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Published on: August 15, 2019
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Carboxylic acids production via anaerobic fermentation: Microbial communities' responses to stepwise and direct
Mercedes Llamas1, Silvia Greses1, Elia Tomás-Pejó1
1Biotechnological Processes Unit, IMDEA Energy, Madrid, Spain.
Bioresource Technology
|November 9, 2021
Summary
This study shows that a stepwise reduction in hydraulic retention time (HRT) is crucial for stable anaerobic fermentation of waste into volatile fatty acids (VFAs). Gradual HRT decrease promotes microbial adaptation for optimal VFA production.
Area of Science:
- Biotechnology
- Environmental Science
- Microbiology
Background:
- Carboxylic acids are traditionally derived from fossil fuels.
- Renewable biomass offers a sustainable alternative for carboxylic acid production via anaerobic fermentation.
- Hydraulic retention time (HRT) critically influences microbial activity and process stability in bioprocesses.
Purpose of the Study:
- To investigate the relationship between process stability and microbial community dynamics during anaerobic fermentation.
- To compare stepwise versus direct hydraulic retention time (HRT) reduction strategies for waste bioconversion into volatile fatty acids (VFAs).
Main Methods:
- Assessed waste bioconversion into VFAs under different HRT reduction strategies (stepwise and direct).
- Monitored microbial community dynamics throughout the HRT decrease.
- Analyzed microbial similarity to identify key microbial groups involved in VFA production.
Main Results:
- Direct HRT reduction led to microbial fluctuations and process failure below 6 days HRT.
- Stepwise HRT reduction strategy facilitated microbial adaptation and achieved maximum bioconversion efficiency (32% VFACOD/tCODin) at 4 days HRT.
- Clostridiales, Lactobacillales, and Bacteroidales orders were identified as key microorganisms for VFA production, protein degradation, and propionic acid accumulation.
Conclusions:
- A stepwise HRT reduction strategy is essential for maintaining process stability and optimizing VFA production from waste.
- Microbial specialization occurs with decreasing HRT, highlighting the importance of adaptation.
- Specific microbial orders play critical roles in the anaerobic fermentation of waste into valuable VFAs.
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