Iron zero valent nanoparticles applied in the biorefinery concept: Functional genes in continuous bioreactor fermenting vinasse

Increased production of biogas and volatile acids was evaluated by the addition of Fe0 Nanoparticles (NP) on Anaerobic Fluidized Bed Reactor (AFBR-NP) with expanded clay as support material (45.1 mg Fe0 g−1 expanded clay), fermenting vinasse, and operated at 37 °C and 3h Hydraulic Retention Time (HRT). Higher H2 percentage in the biogas composition was observed in AFBR-NP (50–65%) when compared to AFBR without NP, AFBR-Control (24–43%). A 1.2-fold higher valeric acid production was also observed as a result of NPs supplementation. Genes related to the first steps of vinasse anaerobic degradation in AFBR-NP (beta-glucosidase, glucokinase and pyruvate-ferredoxin oxidoreductase) and the genes related to volatile acids production (L- and d-lactate dehydrogenase, 3-hydroxybutyryl-CoA dehydrogenase, acetate kinase, pyruvate kinase and fumarate reductase flavoprotein) were observed by metagenome sequencing. A 4.2-fold higher relative abundance of Secundilactobacillus genus in AFBR-NP was evidenced. The genetic and microbial community differences observed with the addition of NP resulted in improved biorefinery products of anaerobic digestion.