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

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Abstract

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% (ν/ν) 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.

Original languageAmerican English
Article number3010010
Number of pages16
JournalFermentation
Volume3
Issue number1
DOIs
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017 by the authors.

NREL Publication Number

  • NREL/JA-5100-70383

Keywords

  • Biochemical
  • Biofuel
  • Butyric acid
  • Caproic acid
  • Corn stover
  • Extractive fermentation
  • Hexanoic acid
  • Oleyl alcohol
  • Short-chain carboxylates
  • Volatile fatty acids

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