Redox mediators modify end product distribution in biomass fermentations by mixed ruminal microbes in vitro

The fermentation system of mixed ruminal bacteria is capable of generating large amounts of short-chain volatile fatty acids (VFA) via the carboxylate platform in vitro. These VFAs are subject to elongation to larger, more energy-dense products through reverse β-oxidation, and the resulting products...

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Bibliographic Details
Published inAMB Express Vol. 5; no. 1; pp. 130 - 8
Main Authors Nerdahl, Michael A, Weimer, Paul J
Format Journal Article
LanguageEnglish
Published Berlin/Heidelberg Springer Berlin Heidelberg 04.08.2015
Springer Nature B.V
Subjects
beta oxidation
biomass
Biomedical and Life Sciences
Biotechnology
carbon
dyes
energy
fermentation
gas production (biological)
in vitro studies
Life Sciences
methane
methane production
Microbial Genetics and Genomics
Microbiology
Original
Original Article
Panicum virgatum
paraquat
redox reactions
rumen bacteria
rumen fermentation
tannins
volatile fatty acids
Methane
Electron mediator
Rumen
Redox dye
Volatile fatty acids
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Summary:The fermentation system of mixed ruminal bacteria is capable of generating large amounts of short-chain volatile fatty acids (VFA) via the carboxylate platform in vitro. These VFAs are subject to elongation to larger, more energy-dense products through reverse β-oxidation, and the resulting products are useful as precursors for liquid fuels production. This study examined the effect of several redox mediators (neutral red, methyl viologen, safranin O, tannic acid) as alternative electron carriers for mixed ruminal bacteria during the fermentation of biomass (ground switchgrass not subjected to other pretreatments) and their potential to enhance elongation of end-products to medium-chain VFAs with no additional run-time. Neutral red (1 mM) in particular facilitated chain elongation, increasing average VFA chain length from 2.42 to 2.97 carbon atoms per molecule, while simultaneously inhibiting methane accumulation by over half yet maintaining total C in end products. The ability of redox dyes to act as alternative electron carriers suggests that ruminal fermentation is inherently manipulable toward retaining a higher fraction of substrate energy in the form of VFA.
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ISSN:2191-0855
2191-0855
DOI:10.1186/s13568-015-0130-7