Medium chain carboxylic acids production from waste biomass: Current advances and perspectives

Wu, Qinglian; Bao, Xian; Guo, Wei; Wang, Bing; Li, Yunxi; Luo, Haichao; Wang, Huazhe; Ren, Nanqi

doi:10.1016/j.biotechadv.2019.03.003

Cited by 229 publications

(112 citation statements)

References 109 publications

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“…For example, n-caproate can be used as promoter of plant growth and feed additive, or as precursor for the production of biofuels, lubricants and fragrances [1,[4][5][6][7]. Currently, n-caproate is mainly produced from vegetable oils such as palm kernel oil [8], though it can be produced from more sustainable feedstocks such as agro-industrial waste by anaerobic fermentation and microbial chain elongation [9,10]. Compared to linear carboxylates, branched-chain carboxylates such as iso-butyrate are of special interest for alternative applications due to their different physical properties, including higher viscosity, higher oxidative stability, and a lower boiling point [11].…”

Section: Introductionmentioning

confidence: 99%

“…To date, only few chain-elongating bacteria have been isolated that utilize lactate to produce n-caproate, including strains of Megasphaera elsdenii, Megasphaera hexanoica, Pseudoramibacter alactolyticus and Ruminococcaceae bacterium CPB6. It has been assumed that the mechanism of chain elongation with lactate is similar to that described for chain elongation with ethanol [10,15]. However, insu cient knowledge has been generated yet on the physiology of lactate-based chain elongation from pure culture studies, and there is a lack of genome-level information to explore the genetic characteristics shared by chain-elongating bacteria.…”

Section: Introductionmentioning

confidence: 99%

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Lactate-based microbial chain elongation for n-caproate and iso-butyrate production: genomic and metabolic features of three novel Clostridia isolates

Liu

Popp

Sträuber

et al. 2020

Preprint

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Background The platform chemicals n-caproate and iso-butyrate can be produced by anaerobic fermentation from agro-industrial residues in a process known as microbial chain elongation. A few chain-elongating species have been discovered to utilize lactate and used to study the physiology of lactate-based chain elongation in pure cultures. Recently we isolated three novel clostridial species (strains BL-3, BL-4 and BL-6) that convert lactate to n-caproate and iso-butyrate. Here, we analyzed the genetic background of lactate-based chain elongation in these strains and other chain-elongating species by comparative genomics. Results All three strains produced n-caproate and iso-butyrate from lactate, with the highest proportions of n-caproate (18%) for BL-6 and iso-butyrate (23%) for BL-4 in batch cultivation at pH 5.5. The strains are suggested to represent three novel species based on low similarities with their closest described relatives. The three genomes show low conservation of organization and a relatively small core-genome size (504 out of 6,654 gene families). Including data of another eleven experimentally validated chain-elongating strains, we found that the chain elongation-specific core-genome harbors genes involved in reverse β-oxidation, hydrogen formation and energy conservation, displaying substantial genome heterogeneity. The three new isolates contain the genes for lactate oxidation and a gene cluster encoding enzymes of reverse β-oxidation, including the CoA transferase for the formation of n-caproate. Our analysis gave no hints on the isomerization pathway for iso-butyrate formation. An operon encoding the Rnf complex was found in BL-3 and BL-4 but not in BL-6, which may instead use the Ech hydrogenase complex for energy conservation. BL-3 and BL-6 were predicted to have genes encoding both the BCD/EtfAB complex and the LDH/EtfAB complex for energy coupling. Conclusions The genetic background of lactate-based chain elongation was confirmed in three novel Clostridia species that convert lactate to n-caproate and iso-butyrate. They contain highly conserved genes involved in reverse β-oxidation, hydrogen formation and either of two types of energy conservation systems (Rnf and Ech). Further research is needed to elucidate the mechanism of iso-butyrate formation in these strains. Features of the three isolates may be interesting for further applications in n-caproate and iso-butyrate production.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lactate-based microbial chain elongation for n-caproate and iso-butyrate production: genomic and metabolic features of three novel Clostridia isolates

Liu

Popp

Sträuber

et al. 2020

Preprint

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“…They comprise a subset of building blocks identified by the U.S. Department of Energy (DOE) as top value-added chemical production candidates from terrestrial biomass (Werpy and Petersen, 2004). Indeed, recent work has underscored the utility of carboxylic acids as valuable precursors for fuel and polymer production, and demonstrated novel catalytic routes to upgrade carboxylates to jet and diesel blendstocks as well as high-value polymers (Henard et al, 2016;Guarnieri et al, 2017;Karp et al, 2017;Huo et al, 2019;Medoff et al, 2019;Wu et al, 2019). These technologies serve as proof-of-principle for the development of green bioproduction routes that have the potential to substantially displace petroleum-derived fuels and chemicals.…”

Section: Introductionmentioning

confidence: 99%

Development of Clostridium tyrobutyricum as a Microbial Cell Factory for the Production of Fuel and Chemical Intermediates From Lignocellulosic Feedstocks

et al. 2020

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Microbial conversion of lignocellulosic substrates to fuel and platform chemical intermediates offers a sustainable route to establish a viable bioeconomy. However, such approaches face a series of key technical, economic, and sustainability hurdles, including: incomplete substrate utilization, lignocellulosic hydrolysate, and/or endproduct toxicity, inefficient product recovery, incompatible cultivation requirements, and insufficient productivity metrics. Development of a production host with native traits suitable for high productivity conversion of lignocellulosic substrates under process-relevant conditions offers a means to bypass the above-described hurdles and accelerate the development of microbial biocatalyst deployment. Clostridium tyrobutyricum, a native producer of short chain fatty acids, displays a series of characteristics that make it an ideal candidate for conversion of lignocellulosic substrates and thus represents a promising host for microbial production of diverse carboxylate-derived product suites. Herein, recent progress and future directions in the development of this bacterium as an industrial microbial cell factory, with emphases on the utilization of lignocellulosic substrates and metabolic engineering approaches, is reviewed.

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“…此外, Firmicutes是链延长过程的重要参与者, 目前已发现的主要链延长菌株均属于Firmicutes [16] . Firmicutes菌群中, Clostridia是主要菌群, 其相对丰度达到40.3%, 远高于其他反应器(接种泥中为18.3%, pH 5.6中为26.3%, pH 9.0中为28.1%).…”

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“…据报道, Clostridia菌群能够利用各种碳水化合物, 将其转化为小分子有机酸, 包括复杂纤维素、己糖和戊糖等 [17,18] . [16,20,23] . 由此可见, 混菌发酵中的链延长微生物菌群具有不同于纯菌发酵的特点, 不同菌群间可能存在更为密切的协同作用关系.…”

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Anaerobic chain elongation of cornstalk for MCFAs production via mixed culture: pH regulation

Zhu¹,

Dang²,

Zhang³

et al. 2020

Chin. Sci. Bull.

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Medium chain carboxylic acids production from waste biomass: Current advances and perspectives

Cited by 229 publications

References 109 publications

Lactate-based microbial chain elongation for n-caproate and iso-butyrate production: genomic and metabolic features of three novel Clostridia isolates

Lactate-based microbial chain elongation for n-caproate and iso-butyrate production: genomic and metabolic features of three novel Clostridia isolates

Development of Clostridium tyrobutyricum as a Microbial Cell Factory for the Production of Fuel and Chemical Intermediates From Lignocellulosic Feedstocks

Anaerobic chain elongation of cornstalk for MCFAs production via mixed culture: pH regulation

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