Long-term monitoring reveals stable and remarkably similar microbial communities in parallel full-scale biogas reactors digesting energy crops

Abstract

Biogas is an important renewable energy carrier. It is a product of stepwise anaerobic degradation of organic materials by highly diverse microbial communities forming complex interlinking metabolic networks. Knowledge about the microbial background of long-term stable process performance in full-scale reactors is crucial for rationally improving the efficiency and reliability of biogas plants. To generate such knowledge, in the present study three parallel mesophilic full-scale reactors fed exclusively with energy crops were sampled weekly over one year. Physicochemical process parameters were determined and the microbial communities were analysed by terminal restriction fragment length polymorphism (T-RFLP) fingerprinting and 454-amplicon sequencing. For investigating the methanogenic community, a high-resolution T-RFLP approach based on the mcrA gene was developed by selecting restriction enzymes with improved taxonomic resolution compared to previous studies. Interestingly, no Methanosarcina-related generalists, but rather specialized hydrogenotrophic and acetoclastic methanogenic taxa were detected. In general, the microbial communities in the non-connected reactors were remarkably stable and highly similar indicating that identical environmental and process parameters resulted in identical microbial assemblages and dynamics. Practical implications such as flexible operation schemes comprising controlled variations of process parameters for an efficient microbial resource management under fluctuating process conditions are discussed.

Inhibitory Effect of Coumarin on Syntrophic Fatty Acid-Oxidizing and Methanogenic Cultures and Biogas Reactor Microbiomes

“…Raw sequence data were processed with QIIME 1.9.1 Virtual Box release (37), according to Lucas and colleagues (38), using the 97% identity threshold for clustering into operational taxonomic units (OTUs). Chimeric sequences of mcrA genes were identified by de novo check using USEARCH (39).…”

Trace Elements Induce Predominance among Methanogenic Activity in Anaerobic Digestion

“…The T-RFLP analysis of bacterial and methanogenic communities using FAM-labeled PCR products was done as described previously (Sträuber et al, 2012; Lucas et al, 2015). PCR product quality was checked by agarose gel electrophoresis and amplicons were purified with SureClean (Bioline, Luckenwalde, Germany).…”

“…Cloning, sequencing, and identification of the mcrA amplicons were conducted as described by Lucas et al (2015). The obtained partial mcrA sequences were deposited in GenBank under accession numbers KU179685-KU179691.…”

Changing Feeding Regimes To Demonstrate Flexible Biogas Production: Effects on Process Performance, Microbial Community Structure, and Methanogenesis Pathways

“…More frequent feeding is usually preferred in the conventional operation of biogas plants, because in common practice it is believed to help the stability of the process (6). A change from more to less frequent feeding at the same organic loading rate (OLR) may lead to process disturbance, such as volatile fatty acid (VFA) accumulation, a lower pH, and a mismatch between the growth rates of VFAproducing and -consuming microbes (7,8).…”