Improving medium chain fatty acid productivity using chain elongation by reducing the hydraulic retention time in an upflow anaerobic filter

Grootscholten, T.I.M.; Steinbusch, K.J.J.; Hamelers, H.V.M.; Buisman, C.J.N.

doi:10.1016/j.biortech.2013.02.114

Cited by 139 publications

(142 citation statements)

References 16 publications

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“…For example, ethanol production has been observed at pH 5.3 in a single-stage bioreactor with optimum growth (Mock et al, 2015). On the contrary, chain elongation to n -caproate or n -caprylate without product extraction is optimal at a neutral pH level of 6.5–7.5 (Grootscholten et al, 2013). Chain elongation was considerably inhibited at mildly acidic conditions due to the high toxicity of undissociated medium-chain carboxylic acids (pKa ~ 4.9) (Spirito et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

A Narrow pH Range Supports Butanol, Hexanol, and Octanol Production from Syngas in a Continuous Co-culture of Clostridium ljungdahlii and Clostridium kluyveri with In-Line Product Extraction

et al. 2016

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Carboxydotrophic bacteria (CTB) have received attention due to their ability to synthesize commodity chemicals from producer gas and synthesis gas (syngas). CTB have an important advantage of a high product selectivity compared to chemical catalysts. However, the product spectrum of wild-type CTB is narrow. Our objective was to investigate whether a strategy of combining two wild-type bacterial strains into a single, continuously fed bioprocessing step would be promising to broaden the product spectrum. Here, we have operated a syngas-fermentation process with Clostridium ljungdahlii and Clostridium kluyveri with in-line product extraction through gas stripping and product condensing within the syngas recirculation line. The main products from C. ljungdahlii fermentation at a pH of 6.0 were ethanol and acetate at net volumetric production rates of 65.5 and 431 mmol C·L−1·d−1, respectively. An estimated 2/3 of total ethanol produced was utilized by C. kluyveri to chain elongate with the reverse β-oxidation pathway, resulting in n-butyrate and n-caproate at net rates of 129 and 70 mmol C·L−1·d−1, respectively. C. ljungdahlii likely reduced the produced carboxylates to their corresponding alcohols with the reductive power from syngas. This resulted in the longer-chain alcohols n-butanol, n-hexanol, and n-octanol at net volumetric production rates of 39.2, 31.7, and 0.045 mmol C·L−1·d−1, respectively. The continuous production of the longer-chain alcohols occurred only within a narrow pH spectrum of 5.7–6.4 due to the pH discrepancy between the two strains. Regardless whether other wild-type strains could overcome this pH discrepancy, the specificity (mol carbon in product per mol carbon in all other liquid products) for each longer-chain alcohol may never be high in a single bioprocessing step. This, because two bioprocesses compete for intermediates (i.e., carboxylates): (1) chain elongation; and (2) biological reduction. This innate competition resulted in a mixture of n-butanol and n-hexanol with traces of n-octanol.

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Section: Introductionmentioning

confidence: 99%

A Narrow pH Range Supports Butanol, Hexanol, and Octanol Production from Syngas in a Continuous Co-culture of Clostridium ljungdahlii and Clostridium kluyveri with In-Line Product Extraction

et al. 2016

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“…The production of MCFAs is done by micro-organisms using the reverse -oxidation pathway for chain elongation [4]. In recent years, researchers have demonstrated MCFA production rates with chain elongation up to 57 g•L -1 •d -1 [5]. Retaining the active micro-organisms (i.e.…”

Section: Introductionmentioning

confidence: 99%

Granular sludge formation and characterization in a chain elongation process

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Steinbusch

et al. 2016

Process Biochemistry

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“…n -Caproate has been produced with reactor microbiomes from ethanol (Levy et al, 1981; Steinbusch et al, 2011; Agler et al, 2012), carbohydrates (Wang et al, 2007; Ding et al, 2010), and lactate (Zhu et al, 2015; Kucek et al, 2016a) as electron donors. Ethanol-fed bioreactors have demonstrated superior n -caproate productivities (Grootscholten et al, 2013c). In addition, n -caprylate has only been produced when ethanol was the electron donor (Angenent et al, 2016; Kucek et al, 2016b).…”

Section: Introductionmentioning

confidence: 99%

Waste Conversion into n-Caprylate and n-Caproate: Resource Recovery from Wine Lees Using Anaerobic Reactor Microbiomes and In-line Extraction

et al. 2016

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To convert wastes into sustainable liquid fuels and chemicals, new resource recovery technologies are required. Chain elongation is a carboxylate-platform bioprocess that converts short-chain carboxylates (SCCs) (e.g., acetate [C2] and n-butyrate [C4]) into medium-chain carboxylates (MCCs) (e.g., n-caprylate [C8] and n-caproate [C6]) with hydrogen gas as a side product. Ethanol or another electron donor (e.g., lactate, carbohydrate) is required. Competitive MCC productivities, yields (product vs. substrate fed), and specificities (product vs. all products) were only achieved previously from an organic waste material when exogenous ethanol had been added. Here, we converted a real organic waste, which inherently contains ethanol, into MCCs with n-caprylate as the target product. We used wine lees, which consisted primarily of settled yeast cells and ethanol from wine fermentation, and produced MCCs with a reactor microbiome. We operated the bioreactor at a pH of 5.2 and with continuous in-line extraction and achieved a MCC productivity of 3.9 g COD/L-d at an organic loading rate of 5.8 g COD/L-d, resulting in a promising MCC yield of 67% and specificities of 36% for each n-caprylate and n-caproate (72% for both). Compared to all other studies that used complex organic substrates, we achieved the highest n-caprylate-to-ncaproate product ratio of 1.0 (COD basis), because we used increased broth-recycle rates through the forward membrane contactor, which improved in-line extraction rates. Increased recycle rates also allowed us to achieve the highest reported MCC production flux per membrane surface area thus far (20.1 g COD/m2-d). Through microbial community analyses, we determined that an operational taxonomic unit (OTU) for Bacteroides spp. was dominant and was positively correlated with increased MCC productivities. Our data also suggested that the microbiome may have been shaped for improved MCC production by the high broth-recycle rates. Comparable abiotic studies suggest that further increases in the broth-recycle rates could improve the overall mass transfer coefficient and its corresponding MCC production flux by almost 30 times beyond the maximum that we achieved. With improved in-line extraction, the chain-elongation biotechnology production platform offers new opportunities for resource recovery and sustainable production of liquid fuels and chemicals.

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Improving medium chain fatty acid productivity using chain elongation by reducing the hydraulic retention time in an upflow anaerobic filter

Cited by 139 publications

References 16 publications

A Narrow pH Range Supports Butanol, Hexanol, and Octanol Production from Syngas in a Continuous Co-culture of Clostridium ljungdahlii and Clostridium kluyveri with In-Line Product Extraction

A Narrow pH Range Supports Butanol, Hexanol, and Octanol Production from Syngas in a Continuous Co-culture of Clostridium ljungdahlii and Clostridium kluyveri with In-Line Product Extraction

Granular sludge formation and characterization in a chain elongation process

Waste Conversion into n-Caprylate and n-Caproate: Resource Recovery from Wine Lees Using Anaerobic Reactor Microbiomes and In-line Extraction

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