1. Dynamics of dark fermentation microbial communities in the light of lactate and butyrate production
- Author
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Agnieszka Salamon, Anna Sikora, Anna Detman, Mieczysław Błaszczyk, Pawel R. Kiela, Albert Barberán, Yongjian Chen, Aleksandra Chojnacka, Daniel Laubitz, and Fei Yang
- Subjects
Microbiology (medical) ,Acidogenesis ,Microbial communities ,Butyrate ,Microbiology ,Microbial ecology ,03 medical and health sciences ,chemistry.chemical_compound ,Clostridium ,Bioreactors ,Lactic acid bacteria ,Leuconostoc ,Food science ,Lactic Acid ,030304 developmental biology ,0303 health sciences ,biology ,030306 microbiology ,Acetate ,Research ,Microbiota ,Nutritional interactions ,QR100-130 ,Dark fermentation ,biology.organism_classification ,Lactic acid ,Butyrates ,chemistry ,Fermentation ,Lactate ,Lactic acid fermentation - Abstract
Background This study focuses on the processes occurring during the acidogenic step of anaerobic digestion, especially resulting from nutritional interactions between dark fermentation (DF) bacteria and lactic acid bacteria (LAB). Previously, we have confirmed that DF microbial communities (MCs) that fed on molasses are able to convert lactate and acetate to butyrate. The aims of the study were to recognize the biodiversity of DF-MCs able and unable to convert lactate and acetate to butyrate and to define the conditions for the transformation. Results MCs sampled from a DF bioreactor were grown anaerobically in mesophilic conditions on different media containing molasses or sucrose and/or lactate and acetate in five independent static batch experiments. The taxonomic composition (based on 16S_rRNA profiling) of each experimental MC was analysed in reference to its metabolites and pH of the digestive liquids. In the samples where the fermented media contained carbohydrates, the two main tendencies were observed: (i) a low pH (pH ≤ 4), lactate and ethanol as the main fermentation products, MCs dominated with Lactobacillus, Bifidobacterium, Leuconostoc and Fructobacillus was characterized by low biodiversity; (ii) pH in the range 5.0–6.0, butyrate dominated among the fermentation products, the MCs composed mainly of Clostridium (especially Clostridium_sensu_stricto_12), Lactobacillus, Bifidobacterium and Prevotella. The biodiversity increased with the ability to convert acetate and lactate to butyrate. The MC processing exclusively lactate and acetate showed the highest biodiversity and was dominated by Clostridium (especially Clostridium_sensu_stricto_12). LAB were reduced; other genera such as Terrisporobacter, Lachnoclostridium, Paraclostridium or Sutterella were found. Butyrate was the main metabolite and pH was 7. Shotgun metagenomic analysis of the selected butyrate-producing MCs independently on the substrate revealed C.tyrobutyricum as the dominant Clostridium species. Functional analysis confirmed the presence of genes encoding key enzymes of the fermentation routes. Conclusions Batch tests revealed the dynamics of metabolic activity and composition of DF-MCs dependent on fermentation conditions. The balance between LAB and the butyrate producers and the pH values were shown to be the most relevant for the process of lactate and acetate conversion to butyrate. To close the knowledge gaps is to find signalling factors responsible for the metabolic shift of the DF-MCs towards lactate fermentation.
- Published
- 2021