University of Innsbruck
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 Austrian Science Fund project Phenylomicrobe 

The role of anaerobic microorganisms during phenyl acid turnover in methanogenic systems

Start of the project


Principal Investigator

Andreas O. Wagner

Research context

The progressively improved exploitation of the chemically bound energy in substrates designated for anaerobic digestion (AD) increased both biogas yields and the risk of undesired by-product formation due to improved substrate disintegration. Phenyl acids (PAs) like phenylacetate,
-propionate and/or -butyrate exert a negative effect on AD processes; however, detailed information about the inhibitory effects of these aromatic compounds on methanogenic microbiomes is still missing.


The impact of PAs on methanogenic systems in general and on methanogenesis and acetogenesis in particular is not sufficiently studied. Strategies to manage PA accumulation are missing and knowledge on PA-utilizing pure or mixed cultures is still pending. These data are necessary to better understand the effects of PAs on the complex microbial interactions during AD.


In anaerobic digestion systems, the effect of PAs on microorganisms can partly be compensated due to functional redundancies within the microbiome. However, single and co-cultures, associated with acetogenesis and methanogenesis, are restricted to a small pool of biochemical reactions and are thus more likely affected by PAs. Parameters like temperature or pH can significantly impact these effects.

Alternative terminal electron acceptors (TEAs) – applied in an appropriate concentration – can reverse the accumulation of PAs in AD systems.

Cultures comprised of only few microorganisms are able to completely degrade PAs and thus generate methane and carbon dioxide out of these compounds.


Profound knowledge on the effects of PAs on different phases of anaerobic digestion in general as well as on methanogenic and acetogenic microorganisms in particular.

Evaluation of the effects of different alternative TEAs on PA accumulation / degradation dynamics thus on microorganisms engaged in the PA turn-over.

As we see a need for cultivation in general and for generation of pure cultures in particular, the project additionally aims at generating and investigating pure and/or co-cultures. These cultures – some were already generated in a previous project – will be used to elucidate i) which anaerobic organisms are involved in the mineralization of PAs, ii) which (syntrophic) interactions / dependencies are necessary to fully degrade PAs, and iii) which intermediates / end-products emerge and, thus, which degradation pathways are involved.


A mix of analytical, microbiological, and highly modern molecular techniques (for DNA and RNA) will be applied. This includes (but is not limited to) the use of GC, HPLC analyses, fluorescence-spectrophotometry,  anaerobic cultivation procedures, 16S rRNA amplicon sequencing, shot-gun sequencing, metatranscriptomics, qPCR / dPCR, and bioinformatics data analyses.

Prem, E. M.; Duschl, S. F.; Wagner, A. O. (2023): Effects of increasing phenyl acid concentrations on the AD process of a multiple-biogas-reactor system. In: Biomass and Bioenergy 168C, 2023, 106686. DOI: 10.1016/j.biombioe.2022.106686

Prem, E.M.; Schwarzenberger, A.; Markt, R.; Wagner, A. O. (2023): Effects of phenyl acids on different degradation phases during thermophilic anaerobic digestion. In: Frontiers in Microbiology 14, Artikel 1087043. DOI: 10.3389/fmicb.2023.1087043.

Prem E.M.; Wagner A.O.: Microbial and phenyl acid dynamics during the start-up phase of anaerobic straw degradation in meso- and thermophilic batch reactors. International Conference on Biogas Microbiology, Braga, Portugal, May 2022.

Wunderer M.; Prem E.M.; Wagner, A.O.: The impact of phenyl acids on methanogenic pure cultures. International Conference on Biogas Microbiology, Braga, Portugal, May2022. 

Prem E.M.; Wunderer M.; Markt R.; Wagner A.O.: Effects of phenyl acids on the active AD community at different pH conditions. Conference on Monitoring Process Control of Anaerobic Digestion Processes, Leipzig, Germany, March 2023.

Wunderer M.; Mullaymeri A.; Schmiedhofer A.; Prem E.M.; Wagner A.O.: Effects of phenyl acids on aceto- and methanogenesis. 12th International Symposium on Anaerobic Microbiology, Innsbruck, Austria, May 2023.

Prem E.M.; Schwarzenberger, A.; Markt, R.; Wagner, A.O.: Effects of phenyl acids on different degradation phases during thermophilic anaerobic digestion, 12th International Symposium on Anaerobic Microbiology, Innsbruck, Austria, May 2023

Andreas O. Wagner, Dep. of Microbiology, Univ. Innsbruck

Eva M. Prem, Dep. of Microbiology, Univ. Innsbruck

Mathias Wunderer, Dep. of Microbiology, Univ. Innsbruck

Katherina O. Fliegerova, Inst. of Animal Physiology, Academy of Science CZ

Blaz Strez, Dep. of Animal Science, Univ. of Ljubljana

Eva Maria Prem

Title: Effects of Inhibitory Substances on the Anaerobic Degradation of Organic Materials – Investigation of Impaired Methanogenic Fermentation System

2017 - 2022

Mathias Wunderer

Title: Role of Anaerobic Microorganisms During Degradation of Phenyl Acids in Methanogenic Systems

2020 -

Simon Franz Duschl

Title: Establishment of an thermophilic, parallel, semi-continuous reactor system for analysing increasing phenyl acid concentrations during AD

Finished: 2021

Julia Rothärmel

Title: Effects of phenyl acids on the 4 degradation steps during mesophilic AD

Finished: 2022

Christian Scherfler

Title: Establishment and start-up of an mesophilic biogas reactor system for testing the effects of increasing concentrations of phenyl acids during AD

Finished: 2022

Katharina Haberditz

Title: Degradation of phenyl acid in the presence of alternative electron acceptors

Finished: 2022

Alen Simonic

Title: Effects of phenyl acid pulses on anaerobic digestion and biogas production under thermophilic conditions

Finished: 2023

Anna Kammerer

Title: Occurrence and performance of syntrophic acetate oxidizing bacteria (SAOBs) during anaerobic degradation of aromatic compounds in thermophilic systems

Finished: 2023

Andja Mullaymeri

Title: Effects of phenyl acids on the acetoclastic methanogens Methanosarcina acetovorans and Methanosarcina thermophila

2022 - 2023

Anna Schmiedhofer

Title: Effects of phenyl acids on the acetoclastic methanogens Methanoculleus thermophilus and Methanocella arvoryzae

2022 - 2023

Martin Unterkircher

Title: Effects of phenyl acids on the hydrogenotrophic methanogen Methanothermobacter wolfeii and on the metylotrophic methanogen Methanomethylovorans thermophila 

2023 - 

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