Side-by-Side Comparison of Clean and Biomass-Derived, Impurity-Containing Syngas as Substrate for Acetogenic Fermentation with Clostridium ljungdahlii

Infantes, Alba; Kugel, M.A.; Raffelt, Klaus; Neumann, Anke

doi:10.3390/fermentation6030084

Cited by 23 publications

(33 citation statements)

References 46 publications

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“…Rückel et al [50] found that NH 3 and H 2 S increased both growth and alcohol formation (ethanol, 1-butanol and 1-hexanol) during syngas fermentation by Clostridium carboxidivorans. On the other hand, Xu and Lewis [51] showed that NH 3 is rapidly converted to ammonium ion (NH 4 + ) in the fermentation media and the accumulated NH 4 + inhibits hydrogenase activity and cell growth of acetogenic bacteria. It seems that there is a microbial tolerance for these substances [10].…”

Section: Syngas Impuritiesmentioning

confidence: 99%

Impacts of Syngas Composition on Anaerobic Fermentation

et al. 2021

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Energy consumption places growing demands on modern lifestyles, which have direct impacts on the world’s natural environment. To attain the levels of sustainability required to avoid further consequences of changes in the climate, alternatives for sustainable production not only of energy but also materials and chemicals must be pursued. In this respect, syngas fermentation has recently attracted much attention, particularly from industries responsible for high levels of greenhouse gas emissions. Syngas can be obtained by thermochemical conversion of biomass, animal waste, coal, municipal solid wastes and other carbonaceous materials, and its composition depends on biomass properties and gasification conditions. It is defined as a gaseous mixture of CO and H2 but, depending on those parameters, it can also contain CO2, CH4 and secondary components, such as tar, oxygen and nitrogenous compounds. Even so, raw syngas can be used by anaerobic bacteria to produce biofuels (ethanol, butanol, etc.) and biochemicals (acetic acid, butyric acid, etc.). This review updates recent work on the influence of biomass properties and gasification parameters on syngas composition and details the influence of these secondary components and CO/H2 molar ratio on microbial metabolism and product formation. Moreover, the main challenges, opportunities and current developments in syngas fermentation are highlighted in this review.

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Section: Syngas Impuritiesmentioning

confidence: 99%

Impacts of Syngas Composition on Anaerobic Fermentation

et al. 2021

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“…Although studies have been performed that focused on the usage of real, biomass-derived synthesis gases, currently few studies have investigated the influences of the individual trace components to give further insight into the role of certain trace components (Datar et al, 2004;Ahmed et al, 2006;Xu et al, 2011;Infantes et al, 2020). The toxicity of HCN on the anaerobic bacteria C. ljungdahlii has already been analyzed and identified as a critical factor for the growth of anaerobic microorganisms with inhibiting effects at 1.6 mg L −1 and a strong toxic effect at concentrations of 0.065 g L −1 KCN in anaerobic shanking flasks (Oswald et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…This study aims to close the gap in the existing literature concerning the effects of individual trace impurities in syngases. Studies so far focused solely on the effects of syngas from gasification of biogenic residues and found inhibiting effects without clearly identifying the components responsible for the effects (Infantes et al, 2020;Liakakou et al, 2021). Also, most studies focused on C. ljungdahlii as a typical model organism for acetogenic bacteria, while this study used C. carboxidivorans as a promising acetogen for the production of longer chain alcohols.…”

Section: Introductionmentioning

confidence: 99%

Studies on Syngas Fermentation With Clostridium carboxidivorans in Stirred-Tank Reactors With Defined Gas Impurities

