Presence and transcriptional activity of anaerobic fungi in agricultural biogas plants

Abstract

Bioaugmentation with anaerobic fungi (AF) is promising for improved biogas generation from lignocelluloses-rich substrates. However, before implementing AF into biogas processes it is necessary to investigate their natural occurrence, community structure and transcriptional activity in agricultural biogas plants. Thus, AF were detected with three specific PCR based methods: (i) Copies of their 18S genes were found in 7 of 10 biogas plants. (ii) Transcripts of a GH5 endoglucanase gene were present at low level in two digesters, indicating transcriptional cellulolytic activity of AF. (iii) Phylogeny of the AF-community was inferred with the 28S gene. A new Piromyces species was isolated from a PCR-positive digester. Evidence for AF was only found in biogas plants operated with high proportions of animal feces. Thus, AF were most likely transferred into digesters with animal derived substrates. Additionally, high process temperatures in combination with long retention times seemed to impede AF survival and activity.

Different response of bacteria, archaea and fungi to process parameters in nine full‐scale anaerobic digesters

“…There are only few reports about fungi in anaerobic reactors (Ritari et al ., ; Bengelsdorf et al ., ; Kazda et al ., ; Dollhofer et al ., ; Young et al ., ). Fungal ribosomal rRNA from an astonishing variety of taxa ( Ascomycota and Basidiomycota ) was found in the present study.…”

“…In recent years, much more attention was paid to transcriptomic and proteomic approaches (for reviews see Heyer et al, 2016;Hassa et al, 2018). However, studies targeting the 16S rRNA of bacteria, archaea and 28S rRNA of fungi, respectively, are rare for anaerobic reactors (Lebuhn et al, 2014;De Vrieze et al, 2016;Dollhofer et al, 2017). The applied PCoA showed remarkable resemblances of the microbial communities in the analysed full-scale anaerobic digesters (Fig.…”

“…However, the study by Dollhofer et al . () did not consider facultative anaerobic fungi. The presence of facultative anaerobic fungi in anaerobic digesters has been mainly investigated by means of DNA sequencing (Ritari et al ., ; Bengelsdorf et al ., ; Kazda et al ., ).…”

“…Still, the presence and function of active fungi in anaerobic digesters have been barely investigated. Dollhofer et al (2017) showed the presence of obligate anaerobic fungi (Neocallimastigomycota) in 7 of 10 agricultural biogas plants. Transcriptional cellulolytic activity of these fungi could only be detected in two of these biogas plants (Dollhofer et al, 2017).…”

“…Thereafter, bacterial cells have access to plant tissues for further enzymatic degradation of cellulose and hemicellulose fractions. However, the study by Dollhofer et al (2017) did not consider facultative anaerobic fungi. The presence of facultative anaerobic fungi in anaerobic digesters has been mainly investigated by means of DNA sequencing (Ritari et al, 2012;Bengelsdorf et al, 2013;Kazda et al, 2014).…”