| Přispěvatelé: |
UCL - SST/ELI/ELIM - Applied Microbiology, UCL - Ingénierie biologique, agronomique et environnementale, Gerin, Patrick, Agathos, Spiros, Mahillon, Jacques, Bragard, Claude, Delfosse, Philippe, Scholwin, Frank |
| Popis: |
This thesis focused on the production of short chain carboxylates by mixed acidogenic fermentation, as a possible option for the sustainable valorisation of agroindustrial waste. Acidogenic fermentation is an intermediate step of standard anaerobic digestion, a process that sequentially converts organic matter mainly into methane. The product of acidogenic fermentation are short chain carboxylic acids, like acetic, propionic, butyric, caproic and lactic acids, with a variety of uses in green chemistry, renewable energy and other environmental applications. “Mixed fermentation” indicates the existence of natural consortia of microbial species treating composite substrates like lignocellulose, contrary to single, pure cultures treating simple substrates like glucose. The advantages of this approach include, among others, higher conversion capacities and increased flexibility in terms of substrate type, but the challenge of mastering the complexity of the fermentation system and the downstream processing of the products increases. We examined a variety of agroindustrial waste, such as fruit pulps and brewery residues among others, to highlight the relevance of mixed acidogenic fermentation as a stand-alone bioconversion process. We employed a variety of techniques (including among others wet chemistry, chromatography, DNA extraction, amplification and sequencing) to analyse the metabolic and microbial profile of fermentations and decipher their complexity. We were able to achieve carboxylate (mainly acetic, butyric and caproic acids) concentrations of approximately 41 gCOD/kg_mixed_liquor and substrate-to-carboxylate conversion yields of 0.64 gCOD_carboxylates/gCOD_substrate. We have shown that every substrate/inoculum combination leads to a unique and reproducible fermentation profile; a major factor for this uniqueness is the evolution and dynamics of the microbiome within each fermentation. We have highlighted, through the production of lactic acid from beer trub, the interest of mixed consortia not only as producers of target molecules but also as degraders of unwanted substances (inhibitory hop acids). We identified potential links between microbial species and metabolic products, but further research is needed to establish robust and direct correlations in a more systematic way. This would bring us a step closer to selective conversion of complex substrates into specific carboxylates and enable industrial use of mixed acidogenic fermentation. (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2018 |
