Enhanced alcohol titre and ratio in carbon monoxide-rich off-gas fermentation of Clostridium carboxidivorans through combination of trace metals optimization with variable-temperature cultivation

Shen, Shaohuang; Gu, Yang; Chai, Chaochao; Jiang, Weihong; Zhuang, Yingping; Wang, Yonghong

doi:10.1016/j.biortech.2017.04.099

Cited by 52 publications

(78 citation statements)

References 32 publications

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“…At higher hexanol concentrations, significant macroscopic flocculation of the cells was observed ( Figure 1C), indicating that hexanol has a negative effect on the cell membranes. Flocculation was also observed during fed-batch bottle fermentations after 3-4 days, and has been reported in other studies for the production of alcohols [19].…”

Section: The Acute Toxicity Of Hexanolsupporting

confidence: 83%

“…Extraction with oleyl alcohol showed promising detoxification results and increased the final hexanol titers by 2.5-fold. Our results therefore indicate a strong correlation between the inhibitory hexanol concentration of 10-12 mM and the highest hexanol titers of 13.3 mM produced by C. carboxidivorans P7 thus far [19]. Biocompatible extraction solvents such as oleyl alcohol remove toxic products from the fermentation broth and thus achieve higher overall titers.…”

Section: Discussionmentioning

confidence: 58%

“…Some acetogens, including C. carboxidivorans P7, can extend acetyl-CoA to synthesize the C4 products butyrate and butanol, and the C6 products caproate and hexanol [7,10]. The ability of C. carboxidivorans P7 to produce caproate and hexanol from syngas can be enhanced by medium and process optimization [10,19,20]. For example, the optimization of trace element composition significantly improved bacterial growth, leading to yields of 1.33 g/L (13.3 mM) hexanol [19].…”

Section: Introductionmentioning

confidence: 99%

“…The ability of C. carboxidivorans P7 to produce caproate and hexanol from syngas can be enhanced by medium and process optimization [10,19,20]. For example, the optimization of trace element composition significantly improved bacterial growth, leading to yields of 1.33 g/L (13.3 mM) hexanol [19]. Furthermore, a two-step fermentation process has been developed to overcome the limitations of biphasic growth, where most cell growth is restricted to acetogenesis and growth inhibition triggered by the switch to solventogenesis as the medium becomes more acidic.…”

Section: Introductionmentioning

confidence: 99%

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Hexanol biosynthesis from syngas by Clostridium carboxidivorans P7 is enhanced by in‑line extraction with a biocompatible solvent to avoid product toxicity

Kottenhahn¹,

Philipps²,

Jennewein³

2020

Preprint

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Background Clostridium carboxidivorans P7 has the rare ability to metabolize syngas – a mixture of H2, CO and CO2 – by converting it directly into industrially relevant alcohols (hexanol, butanol and ethanol) and the corresponding acids (caproate, butyrate and acetate). The product titers and ratios are highly dependent on the fermentation parameters and the composition of the syngas and growth medium. The hexanol titers produced by C. carboxidivorans P7 have recently been improved by optimizing these conditions, but little is known about the toxicity of hexanol towards Clostridium species. We hypothesized that the hexanol titers currently produced by C. carboxidivorans P7 are limited by product toxicity. Results We tested our hypothesis by exposing C. carboxidivorans P7 to different concentrations of hexanol and found that growth inhibition started at 10–12 mM, with an IC50 of 17.5 ± 1.6 mM. The presence of 20 mM hexanol was acutely toxic to C. carboxidivorans P7 as well as the model acetogen C. ljungdahlii, which does not produce hexanol. To avoid product toxicity, we added a biocompatible solvent (oleyl alcohol) to fed-batch bottle fermentations of C. carboxidivorans. This increased the total hexanol titers by 2.5-fold from 9.4 to 24.4 mM. Cell growth and product profiles in the aqueous phase after fermentation were similar in cultures with and without oleyl alcohol. The extraction phase contained high levels of hexanol (436 ± 101 mM) and butanol (100.3 ± 17.8 mM) as well as low levels of ethanol and traces of caproate. Conclusions Product toxicity was confirmed as a limiting factor during the conversion of syngas to hexanol by C. carboxidivorans P7. The addition of oleyl alcohol as a biocompatible solvent led to a significant increase in hexanol titers by facilitating the efficient and selective extraction of this product. We have therefore identified an in-line extraction strategy that increases the yield of hexanol and should allow for further improvements by genetic adaptation and/or process optimization.

