Metatranscriptomic analysis of an acidogenic reactor reveals degradation pathways of sugarcane vinasse-compounds and associated microbiome

Sugarcane vinasse is a high-strength wastewater from ethanol distillation. It can be anaerobically biodegraded, yielding methane and intermediary metabolites as valuable byproducts. In this study, metabolic pathways and associated microbiome from an acidogenic reactor was investigated through metatranscriptomics, comparing three stages of operation: 100% sucrose-based substrate (SBS), 50% SBS and 50% vinasse, 100% vinasse. Under sucrose feeding, pH dropped to pH 2.7, Ethanoligenens and Clostridium were linked to biohydrogen production. As vinasse was added, pH increased to 4.1-4.5, resulting in a shift of the active microorganisms. With vinasse as substrate, Pectinatus, Prevotella and Megasphaera were the main genera assigned to carbohydrate metabolism, Pectinatus and Prevotella to glycerol degradation, Pectinatus to sulfate reduction. Considering the three stages of operation, acetate was produced especially by Ethanoligenens, Clostridium, Liquorilactobacillus and Megasphaera, butyrate by Clostridium and Megasphaera, propionate by Pectinatus. These results can be of great relevance to understand and optimize anaerobic digestion processes towards the desirable products.