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Characterization of volatile fatty-acid utilization in Escherichia coli aiming for robust valorisation of food residues

Authors
  • Sjöberg, Gustav1
  • Gustavsson, Martin1
  • van Maris, Antonius J. A.1
  • 1 KTH Royal Institute of Technology, Stockholm, Sweden , Stockholm (Sweden)
Type
Published Article
Journal
AMB Express
Publisher
Springer Berlin Heidelberg
Publication Date
Oct 17, 2020
Volume
10
Issue
1
Identifiers
DOI: 10.1186/s13568-020-01121-4
Source
Springer Nature
Keywords
License
Green

Abstract

Valorisation of food residues would greatly benefit from development of robust processes that create added value compared to current feed- and biogas applications. Recent advances in membrane-bioreactor-based open mixed microbial cultures, enable robust conversion of fluctuating streams of food residues to a mixture of volatile fatty acids (VFAs). In this study, such a mixed stream of VFAs was investigated as a substrate for Escherichia coli, a well-studied organism suitable for application in further conversion of the acids into compounds of higher value, and/or that are easier to separate from the aqueous medium. E. coli was cultured in batch on a VFA-rich anaerobic digest of food residues, tolerating up to 40 mM of total VFAs without any reduction in growth rate. In carbon-limited chemostats of E. coli W3110 ΔFadR on a simulated VFA mixture, the straight-chain VFAs (C2-C6) in the mixture were readily consumed simultaneously. At a dilution rate of 0.1 h−1, mainly acetic-, propionic- and caproic acid were consumed, while consumption of all the provided acids were observed at 0.05 h−1. Interestingly, also the branched isovaleric acid was consumed through a hitherto unknown mechanism. In total, up to 80% of the carbon from the supplied VFAs was consumed by the cells, and approximately 2.7% was excreted as nucleotide precursors in the medium. These results suggest that VFAs derived from food residues are a promising substrate for E. coli.

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