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Title: Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate

Here, volatile fatty acids (VFAs) can be readily produced from many anaerobic microbes and subsequently utilized as precursors to renewable biofuels and biochemicals. Megasphaera elsdenii represents a promising host for production of VFAs, butyric acid (BA) and hexanoic acid (HA). However, due to the toxicity of these acids, product removal via an extractive fermentation system is required to achieve high titers and productivities. Here, we examine multiple aspects of extractive separations to produce BA and HA from glucose and lignocellulosic hydrolysate with M. elsdenii. A mixture of oleyl alcohol and 10% (v/v) trioctylamine was selected as an extraction solvent due to its insignificant inhibitory effect on the bacteria. Batch extractive fermentations were conducted in the pH range of 5.0 to 6.5 to select the best cell growth rate and extraction efficiency combination. Subsequently, fed-batch pertractive fermentations were run over 230 h, demonstrating high BA and HA concentrations in the extracted fraction (57.2 g/L from ~190 g/L glucose) and productivity (0.26 g/L/h). To our knowledge, these are the highest combined acid titers and productivity values reported for M. elsdenii and bacterial mono-cultures from sugars. Lastly, the production of BA and HA (up to 17 g/L) from lignocellulosic sugars was demonstrated.
Authors:
 [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5100-70383
Journal ID: ISSN 2311-5637
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Fermentation
Additional Journal Information:
Journal Volume: 3; Journal Issue: 1; Journal ID: ISSN 2311-5637
Publisher:
MDPI
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; butyric acid; hexanoic acid; caproic acid; volatile fatty acids; short-chain carboxylates; extractive fermentation; oleyl alcohol; corn stover; biochemical; biofuel
OSTI Identifier:
1405918

Nelson, Robert S., Peterson, Darren J., Karp, Eric M., Beckham, Gregg T., and Salvachua, Davinia Rodriguez. Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate. United States: N. p., Web. doi:10.3390/fermentation3010010.
Nelson, Robert S., Peterson, Darren J., Karp, Eric M., Beckham, Gregg T., & Salvachua, Davinia Rodriguez. Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate. United States. doi:10.3390/fermentation3010010.
Nelson, Robert S., Peterson, Darren J., Karp, Eric M., Beckham, Gregg T., and Salvachua, Davinia Rodriguez. 2017. "Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate". United States. doi:10.3390/fermentation3010010. https://www.osti.gov/servlets/purl/1405918.
@article{osti_1405918,
title = {Mixed Carboxylic Acid Production by Megasphaera elsdenii from Glucose and Lignocellulosic Hydrolysate},
author = {Nelson, Robert S. and Peterson, Darren J. and Karp, Eric M. and Beckham, Gregg T. and Salvachua, Davinia Rodriguez},
abstractNote = {Here, volatile fatty acids (VFAs) can be readily produced from many anaerobic microbes and subsequently utilized as precursors to renewable biofuels and biochemicals. Megasphaera elsdenii represents a promising host for production of VFAs, butyric acid (BA) and hexanoic acid (HA). However, due to the toxicity of these acids, product removal via an extractive fermentation system is required to achieve high titers and productivities. Here, we examine multiple aspects of extractive separations to produce BA and HA from glucose and lignocellulosic hydrolysate with M. elsdenii. A mixture of oleyl alcohol and 10% (v/v) trioctylamine was selected as an extraction solvent due to its insignificant inhibitory effect on the bacteria. Batch extractive fermentations were conducted in the pH range of 5.0 to 6.5 to select the best cell growth rate and extraction efficiency combination. Subsequently, fed-batch pertractive fermentations were run over 230 h, demonstrating high BA and HA concentrations in the extracted fraction (57.2 g/L from ~190 g/L glucose) and productivity (0.26 g/L/h). To our knowledge, these are the highest combined acid titers and productivity values reported for M. elsdenii and bacterial mono-cultures from sugars. Lastly, the production of BA and HA (up to 17 g/L) from lignocellulosic sugars was demonstrated.},
doi = {10.3390/fermentation3010010},
journal = {Fermentation},
number = 1,
volume = 3,
place = {United States},
year = {2017},
month = {3}
}

Works referenced in this record:

Another explanation for the toxicity of fermentation acids at low pH: anion accumulation versus uncoupling
journal, November 1992

Catalytic coupling of carboxylic acids by ketonization as a processing step in biomass conversion
journal, August 2009
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