Chain elongation with reactor microbiomes: upgrading dilute ethanol to medium-chain carboxylates

Agler, Matthew T.; Spirito, Catherine M.; Usack, Joseph G.; Werner, Jeffrey J.; Angenent, Largus T.

doi:10.1039/c2ee22101b

Cited by 306 publications

(336 citation statements)

References 15 publications

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“…Clostridium species are often associated with chain elongation of fatty acids (31). The association between Clostridium populations and valerate production in this study is consistent with previous studies and may relate to the reverse beta oxidation pathway used by organisms such as Clostridium kluyveri (32), although typically this is investigated for even-numbered carboxylates.…”

Section: Figsupporting

confidence: 89%

Dynamics of Cathode-Associated Microbial Communities and Metabolite Profiles in a Glycerol-Fed Bioelectrochemical System

Dennis

Yeoh

Tyson

et al. 2013

Appl Environ Microbiol

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e Electrical current can be used to supply reducing power to microbial metabolism. This phenomenon is typically studied in pure cultures with added redox mediators to transfer charge. Here, we investigate the development of a current-fed mixed microbial community fermenting glycerol at the cathode of a bioelectrochemical system in the absence of added mediators and identify correlations between microbial diversity and the respective product outcomes. Within 1 week of inoculation, a Citrobacter population represented 95 to 99% of the community and the metabolite profiles were dominated by 1,3-propanediol and ethanol. Over time, the Citrobacter population decreased in abundance while that of a Pectinatus population and the formation of propionate increased. After 6 weeks, several Clostridium populations and the production of valerate increased, which suggests that chain elongation was being performed. Current supply was stopped after 9 weeks and was associated with a decrease in glycerol degradation and alcohol formation. This decrease was reversed by resuming current supply; however, when hydrogen gas was bubbled through the reactor during open-circuit operation (open-circuit potential) as an alternative source of reducing power, glycerol degradation and metabolite production were unaffected. Cyclic voltammetry revealed that the community appeared to catalyze the hydrogen evolution reaction, leading to a ؉400-mV shift in its onset potential. Our results clearly demonstrate that current supply can alter fermentation profiles; however, further work is needed to determine the mechanisms behind this effect. In addition, operational conditions must be refined to gain greater control over community composition and metabolic outcomes.

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Section: Figsupporting

confidence: 89%

Dynamics of Cathode-Associated Microbial Communities and Metabolite Profiles in a Glycerol-Fed Bioelectrochemical System

Dennis

Yeoh

Tyson

et al. 2013

Appl Environ Microbiol

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“…Pertractive fermentation (a means of recovering the product in base as a result of product stripping from the organic solvent) has been used to improve productivity and to mitigate solvent toxicity for the production of BA and propionic acids [11,30] as well as HA from mixed culture fermentations [25,38]. The current work is a demonstration of this technique for the production and extraction of both BA and HA from M. elsdenii fermentation.…”

Section: Fed-batch Pertractive Fermentationmentioning

confidence: 99%

Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

et al. 2017

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Volatile fatty acids (VFAs) can be readily produced from many anaerobic microbes and subsequently utilized as precursors to renewable biofuels and biochemicals. Megasphaera elsdenii represents a promising host for production of VFAs, butyric acid (BA) and hexanoic acid (HA). However, due to the toxicity of these acids, product removal via an extractive fermentation system is required to achieve high titers and productivities. Here, we examine multiple aspects of extractive separations to produce BA and HA from glucose and lignocellulosic hydrolysate with M. elsdenii. A mixture of oleyl alcohol and 10% (v/v) trioctylamine was selected as an extraction solvent due to its insignificant inhibitory effect on the bacteria. Batch extractive fermentations were conducted in the pH range of 5.0 to 6.5 to select the best cell growth rate and extraction efficiency combination. Subsequently, fed-batch pertractive fermentations were run over 230 h, demonstrating high BA and HA concentrations in the extracted fraction (57.2 g/L from~190 g/L glucose) and productivity (0.26 g/L/h). To our knowledge, these are the highest combined acid titers and productivity values reported for M. elsdenii and bacterial mono-cultures from sugars. Lastly, the production of BA and HA (up to 17 g/L) from lignocellulosic sugars was demonstrated.

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“…In brief, ethanol as electron donor is firstly oxidized into acetyl-CoA, which then enters the reverse β-oxidation cycle, and elongates acetate (electron acceptor) to form butyrate. Likewise, in the following step another two carbons (from acetyl-CoA) are further added to butyrate (electron acceptor) to form CA (Agler et al, 2012;Spirito et al, 2014). That is the so-called chain elongation mechanism.…”

mentioning

confidence: 99%

Complete genome sequence of Ruminococcaceae bacterium CPB6: A newly isolated culture for efficient n -caproic acid production from lactate

Tao

Zhu

Wang

et al. 2017

Journal of Biotechnology

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Chain elongation with reactor microbiomes: upgrading dilute ethanol to medium-chain carboxylates

Cited by 306 publications

References 15 publications

Dynamics of Cathode-Associated Microbial Communities and Metabolite Profiles in a Glycerol-Fed Bioelectrochemical System

Dynamics of Cathode-Associated Microbial Communities and Metabolite Profiles in a Glycerol-Fed Bioelectrochemical System

Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

Complete genome sequence of Ruminococcaceae bacterium CPB6: A newly isolated culture for efficient n -caproic acid production from lactate

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