic bioreactor cultivations

Löser

Kupsch

Walther

et al. 2020

Engineering in Life Sciences

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Ethyl acetate is an organic solvent with many industrial applications, currently produced by energy‐intensive chemical processes based on fossil carbon resources. Ethyl acetate can be synthesized from renewable sugars by yeasts like Kluyveromyces marxianus in aerobic processes. However, ethyl acetate is highly volatile and thus stripped from aerated cultivation systems which complicate the quantification of the produced ester. Synthesis of volatile metabolites is commonly monitored by repeated analysis of metabolite concentrations in both the gas and liquid phase. In this study, a model‐based method for quantifying the synthesis and degradation of volatile metabolites was developed. This quantification of volatiles is solely based on repeatedly measured gas‐phase concentrations and allows calculation of reaction rates and yields in high temporal resolution. Parameters required for these calculations were determined in abiotic stripping tests. The developed method was validated for ethyl acetate, ethanol and acetaldehyde which were synthesized by K. marxianus DSM 5422 during an iron‐limited batch cultivation; it was shown that the presented method is more precise and less time‐consuming than the conventional method. The biomass‐specific synthesis rate and the yield of ethyl acetate varied over time and exhibited distinct momentary maxima of 0.50 g g‒1h‒1 and 0.38 g g‒1 at moderate iron limitation.

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Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrations

Alagappan

Cowan

2001

Biotech & Bioengineering

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This paper reintroduces the Wayman and Tseng model for representing substrate inhibition effects on specific growth rate by further documenting its potential predictive capabilities. It also introduces a modification to this model in which an Andrews inhibition function is used in place of the Monod noninhibitory substrate function. This modification better represents the relationship between specific growth rate and substrate concentration for those substrates that show Andrews type inhibition at lower substrate concentrations, rather than the Monod type noninhibitory behavior described in the model of Wayman and Tseng. Results from nonlinear, least squares regression analysis are used to evaluate the ability of these models to empirically represent experimental data (both new and from the literature). The statistical goodness of fit is evaluated by comparing the regression results against those obtained using other empirical models. Finally, possible mechanisms of toxicity responsible for the observed inhibition trends are used to further justify use of these empirical models. The dominant mechanism considered to be relevant for conceptually explaining complete inhibition at high concentrations of solvents is the deterioration of cell membrane integrity. Literature citations are used to support this argument. This work should lead to improvements in the mathematical modeling of contaminant fate and transport in the environment and in the simulation of microbial growth and organic compound biodegradation in engineered systems.

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Modelling the aerobic degradation of toluene in a closed chemostat with and without a head space outlet

Cited by 4 publications

References 3 publications

Growth kinetics of the 4‐nitrophenol degrading strain Pseudomonas putida PNP1

Growth kinetics of the 4‐nitrophenol degrading strain Pseudomonas putida PNP1

A new approach for balancing the microbial synthesis of ethyl acetate and other volatile metabolites during aerobic bioreactor cultivations

Biokinetic models for representing the complete inhibition of microbial activity at high substrate concentrations

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