Modeling of hydrogen and organic acid production using different concentrations of sugarcane vinasse under thermophilic conditions and a link with microbial community 16S rRNA gene sequencing data

Acidogenesis of sugarcane vinasse at 15 and 20 kgCOD m(-3) in a batch bioreactor occurred via acrylate and homoacetogenesis pathways. Both these pathways were incorporated into the Anaerobic Digestion Model Number 1 (ADM1) and they were validated with biomolecular analysis. As a novelty of this work, ADM1 was modified integrating a new lactate consumption pathway to the model (Lactate -> Acetate + Propionate +Hydrogen) and the homoacetogenesis (Hydrogen + CO2 -> Acetate) to initial concentrations of vinasse of 15 and 20 kgCOD m(-3). To evaluate the microbial community involved in such fermentative pathways, biomass samples were taken from the reactor operated with vinasse under organic matter concentrations of 15, 20 and 30 kgCOD m(-3), which was analyzed by 16S rRNA gene massive sequencing. Moreover, the abundance of hydrogen producing microorganisms and homoacetogens were quantified by q-PCR. It was mathematically demonstrated that the acrylate and homoacetogenesis pathways were able to describe the system at low concentrations of sugarcane vinasse (15 and 20 kgCOD m(-3)) and the microbial community compositions confirmed the presence of microorganisms with the metabolic pathways hypothesized here.

Automated summary

This study validated the acidogenesis of sugarcane vinasse in a batch bioreactor via acrylate and homoacetogenesis pathways through biomolecular analysis and quantitative assessment of microbial communities. It also proposed an improved model that integrated a new lactate consumption pathway and homoacetogenesis to accurately describe the system.