Anaerobic fermentation for n-caproic acid production: A review

Cavalcante, Willame de Araújo; Leitão, Renato Carrhá; Gehring, Tito; Angenent, Largus T.; Santaella, Sandra Tédde

doi:10.1016/j.procbio.2016.12.024

Cited by 278 publications

(154 citation statements)

References 126 publications

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“…Fifteen enriched cultures able to perform chain elongation with ethanol as electron donor were obtained from 6 sources (3 full-scale AD plant, 2 types of animal faeces, and 1 lab-scale pilot installation fed on thin stillage). Under the applied conditions -ethanol and acetate as sole electron donors/acceptors, low sulfate concentrations (0.2 mM) and BES addition to inhibit methanogenesis -chain elongation is the only known thermodynamically feasible metabolism for microbial growth 30 . These selective conditions allowed for a clear investigation on the effect of pH and source of inoculum on the features of chain-elongating microorganisms.…”

Section: Discussion Inoculum Origin Determines the Operational Niche mentioning

confidence: 99%

Enrichment and characterisation of ethanol chain elongating communities from natural and engineered environments

Candry

Huang

Carvajal-Arroyo

et al. 2020

Sci Rep

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chain elongation is a microbial process in which an electron donor, such as ethanol, is used to elongate short chain carboxylic acids, such as acetic acid, to medium chain carboxylic acids. this metabolism has been extensively investigated, but the spread and differentiation of chain elongators in the environment remains unexplored. Here, chain elongating communities were enriched from several inocula (3 anaerobic digesters, 2 animal faeces and 1 caproic acid producing environment) using ethanol and acetic acid as substrates at pH 7 and 5.5. This approach showed that (i) the inoculum's origin determines the pH where native chain elongators can grow; (ii) pH affects caproic acid production, with average caproic acid concentrations of 6.4 ± 1.6 g·L −1 at pH 7, versus 2.3 ± 1.8 g·L −1 at pH 5.5; however (iii) pH does not affect growth rates significantly; (iv) all communities contained a close relative of the known chain elongator Clostridium kluyveri; and (v) low pH selects for communities more enriched in this Clostridium kluyveri-relative (57.6 ± 23.2% at pH 7, 96.9 ± 1.2% at pH 5.5). These observations show that ethanol-consuming chain elongators can be found in several natural and engineered environments, but are not the same everywhere, emphasising the need for careful inoculum selection during process development.Carboxylic acids with carbon chains of six to twelve carbon atoms, also named medium chain carboxylic acids (MCCA), are a group of chemicals with a wide range of potential applications; as antimicrobial agents in feed and fodder these chemicals could replace conventional antibiotics, while they can also be used as a corrosion inhibitor 1 . Furthermore, chemical derivatization of MCCA creates additional product opportunities, e.g. esterification of MCCA can lead to a range of fragrance and flavour products for use in cosmetics and food 2 . On top of that, conversion of the carboxylic acids to their relative alcohols and alkanes, can supply solvents and fuels 3 , while Kolbe electrolysis of MCCA allows the production of long chain alkanes from MCCA, for instance decane, usable as jet-fuel 4 .Caproic acid, the shortest of the MCCA (six-carbon chain), is currently sourced from plant oils and animal fats 5 with a production capacity of 25,000 tonnes per year and a market value of approx. €2000/tonne 6 . It has generated great research interest because of the aforementioned application potential, in combination with the possibility of sustainable sourcing of caproic acid through bioproduction from waste streams, such as organic wastes and syngas 7-9 . This bioproduction occurs through the so-called reversed-β oxidation pathway, by which an electron donor, such as ethanol, is converted to acetyl-coA. This acetyl-CoA is then used in a cyclical process that converts acetic acid to butyric acid, which is in turn converted to caproic acid. This stepwise two-carbon increase of the carboxylic acid acyl-chain is why this metabolism is often named chain elongation. Clostridium kluyveri was the first isolated bacter...

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Section: Discussion Inoculum Origin Determines the Operational Niche mentioning

confidence: 99%

Enrichment and characterisation of ethanol chain elongating communities from natural and engineered environments

Candry

Huang

Carvajal-Arroyo

et al. 2020

Sci Rep

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“…1) is another representative mediumchain VFA, which acts as a flavoring agent primarily used for cheese, cream, and fruit flavors. 66 Megasphaera hexanoica was considered as a promising strain for caproic acid production owing to its fast production rates when acetic and / or butyric acid was supplied. 67 Co-cultivation of M. hexanoica with acetic and / or butyric acid producers, such as C. tyrobutyricum, could achieve caproic acid production from renewable resources.…”

Section: Xylonic Acidmentioning

confidence: 99%

Current advances in organic acid production from organic wastes by using microbial co‐cultivation systems

Qian

et al. 2019

Biofuels Bioprod Bioref

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The microbial production of organic acids has become a rapidly developing field due to their increasing global market. Recently, research has transitioned towards employing synthetic microbial consortia for organic acid production. Compared with pure cultures, microbial co‐cultures can perform more complex functions and endure more changeable environments. Accordingly, microbial co‐cultivation technologies for organic acid production have been adopted to fulfill the requirements for the utilization of a wider range of substrates for a higher product yield. Here, we have summarized current advances towards organic acid production from different substrates by using microbial co‐cultivation technologies. Furthermore, the construction mechanism of the microbial co‐cultivation systems was also analyzed and compared. © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

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“…C. kluyveri is capable of producing caproic acid with ethanol and acetate or butyrate (Bing et al, 2016;Kenealy & Waselefsky, 1985;Seedorf et al, 2008). The biosynthesis pathway of caproic acid has been described via reverse beta oxidation of acetic and/or butyric acid in C. kluyveri (Cavalcante, Leitão, Gehring, Angenent, & Santaella, 2017;Spirito, Richter, Rabaey, Stams, & Angenent, 2014). The ratio of ethanol to acetate (REA) has a great effect on the yield of butyrate and caproic acid.…”

Section: Physiological and Metabolic Features Of Clostridium In Sfb Ementioning

confidence: 99%

Diversity, Function, and Application of Clostridium in Chinese Strong Flavor Baijiu Ecosystem: A Review

Zou

Zhang

2018

Journal of Food Science

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Strong flavor baijiu (SFB) accounts for more than 70% of total yield of Chinese baijiu, which exists for hundreds of years. Clostridium is common in SFB ecosystem and identified to be one of main contributors of flavor compounds in SFB. Study on the Clostridium from SFB ecosystem is not only helpful for the understanding of flavor compounds formation mechanism, but also the improvement of SFB quality. This study focuses on the current researches on the Clostridium species in SFB ecosystem, including the species diversity, physiological and metabolic features, and applications.

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Anaerobic fermentation for n-caproic acid production: A review

Cited by 278 publications

References 126 publications

Enrichment and characterisation of ethanol chain elongating communities from natural and engineered environments

Enrichment and characterisation of ethanol chain elongating communities from natural and engineered environments

Current advances in organic acid production from organic wastes by using microbial co‐cultivation systems

Diversity, Function, and Application of Clostridium in Chinese Strong Flavor Baijiu Ecosystem: A Review

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