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Section: The Acute Toxicity Of Hexanolsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Hexanol biosynthesis from syngas by Clostridium carboxidivorans P7 is enhanced by in‑line extraction with a biocompatible solvent to avoid product toxicity

Kottenhahn¹,

Philipps²,

Jennewein³

2020

Preprint

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“…A modification in the ATCC ® 1754 medium with MES as buffer was also reported, leading to 6.1 g/L of ethanol in a two stirred-tank bioreactor (in series) [21], without considering the high cost of MES. Enhancement of alcohol synthesis was reported using CO-rich off-gas fermentation by C. carboxidivorans by adding molybdenum/iron/cupper, aiming at the enzymes of the microorganism metabolism [22]. A final ethanol concentration of 3.5 g/L was obtained after 72 h of fermentation (approximately, 0.049 g/L•h) [19], the higher productivity found for this process in literature so far, but without considering the culture medium cost.…”

Section: Discussionmentioning

confidence: 97%

Experimental Design to Improve Cell Growth and Ethanol Production in Syngas Fermentation by Clostridium carboxidivorans

et al. 2020

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Fermentation of gases from biomass gasification, named syngas, is an important alternative process to obtain biofuels. Sequential experimental designs were used to increase cell growth and ethanol production during syngas fermentation by Clostridium carboxidivorans. Based on ATCC (American Type Culture Collection) 2713 medium composition, it was possible to propose a best medium composition for cell growth, herein called TYA (Tryptone-Yeast extract-Arginine) medium and another one for ethanol production herein called TPYGarg (Tryptone-Peptone-Yeast extract-Glucose-Arginine) medium. In comparison to ATCC® 2713 medium, TYA increased cell growth by 77%, reducing 47% in cost and TPYGarg increased ethanol production more than four-times, and the cost was reduced by 31%. In 72 h of syngas fermentation in TPYGarg medium, 1.75-g/L of cells, 2.28 g/L of ethanol, and 0.74 g/L of butanol were achieved, increasing productivity for syngas fermentation.

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Progress and development of syngas fermentation processes toward commercial bioethanol production

Owoade

Alshami

Levin

et al. 2023

Biofuels Bioprod Bioref

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Syngas is created through the thermochemical conversion of biomass using gasification or pyrolysis and from CO‐rich off‐gases obtained from industries such as steel mills. The Wood–Ljungdahl metabolic pathway, or one of its variations, is used by acetogenic bacteria to convert syngas components (CO, H2, and CO2) to alcohols and other compounds. Many factors affect how well syngas is fermented, including the bacteria species used, syngas composition, medium components, bioreactor type, operational parameters used and the gas–liquid mass transfer rate. These parameters impact carbon and electron flow in the bacteria, influencing the distribution, concentration and metabolic end‐product yield, which determines process feasibility. This article focuses on gas composition, microorganisms, gas–liquid mass transfer fermentation strategies, medium design and commercialization activities to develop the syngas fermentation processes.

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Enhanced alcohol titre and ratio in carbon monoxide-rich off-gas fermentation of Clostridium carboxidivorans through combination of trace metals optimization with variable-temperature cultivation

Cited by 52 publications

References 32 publications

Hexanol biosynthesis from syngas by Clostridium carboxidivorans P7 is enhanced by in‑line extraction with a biocompatible solvent to avoid product toxicity

Hexanol biosynthesis from syngas by Clostridium carboxidivorans P7 is enhanced by in‑line extraction with a biocompatible solvent to avoid product toxicity

Experimental Design to Improve Cell Growth and Ethanol Production in Syngas Fermentation by Clostridium carboxidivorans

Progress and development of syngas fermentation processes toward commercial bioethanol production

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