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Updated: Jul 10, 2025
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Techniques for the Evolution of Robust Pentose-fermenting Yeast for Bioconversion of Lignocellulose to Ethanol
Published on: October 24, 2016
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Deciphering anaerobic ethanol metabolic pathways shaped by operational modes
Bang Du1, Xinmin Zhan1, Piet N L Lens2
1Civil Engineering, School of Engineering, College of Science and Engineering, University of Galway, Galway H91 TK33, Ireland.
Water Research
|November 25, 2023
Summary
Sequencing batch reactors (SBRs) enhance ethanol metabolism and methanogenesis. Long-term powdered activated carbon (PAC) addition boosts ethanol degradation and propionate production, while favoring Geobacter enrichment in continuous-flow reactors (CFRs).
Area of Science:
- Microbiology
- Environmental Science
- Biotechnology
Background:
- Efficient anaerobic digestion relies on microbial syntrophy and diverse metabolic pathways.
- Understanding ethanol metabolic pathways is crucial for optimizing biogas production.
Purpose of the Study:
- To investigate the effects of sequencing batch reactor (SBR) and continuous-flow reactor (CFR) operational modes, with and without powdered activated carbon (PAC), on ethanol metabolic pathways.
- To identify strategies for modulating anaerobic ethanol metabolism and enriching specific microbial communities like Geobacter.
Main Methods:
- Comparison of SBR and CFR systems fed with ethanol.
- Assessment of powdered activated carbon (PAC) addition effects (short-term and long-term).
- Analysis of microbial community composition, enzyme activities (EC: 1.2.7.1, EC: 1.2.7.11), sludge conductivity, and metabolic rates (ethanol degradation, methanogenesis, propionate production/degradation).
Main Results:
- SBR operation, especially with CO2, favored ethanol metabolism towards propionate, evidenced by Desulfobulbus dominance and increased CO2-metabolizing enzymes.
- SBRs showed significantly higher biomass-based rates for ethanol degradation (53.1%) and methanogenesis (22.3%) compared to CFRs.
- Extended solids retention time in CFRs enriched Geobacter (71.7% and 70.4% with/without PAC).
- Long-term PAC addition enhanced ethanol degradation and propionate metabolism, while both short-term and long-term additions reduced the methanogenic lag phase and increased sludge conductivity.
Conclusions:
- Operational mode (SBR vs. CFR) and PAC addition are effective strategies for controlling anaerobic ethanol metabolic pathways.
- SBRs promote propionate production and enhance overall degradation and methanogenesis rates.
- Long-term PAC addition is beneficial for improving ethanol degradation and propionate metabolism, and CFRs with extended solids retention time can enrich for Geobacter.
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