Process Engineering Aspects for the Microbial Conversion of C1 Gases

Weuster‐Botz, Dirk

doi:10.1007/10_2021_172

Cited by 3 publications

(3 citation statements)

References 85 publications

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“…Syngas fermentation on an industrial scale is performed in bubble column or gaslift reactors [53,60]. The utilization of bubble columns instead of stirred-tank reactors is important due to the lower power input and more efficient syngas conversion at high liquid heights [61]. In an industrial scale stirred-tank bioreactor, the power input by the stirrer to increase the gas-liquid mass transfer rates is typically the main expense factor of the operating costs.…”

Section: Challenges and Opportunities On High Syngas Conversion In In...mentioning

confidence: 99%

“…The detailed gas composition of the biogenic syngas could be adjusted to allow for a better ratio of the individual gas components and, thus, a higher conversion of the syngas components. Additionally, future research could apply pilot scale bubble column bioreactors to mimic more closely the conditions in an industrially applied syngas fermentation process [61]. Syngas fermentation remains a promising technology for the production of fuels and platform chemicals from renewable sources by using acetogenic microorganisms.…”

Section: Outlook On Future Syngas Fermentation Researchmentioning

confidence: 99%

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Conversion of Syngas from Entrained Flow Gasification of Biogenic Residues with Clostridium carboxidivorans and Clostridium autoethanogenum

et al. 2022

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Synthesis gas fermentation is a microbial process, which uses anaerobic bacteria to convert CO-rich gases to organic acids and alcohols and thus presents a promising technology for the sustainable production of fuels and platform chemicals from renewable sources. Clostridium carboxidivorans and Clostridium autoethanogenum are two acetogenic bacteria, which have shown their high potential for these processes by their high tolerance toward CO and in the production of industrially relevant products such as ethanol, 1-butanol, 1-hexanol, and 2,3-butanediol. A promising approach is the coupling of gasification of biogenic residues with a syngas fermentation process. This study investigated batch processes with C. carboxidivorans and C. autoethanogenum in fully controlled stirred-tank bioreactors and continuous gassing with biogenic syngas produced by an autothermal entrained flow gasifier on a pilot scale >1200 °C. They were then compared to the results of artificial gas mixtures of pure gases. Because the biogenic syngas contained 2459 ppm O2 from the bottling process after gasification of torrefied wood and subsequent syngas cleaning for reducing CH4, NH3, H2S, NOX, and HCN concentrations, the oxygen in the syngas was reduced to 259 ppm O2 with a Pd catalyst before entering the bioreactor. The batch process performance of C. carboxidivorans in a stirred-tank bioreactor with continuous gassing of purified biogenic syngas was identical to an artificial syngas mixture of the pure gases CO, CO2, H2, and N2 within the estimation error. The alcohol production by C. autoethanogenum was even improved with the purified biogenic syngas compared to reference batch processes with the corresponding artificial syngas mixture. Both acetogens have proven their potential for successful fermentation processes with biogenic syngas, but full carbon conversion to ethanol is challenging with the investigated biogenic syngas.

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Section: Challenges and Opportunities On High Syngas Conversion In In...mentioning

confidence: 99%

Section: Outlook On Future Syngas Fermentation Researchmentioning

confidence: 99%

Conversion of Syngas from Entrained Flow Gasification of Biogenic Residues with Clostridium carboxidivorans and Clostridium autoethanogenum

et al. 2022

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“…However, the challenges in syngas fermentation remain the low solubilities of H 2 and CO in water, which may result in gas-liquid mass transfer limitations, the poor alcohol-to-acid ratios and low product concentrations with wild-type strains, and the low biomass densities in submerged syngas fermentation resulting in low volumetric productivities [27]. Therefore, various studies have investigated the optimization of autotrophic cultivation conditions, including partial pressures of the syngas components (nutrient level), pressure, pH, medium composition, and temperature [4,14,28,29].…”

Section: Introductionmentioning

confidence: 99%

Mixotrophic Syngas Conversion Enables the Production of meso-2,3-butanediol with Clostridium autoethanogenum

Oppelt,

Rückel,

Rupp

et al. 2024

Fermentation

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Providing simultaneously autotrophic and heterotrophic carbon sources is a promising strategy to overcome the limits of autotrophic syngas fermentations. D-xylose and L-arabinose are particularly interesting as they can be obtained by the hydrolysis of lignocellulosic biomass. The individual conversion of varying initial concentrations of these pentoses and D-fructose as reference was studied with C. autoethanogenum in fully controlled stirred-tank reactors with a continuous syngas supply. All mixotrophic batch processes showed increased biomass and product formation compared to an autotrophic reference process. Simultaneous CO and D-xylose or L-arabinose conversion was observed in contrast to D-fructose. In the mixotrophic batch processes with L-arabinose or D-xylose, the simultaneous CO and sugar conversion resulted in high final alcohol-to-acid ratios of up to 58 g g−1. L-arabinose was superior as a mixotrophic carbon source because biomass and alcohol concentrations (ethanol and 2,3-butanediol) were highest, and significant amounts of meso-2,3-butanediol (>1 g L−1) in addition to D-2,3-butanediol (>2 g L−1) were solely produced with L-arabinose. Furthermore, C. autoethanogenum could not produce meso-2,3 butanediol under purely heterotrophic conditions. The mixotrophic production of meso-2,3-butanediol from L-arabinose and syngas, both available from residual lignocellulosic biomass, is very promising for use as a monomer for bio-based polyurethanes or as an antiseptic agent.

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Continuous Production of Ethanol, 1-Butanol and 1-Hexanol from CO with a Synthetic Co-Culture of Clostridia Applying a Cascade of Stirred-Tank Bioreactors

et al. 2023

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Syngas fermentation with clostridial co-cultures is promising for the conversion of CO to alcohols. A CO sensitivity study with Clostridium kluyveri monocultures in batch operated stirred-tank bioreactors revealed total growth inhibition of C. kluyveri already at 100 mbar CO, but stable biomass concentrations and ongoing chain elongation at 800 mbar CO. On/off-gassing with CO indicated a reversible inhibition of C. kluyveri. A continuous supply of sulfide led to increased autotrophic growth and ethanol formation by Clostridium carboxidivorans even at unfavorable low CO concentrations. Based on these results, a continuously operated cascade of two stirred-tank reactors was established with a synthetic co-culture of both Clostridia. An amount of 100 mbar CO and additional sulfide supply enabled growth and chain elongation in the first bioreactor, whereas 800 mbar CO resulted in an efficient reduction of organic acids and de-novo synthesis of C2-C6 alcohols in the second reactor. High alcohol/acid ratios of 4.5–9.1 (w/w) were achieved in the steady state of the cascade process, and the space-time yields of the alcohols produced were improved by factors of 1.9–5.3 compared to a batch process. Further improvement of continuous production of medium chain alcohols from CO may be possible by applying less CO-sensitive chain-elongating bacteria in co-cultures.

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Process Engineering Aspects for the Microbial Conversion of C1 Gases

Cited by 3 publications

References 85 publications

Conversion of Syngas from Entrained Flow Gasification of Biogenic Residues with Clostridium carboxidivorans and Clostridium autoethanogenum

Conversion of Syngas from Entrained Flow Gasification of Biogenic Residues with Clostridium carboxidivorans and Clostridium autoethanogenum

Mixotrophic Syngas Conversion Enables the Production of meso-2,3-butanediol with Clostridium autoethanogenum

Continuous Production of Ethanol, 1-Butanol and 1-Hexanol from CO with a Synthetic Co-Culture of Clostridia Applying a Cascade of Stirred-Tank Bioreactors

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