Dynamics of dark fermentation microbial communities in the light of lactate and butyrate production

Abstract Background This study focuses on the processes occurring during acidogenic step of anaerobic digestion, especially resulting from nutritional interactions between dark fermentation (DF) bacteria and lactic acid (LAB). Previously, we have confirmed that DF microbial communities (MCs) fed molasses are able to convert lactate acetate butyrate. The aims were recognize biodiversity DF-MCs unable butyrate define conditions for transformation. Results MCs sampled a bioreactor grown anaerobically in mesophilic different media containing or sucrose and/or five independent static batch experiments. taxonomic composition (based 16S_rRNA profiling) each experimental MC was analysed reference its metabolites pH digestive liquids. In samples where fermented contained carbohydrates, two main tendencies observed: (i) low (pH ? 4), ethanol as products, dominated with Lactobacillus , Bifidobacterium Leuconostoc Fructobacillus characterized by biodiversity; (ii) range 5.0–6.0, among composed mainly Clostridium (especially Clostridium_ sensu_stricto_12), Prevotella. increased ability processing exclusively showed highest sensu_stricto_12). LAB reduced; other genera such Terrisporobacter Lachnoclostridium Paraclostridium Sutterella found. Butyrate metabolite 7. Shotgun metagenomic analysis selected butyrate-producing independently substrate revealed C.tyrobutyricum dominant species. Functional presence genes encoding key enzymes routes. Conclusions Batch tests dynamics metabolic activity dependent conditions. balance producers values shown be most relevant process conversion To close knowledge gaps is find signalling factors responsible shift towards fermentation.