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Dynamics and Complexity of Dark Fermentation Microbial Communities Producing Hydrogen From Sugar Beet Molasses in
Anna Detman1, Daniel Laubitz2, Aleksandra Chojnacka1,3
1Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland.
Frontiers in Microbiology
|January 25, 2021
Summary
Optimizing hydrogen production from sugar beet molasses relies on balancing hydrogen-producing bacteria (HPB) and lactic acid bacteria (LAB). Specific ratios of HPB to LAB are crucial for stable and efficient fermentation, preventing shifts to less productive pathways.
Area of Science:
- Microbiology
- Biotechnology
- Bioreactor Engineering
Background:
- Sugar beet molasses is a viable substrate for biohydrogen production.
- Continuous operation of bioreactors in industrial settings presents unique challenges for microbial community stability.
- Understanding microbial dynamics is key to optimizing fermentation efficiency.
Purpose of the Study:
- To analyze the microbial community structure and dynamics in packed-bed reactors (PBRs) for hydrogen production from sugar beet molasses.
- To identify the key microbial ratios influencing hydrogen production efficiency and stability.
- To elucidate the factors contributing to metabolic shifts in dark fermentation (DF) bioreactors.
Main Methods:
- 16S rRNA profiling and shotgun metagenomics sequencing to analyze microbial communities.
- Testing of PBRs with varying volumes, packing materials, construction, and inocula.
- Correlation analysis between microbial community composition and hydrogen production rates.
Main Results:
- The ratio of hydrogen-producing bacteria (HPB) to lactic acid bacteria (LAB) significantly impacts hydrogen production efficiency.
- Optimal hydrogen yields (130-160 cm³/g COD) were achieved at HPB:LAB ratios of approximately 4:2.5 (16S rRNA) or 2.5:1 (metagenomics).
- Imbalances, such as LAB predominance or excessive clostridia, led to decreased hydrogen production and overproduction of short-chain fatty acids and ethanol.
Conclusions:
- A stable community balance between HPB and LAB is essential for efficient and consistent biohydrogen production.
- Bioreactor operating conditions (construction, packing, retention time, substrate concentration) influence this microbial balance.
- Ethanol concentration may serve as a marker for metabolic shifts away from hydrogen production in DF systems.
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