Austrian Science Fund project Phenylomicrobe 

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

Start of the project

2020

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.

Originality

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.

Hypotheses

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.

Objectives

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.

Methods

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.