et al. 2021

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Syngas fermentation processes with acetogenic bacteria like Clostridium carboxidivorans have been proven to be a promising approach for the conversion of CO-rich waste gases into short- and medium-chain alcohols. The challenge of synthesis gas impurities, on the other hand, has always been a major concern for establishing an industrial-scale process, since some of the trace components in waste gases, such as NH3, H2S, and NOx, can have inhibiting or even toxic effects on microbial growth and product formation. Thus, this study aims to identify the effects of the main trace impurities in syngas from gasification of biogenic residues by the supply of defined concentrations of trace impurities to the cultivation medium. Autotrophic gas fermentation studies were performed with C. carboxidivorans in batch-operated fully-controlled stirred-tank bioreactors with continuous gas supply (80% CO and 20% CO2). The syngas components NH3 and H2S had a positive effect on both growth and alcohol formation (ethanol, 1-butanol, and 1-hexanol). The maximum biomass concentration was increased by more than 50%, and the maximum ethanol concentration was more than doubled with 5.0 g L−1 NH4Cl or 1.0 g L−1 H2S provided by the addition of 2.2 g L−1 thioacetamide. The addition of the nitrogen oxide species nitrate and nitrite, on the other hand, reduced biomass growth as well as alcohol concentrations. Already, the supply of 0.1 g L−1 NaNO3 resulted in reduced growth and 25% reduction of the maximum ethanol concentration. The production of the longer chain alcohols 1-butanol and 1-hexanol was reduced as well. All NaNO2 concentrations tested showed a strong toxic effect on the metabolism of C. carboxidivorans, and neither CO consumption nor product formation was observed after addition. As a consequence, NOx components in syngas from the gasification of biogenic residues should be reduced by the gasification process and/or selectively removed from the syngas after gasification.

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“…Contaminants such as tar, cyanide and other molecules are recognized as one of the biggest obstacles for direct syngas fermentation. These molecules can be present in concentrations shown to hinder microbial growth, significantly affecting overall yields and productivities [6][7][8][9][10][11][12][13][14]. For example, the presence of tar in crude syngas produced by lignin gasification was shown to induce cell dormancy and influence the redistribution of ethanol and acetic acid production by Clostridium carboxidivorans P7 T and Clostridium ragsdalei P11 [15,16].…”

Section: Introductionmentioning

confidence: 99%

“…For example, the presence of tar in crude syngas produced by lignin gasification was shown to induce cell dormancy and influence the redistribution of ethanol and acetic acid production by Clostridium carboxidivorans P7 T and Clostridium ragsdalei P11 [15,16]. Fortunately, some of these inhibitory effects may be mitigated by gradually adapting microbial cultures to crude syngas, prior to fermentation [9,10,17].…”

Section: Introductionmentioning

confidence: 99%

Lignin Syngas Bioconversion by Butyribacterium methylotrophicum: Advancing towards an Integrated Biorefinery

et al. 2021

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Hybrid bio-thermochemical based technologies have the potential to ensure greater feedstock flexibility for the production of bioenergy and bioproducts. This study focused on the bioconversion of syngas produced from low grade technical lignin to C2-/C4-carboxylic acids by Butyribacterium methylotrophicum. The effects of pH, medium supplementation and the use of crude syngas were analyzed. At pH 6.0, B. methylotrophicum consumed CO, CO2 and H2 simultaneously up to 87 mol% of carbon fixation, and the supplementation of the medium with acetate increased the production of butyrate by 6.3 times. In long-term bioreactor experiments, B. methylotrophicum produced 38.3 and 51.1 mM acetic acid and 0.7 and 2.0 mM butyric acid from synthetic and lignin syngas, respectively. Carbon fixation reached 83 and 88 mol%, respectively. The lignin syngas conversion rate decreased from 13.3 to 0.9 NmL/h throughout the assay. The appearance of a grayish pellet and cell aggregates after approximately 220 h was indicative of tar deposition. Nevertheless, the stressed cells remained metabolically active and maintained acetate and butyrate production from lignin syngas. The challenge that impurities represent in the bioconversion of crude syngas has a direct impact on syngas cleaning requirements and operation costs, supporting the pursuit for more robust and versatile acetogens.

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Side-by-Side Comparison of Clean and Biomass-Derived, Impurity-Containing Syngas as Substrate for Acetogenic Fermentation with Clostridium ljungdahlii

Cited by 23 publications

References 46 publications

Impacts of Syngas Composition on Anaerobic Fermentation

Impacts of Syngas Composition on Anaerobic Fermentation

Studies on Syngas Fermentation With Clostridium carboxidivorans in Stirred-Tank Reactors With Defined Gas Impurities

Lignin Syngas Bioconversion by Butyribacterium methylotrophicum: Advancing towards an Integrated Biorefinery

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