Alleviating mass transfer limitations in industrial external-loop syngas-to-ethanol fermentation

Puiman, Lars; Abrahamson, Britt; Lans, R. G. J. M. van der; Haringa, Cees; Noorman, Henk; Picioreanu, Cristian

doi:10.1016/j.ces.2022.117770

Cited by 16 publications

(20 citation statements)

References 72 publications

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“…As a starting point for the simulations, the 3D reactor geometry and computed flow field of the EL-GLR were used, for which the modelling approach was validated on pilotscale data, as described in [4]. The only change was in the syngas composition, from a 50% CO, 50% N 2 mixture to a 50% CO, 20% H 2 , 30% CO 2 (v/v) mixture [29].…”

Section: Geometry and Flow Fieldmentioning

confidence: 99%

“…The company LanzaTech successfully commercializes the fermentation of synthesis gas (containing CO, H 2 and CO 2 ) into ethanol, and is currently exploring other products, such as acetone and isopropanol [3]. Although mass transfer limitations have often been accounted as a limiting factor for scale-up of syngas fermentation, such limitations could highly relieved greatly by making products which are bubble coalescence-suppressing, such as ethanol [4].…”

Section: Introductionmentioning

confidence: 99%

“…Usually substrate gradients occur when the characteristic time of reaction τ rxn is significantly lower than the characteristic time of transport, which is related to mixing for substrates in the liquid phase via the circulation time (t c ), and to mass transfer for gaseous-phase substrates (τ MT ) [10,11]. For large-scale syngas fermentation, τ rxn is expected to be much lower (~0.3 s; [12]) than τ MT (around 10-20 s; [4]) and t c (~40 s; Figure S1). Furthermore, both hydrostatic pressure differences (3.5 bar at the bottom vs. 1 bar near the headspace) and gas mole fraction differences (e.g., y CO decreases from 50% to 5% from bottom to top due to consumption) cause a gradient of around factor 35 in saturation concentration, while the volumetric mass transfer coefficient k L a might vary locally due to turbulent fluctuations, differences in bubble size and gas hold-up [4].…”

Section: Introductionmentioning

confidence: 99%

“…For large-scale syngas fermentation, τ rxn is expected to be much lower (~0.3 s; [12]) than τ MT (around 10-20 s; [4]) and t c (~40 s; Figure S1). Furthermore, both hydrostatic pressure differences (3.5 bar at the bottom vs. 1 bar near the headspace) and gas mole fraction differences (e.g., y CO decreases from 50% to 5% from bottom to top due to consumption) cause a gradient of around factor 35 in saturation concentration, while the volumetric mass transfer coefficient k L a might vary locally due to turbulent fluctuations, differences in bubble size and gas hold-up [4]. We hypothesize that all of this leads to sizeable dissolved CO and H 2 concentration gradients, which might have implications for the syngas fermentation performance.…”

Section: Introductionmentioning

confidence: 99%

“…The impact of gas (CO 2 ) production on the dissolved gas concentration gradients, and thus possible fluctuations for the microbe, was studied. We used our previous CFD model of an industrial-scale external-loop gas-lift reactor (EL-GLR) and our lab observations to develop and analyses lifelines representative for large-scale syngas fermentation [4,31].…”

Section: Introductionmentioning

confidence: 99%

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Downscaling Industrial-Scale Syngas Fermentation to Simulate Frequent and Irregular Dissolved Gas Concentration Shocks

et al. 2023

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In large-scale syngas fermentation, strong gradients in dissolved gas (CO, H2) concentrations are very likely to occur due to locally varying mass transfer and convection rates. Using Euler-Lagrangian CFD simulations, we analyzed these gradients in an industrial-scale external-loop gas-lift reactor (EL-GLR) for a wide range of biomass concentrations, considering CO inhibition for both CO and H2 uptake. Lifeline analyses showed that micro-organisms are likely to experience frequent (5 to 30 s) oscillations in dissolved gas concentrations with one order of magnitude. From the lifeline analyses, we developed a conceptual scale-down simulator (stirred-tank reactor with varying stirrer speed) to replicate industrial-scale environmental fluctuations at bench scale. The configuration of the scale-down simulator can be adjusted to match a broad range of environmental fluctuations. Our results suggest a preference for industrial operation at high biomass concentrations, as this would strongly reduce inhibitory effects, provide operational flexibility and enhance the product yield. The peaks in dissolved gas concentration were hypothesized to increase the syngas-to-ethanol yield due to the fast uptake mechanisms in C. autoethanogenum. The proposed scale-down simulator can be used to validate such results and to obtain data for parametrizing lumped kinetic metabolic models that describe such short-term responses.

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Section: Geometry and Flow Fieldmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Downscaling Industrial-Scale Syngas Fermentation to Simulate Frequent and Irregular Dissolved Gas Concentration Shocks

et al. 2023

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A novel experimental method to determine substrate uptake kinetics of gaseous substrates applied to the carbon monoxide‐fermenting Clostridium autoethanogenum

Allaart,

Korkontzelos,

Sousa

et al. 2024

Biotech & Bioengineering

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Syngas fermentation has gained momentum over the last decades. The cost‐efficient design of industrial‐scale bioprocesses is highly dependent on quantitative microbial growth data. Kinetic and stoichiometric models for syngas‐converting microbes exist, but accurate experimental validation of the derived parameters is lacking. Here, we describe a novel experimental approach for measuring substrate uptake kinetics of gas‐fermenting microbes using the model microorganism Clostridium autoethanogenum. One‐hour disturbances of a steady‐state chemostat bioreactor with increased CO partial pressures (up to 1.2 bar) allowed for measurement of biomass‐specific CO uptake‐ and CO2 production rates (, ) using off‐gas analysis. At a pCO of 1.2 bar, a of −119 ± 1 mmol g−1X h−1 was measured. This value is 1.8–3.5‐fold higher than previously reported experimental and kinetic modeling results for syngas fermenters. Analysis of the catabolic flux distribution reveals a metabolic shift towards ethanol production at the expense of acetate at pCO 0.6 atm, likely to be mediated by acetate availability and cellular redox state. We characterized this metabolic shift as acetogenic overflow metabolism. These results provide key mechanistic understanding of the factors steering the product spectrum of CO fermentation in C. autoethanogenum and emphasize the importance of dedicated experimental validation of kinetic parameters.

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Challenges and prospects of microbial α-amylases for industrial application: a review

Ashok,

Dasgupta,

Ray

et al. 2023

World J Microbiol Biotechnol

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Alleviating mass transfer limitations in industrial external-loop syngas-to-ethanol fermentation

Cited by 16 publications

References 72 publications

Downscaling Industrial-Scale Syngas Fermentation to Simulate Frequent and Irregular Dissolved Gas Concentration Shocks

Downscaling Industrial-Scale Syngas Fermentation to Simulate Frequent and Irregular Dissolved Gas Concentration Shocks

A novel experimental method to determine substrate uptake kinetics of gaseous substrates applied to the carbon monoxide‐fermenting Clostridium autoethanogenum

Challenges and prospects of microbial α-amylases for industrial application: a review

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