Biogas production: evaluation of the influence of K₂FeO₄ pretreatment of maple leaves (Acer platanoides) on microbial consortia composition

The potential of K₂FeO₄ as a pretreatment agent of a lignocellulosic material was examined on leaves of Acer platanodides as the sole substrate for biogas production by anaerobic digestion carried out through modelling laboratory-scaled semi-continuous reactors differing in loading rates and substrate (pretreated and untreated leaves). The quality of bioagas produced by K₂FeO₄-pretreated leaves was significantly better in terms of higher methane content and lower content of H₂S. K₂FeO₄ had no crucial influence on growth inhibition of biogas-producing bacteria, which were analysed by comprehensive culture-independent methods utilising high-throughput sequencing of specific genes [bacterial and archaeal 16S rRNA, formyltetrahydrofolate synthetase gene (fhs), methyl-coenzyme M reductase α subunit gene (mcrA) and fungal internal transcribed spacers (ITS)]. The higher amount of CH₄ in biogas utilising pretreated leaves as substrate could be caused by a shift to acetoclastic methanogenesis pathway, which was indicated by the higher amount of homoacetogenic bacteria and acetotrophic methanogens detected in those reactors.