Production of C5 carboxylic acids in engineered Escherichia coli

Dhande, Yogesh K.; Xiong, Mei; Zhang, Kechun

doi:10.1016/j.procbio.2012.07.005

Cited by 12 publications

(6 citation statements)

References 26 publications

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“…When propanol was provided as electron donor, degradation of this alcohol to propionate (eq 3) was the main process in LB, but chain elongation to valerate (eq 18) increased from 11 to 27% of the total molar VFA production (Table S2) when the biomass concentration was increased. Valerate titers achieved in the HB test (16 mM; 1.63 g L –1 ) were comparable to those obtained from targeted engineered organisms (2.58 g L –1 ) . No methane production was detected in any of the tests performed.…”

Section: Resultssupporting

confidence: 51%

“…18) increased from 11 to 27% of the total molar VFA production (Table S2, supporting information) when the biomass concentration was increased. Valerate titers achieved in the HB test (16 mM; 1.63 g L -1 ) were comparable to those obtained from targeted engineered organisms (2.58 g L -1 ) 21 . No methane production was detected in any of the tests performed.…”

Section: Chain Elongation With Different Alcoholssupporting

confidence: 57%

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Product Diversity Linked to Substrate Usage in Chain Elongation by Mixed-Culture Fermentation

Coma

Vílchez-Vargas

Roume

et al. 2016

Environ. Sci. Technol.

121

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Acetate and ethanol can be converted to caproic acid by microorganisms through reverse β-oxidation. There is limited insight into the versatility of chain elongation in view of different starting substrates, including even- and odd-carbon carboxylates and alcohols other than ethanol. Thermodynamic analyses show that most elongation pathways are energetically feasible. Through incubations of microbial communities with different substrate-pair combinations, we established that ethanol and propanol were both highly suitable for chain elongation. As an electron acceptor, acetate, propionate, and butyrate readily elongated with ethanol, whereas an adaptation period was necessary for formate. Isobutyrate and longer-chained fatty acids above butyrate were not elongated. The microbial communities converged, and consistent enrichment of Clostridium spp. was observed, independent of the supplied alcohol or carboxylate, with a strain related to Clostridium kluyveri dominating the enrichments. Community analysis also showed phylotypes related to Bacteroidaceae and Microbacteriaceae families in all tests that are capable of converting the base substrates to useful intermediates. These organisms were mainly enriched with methanol or formate. Our overall conclusion is thus that multiple substrates can be used for chain elongation and that this process is carried out by highly similar organisms for direct chain elongation irrespective of the substrate.

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Section: Resultssupporting

confidence: 51%

Section: Chain Elongation With Different Alcoholssupporting

confidence: 57%

Product Diversity Linked to Substrate Usage in Chain Elongation by Mixed-Culture Fermentation

Coma

Vílchez-Vargas

Roume

et al. 2016

Environ. Sci. Technol.

121

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“…Figure S1 shows the pathway of producing BCFAs through catabolism of branched chain amino acid (Supporting Information). − In this process, multiple genes and their encoded enzymes have been identified in different strains including leucine dehydrogenase, α-keto acid dehydrogenase complex, α-keto acid decarboxylase, phosphotransbutyrylase, , and aldehyde dehydrogenase. , In B. subtilis , genes of leucine dehydrogenase ( bcd ), α-keto acid dehydrogenase complex ( bkdAA ), and α-keto acid decarboxylase ( bkdAB ) have been confirmed to be involved in BCFAs formation. , In Clostridium acetobutylicum , the phosphotransbutyrylase gene ( ptb ) was identified as the key gene in the BCFAs synthesis. , In Escherichia coli , aldehyde dehydrogenase gene has been reported to significantly affect BCFAs synthesis. , The genes of phosphotransbutyrylase ( ptb ) and aldehyde dehydrogenase ( dhaS ) have been predicted in B. subtilis genome, while their roles on BCFAs formation have not been investigated. More importantly, which gene is the most important one among these genes ( bcd , bkdAA , bkdAB , ptb , and dhaS ) is unknown in Bacillus subtilis , and identifying the key gene is necessary to solve the problem of natto odor.…”

Section: Introductionmentioning

confidence: 99%

Identification of a Key Gene Involved in Branched-Chain Short Fatty Acids Formation in Natto by Transcriptional Analysis and Enzymatic Characterization in Bacillus subtilis

Hong

Chen

et al. 2017

J. Agric. Food Chem.

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Natto as a fermented soybean product has many health benefits for human due to its rich nutritional and functional components. However, the unpleasant odor of natto, caused by the formation of branched-chain short fatty acids (BCFAs), prohibits the wide acceptance of natto products. This work is to identify the key gene of BCFAs formation and develop the guidance to reduce natto odor. Transcriptional analysis of BCFAs synthesis pathway genes was conducted in two Bacillus subtilis strains with obvious different BCFAs synthesis abilities. The transcriptional levels of bcd, bkdAA, and ptb in B. subtilis H-9 were 2.7-fold, 0.7-fold, and 8.9-fold higher than that of B. subtilis H-4, respectively. Therefore, the ptb gene with the highest transcriptional change was considered as the key gene in BCFAs synthesis. The ptb encoded enzyme Ptb was further characterized by inducible expression in Escherichia coli. The recombinant Ptb protein (about 32 kDa) was verified by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis analysis. The catalysis functions of Ptb were confirmed on substrates of isovaleryl-CoA and isobutyryl-CoA, and the higher catalysis efficiency of Ptb on isovaleryl-CoA explained the higher level of isovaleric acid in natto. The optimal activities of Ptb were observed at 50 °C and pH 8.0, and the enzymatic activity was inhibited by Ca, Zn, Ba, Mn, Cu, SDS, and EDTA. Collectively, this study reports a key gene responsible for BCFAs formation in natto fermentation and provides potential strategies to solve the odor problem.

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“…The production of higher alcohols (Atsumi et al, 2008;Zhang et al, 2008) and carboxylic acids (Dhande et al, 2012;Zhang et al, 2011) exploiting amino acid precursors has proven to be successful. These amino acid pathways generate 2-keto acids that can be converted into desired products.…”

Section: Introductionmentioning

confidence: 99%