Branched Medium Chain Fatty Acids: Iso-Caproate Formation from Iso-Butyrate Broadens the Product Spectrum for Microbial Chain Elongation

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Chain elongation fermentation can be used to convert organic residues into biobased chemicals. This research aimed to develop a bioprocess for branched medium chain fatty acids (MCFAs) production. A long-term continuous reactor experiment showed that iso-caproate (4-methyl pentanoate, i-C6) can be produced via ethanol based chain elongation. The enriched microbiome formed iso-caproate from iso-butyrate at a rate of 44 ± 6 mmol C L-1 day-1 during the last phase. This amounted to 20% of all formed compounds based on carbon atoms. The main fermentation product was n-caproate (55% of all carbon), as a result of acetate and subsequent n-butyrate elongation. The microbiome preferred straight-chain elongation over branched-chain elongation. Lowering the acetate concentration in the influent led to an increase of excessive ethanol oxidation (EEO) into electron equivalents (e.g., H2) and acetate. The formed acetate in turn stimulated straight chain elongation, but the resulting lower net acetate supply rate towards straight chain elongation led to an increased selectivity towards and productivity of i-C6. The electrons produced via oxidation routes and chain elongation were apparently utilized by hydrogenotrophic methanogens, homoacetogens, and carboxylate-to-alcohol reducing bacteria. Further improvements could be achieved if the acetate-producing EEO was minimized and limitations of ethanol and CO2 were prevented.

LanguageEnglish
Pages7704-7713
JournalEnvironmental Science and Technology
Volume53
Issue number13
DOIs
Publication statusPublished - 4 Jun 2019

Fingerprint

Butyrates
Elongation
acetate
Fatty Acids
fatty acid
Acetates
ethanol
Ethanol
oxidation
fermentation
Oxidation
Fermentation
electron
Carbon
carbon
Methanogens
Valerates
hexanoic acid
product
Electrons

Cite this

@article{263e9a656c124a30b0daf9ef72ab3c8d,
title = "Branched Medium Chain Fatty Acids: Iso-Caproate Formation from Iso-Butyrate Broadens the Product Spectrum for Microbial Chain Elongation",
abstract = "Chain elongation fermentation can be used to convert organic residues into biobased chemicals. This research aimed to develop a bioprocess for branched medium chain fatty acids (MCFAs) production. A long-term continuous reactor experiment showed that iso-caproate (4-methyl pentanoate, i-C6) can be produced via ethanol based chain elongation. The enriched microbiome formed iso-caproate from iso-butyrate at a rate of 44 ± 6 mmol C L-1 day-1 during the last phase. This amounted to 20{\%} of all formed compounds based on carbon atoms. The main fermentation product was n-caproate (55{\%} of all carbon), as a result of acetate and subsequent n-butyrate elongation. The microbiome preferred straight-chain elongation over branched-chain elongation. Lowering the acetate concentration in the influent led to an increase of excessive ethanol oxidation (EEO) into electron equivalents (e.g., H2) and acetate. The formed acetate in turn stimulated straight chain elongation, but the resulting lower net acetate supply rate towards straight chain elongation led to an increased selectivity towards and productivity of i-C6. The electrons produced via oxidation routes and chain elongation were apparently utilized by hydrogenotrophic methanogens, homoacetogens, and carboxylate-to-alcohol reducing bacteria. Further improvements could be achieved if the acetate-producing EEO was minimized and limitations of ethanol and CO2 were prevented.",
author = "{De Leeuw}, {Kasper D.} and Buisman, {Cees J.N.} and Strik, {David P.B.T.B.}",
year = "2019",
month = "6",
day = "4",
doi = "10.1021/acs.est.8b07256",
language = "English",
volume = "53",
pages = "7704--7713",
journal = "Environmental Science and Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "13",

}

TY - JOUR

T1 - Branched Medium Chain Fatty Acids

T2 - Environmental Science and Technology

AU - De Leeuw, Kasper D.

AU - Buisman, Cees J.N.

AU - Strik, David P.B.T.B.

PY - 2019/6/4

Y1 - 2019/6/4

N2 - Chain elongation fermentation can be used to convert organic residues into biobased chemicals. This research aimed to develop a bioprocess for branched medium chain fatty acids (MCFAs) production. A long-term continuous reactor experiment showed that iso-caproate (4-methyl pentanoate, i-C6) can be produced via ethanol based chain elongation. The enriched microbiome formed iso-caproate from iso-butyrate at a rate of 44 ± 6 mmol C L-1 day-1 during the last phase. This amounted to 20% of all formed compounds based on carbon atoms. The main fermentation product was n-caproate (55% of all carbon), as a result of acetate and subsequent n-butyrate elongation. The microbiome preferred straight-chain elongation over branched-chain elongation. Lowering the acetate concentration in the influent led to an increase of excessive ethanol oxidation (EEO) into electron equivalents (e.g., H2) and acetate. The formed acetate in turn stimulated straight chain elongation, but the resulting lower net acetate supply rate towards straight chain elongation led to an increased selectivity towards and productivity of i-C6. The electrons produced via oxidation routes and chain elongation were apparently utilized by hydrogenotrophic methanogens, homoacetogens, and carboxylate-to-alcohol reducing bacteria. Further improvements could be achieved if the acetate-producing EEO was minimized and limitations of ethanol and CO2 were prevented.

AB - Chain elongation fermentation can be used to convert organic residues into biobased chemicals. This research aimed to develop a bioprocess for branched medium chain fatty acids (MCFAs) production. A long-term continuous reactor experiment showed that iso-caproate (4-methyl pentanoate, i-C6) can be produced via ethanol based chain elongation. The enriched microbiome formed iso-caproate from iso-butyrate at a rate of 44 ± 6 mmol C L-1 day-1 during the last phase. This amounted to 20% of all formed compounds based on carbon atoms. The main fermentation product was n-caproate (55% of all carbon), as a result of acetate and subsequent n-butyrate elongation. The microbiome preferred straight-chain elongation over branched-chain elongation. Lowering the acetate concentration in the influent led to an increase of excessive ethanol oxidation (EEO) into electron equivalents (e.g., H2) and acetate. The formed acetate in turn stimulated straight chain elongation, but the resulting lower net acetate supply rate towards straight chain elongation led to an increased selectivity towards and productivity of i-C6. The electrons produced via oxidation routes and chain elongation were apparently utilized by hydrogenotrophic methanogens, homoacetogens, and carboxylate-to-alcohol reducing bacteria. Further improvements could be achieved if the acetate-producing EEO was minimized and limitations of ethanol and CO2 were prevented.

U2 - 10.1021/acs.est.8b07256

DO - 10.1021/acs.est.8b07256

M3 - Article

VL - 53

SP - 7704

EP - 7713

JO - Environmental Science and Technology

JF - Environmental Science and Technology

SN - 0013-936X

IS - 13

ER -