Abstract
Anaerobic microbial communities can produce carboxylic acids of medium chain length (e.g., caproate, caprylate) by elongating short chain fatty acids through reversed β-oxidation. Ethanol is a common electron donor for this process. The influence of environmental conditions on the stoichiometry and kinetics of ethanol-based chain elongation remains elusive. Here, a sequencing batch bioreactor setup with high-resolution off-gas measurements was used to identify the physiological characteristics of chain elongating microbial communities enriched on acetate and ethanol at pH 7.0 ± 0.2 and 5.5 ± 0.2. Operation at both pH-values led to the development of communities that were highly enriched (>50%, based on 16S rRNA gene amplicon sequencing) in Clostridium kluyveri related species. At both pH-values, stably performing cultures were characterized by incomplete substrate conversion and decreasing biomass-specific hydrogen production rates during an operational cycle. The process stoichiometries obtained at both pH-values were different: at pH 7.0, 71 ± 6% of the consumed electrons were converted to caproate, compared to only 30 ± 5% at pH 5.5. Operating at pH 5.5 led to a decrease in the biomass yield, but a significant increase in the biomass-specific substrate uptake rate, suggesting that the organisms employ catabolic overcapacity to deal with energy losses associated to product inhibition. These results highlight that chain elongating conversions rely on a delicate balance between substrate uptake- and product inhibition kinetics.
Original language | English |
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Article number | 693030 |
Number of pages | 9 |
Journal | Frontiers in Bioengineering and Biotechnology |
Volume | 9 |
DOIs | |
Publication status | Published - 2021 |
Keywords
- anaerobic
- butyrate
- caproate
- Clostridium kluyveri
- enrichment
- fermentation
- product inhibition
- reversed beta-oxidation
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Dive into the research topics of 'Product Inhibition and pH Affect Stoichiometry and Kinetics of Chain Elongating Microbial Communities in Sequencing Batch Bioreactors'. Together they form a unique fingerprint.Datasets
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Data underlying the publication: Product inhibition and pH affect stoichiometry and kinetics of chain elongating microbial communities in sequencing batch bioreactors - 16S data
Kleerebezem, R. (Creator), Sousa, D. Z. (Creator), Stouten, G. R. (Creator) & Allaart, M. T. (Creator), TU Delft - 4TU.ResearchData, 4 Oct 2023
DOI: 10.4121/14394578, https://doi.org/https://doi.org/10.3389/fbioe.2021.693030
Dataset/Software: Dataset