Evaluation of stable isotope fingerprinting techniques for the assessment of the predominant methanogenic pathways in anaerobic digesters

Abstract

Laboratory biogas reactors were operated under various conditions using maize silage, chicken manure, or distillers grains as substrate. In addition to the standard process parameters, the hydrogen and carbon stable isotopic composition of biogas was analyzed to estimate the predominant methanogenic pathways as a potential process control tool. The isotopic fingerprinting technique was evaluated by parallel analysis of mcrA genes and their transcripts to study the diversity and activity of methanogens. The dominant hydrogenotrophs were Methanomicrobiales, while aceticlastic methanogens were represented by Methanosaeta and Methanosarcina at low and high organic loading rates, respectively. Major changes in the relative abundance of mcrA transcripts were observed compared to the results obtained from DNA level. In agreement with the molecular results, the isotope data suggested the predominance of the hydrogenotrophic pathway in one reactor fed with chicken manure, while both pathways were important in the other reactors. Short-term changes in the isotopic composition were followed, and a significant change in isotope values was observed after feeding a reactor digesting maize silage. This ability of stable isotope fingerprinting to follow short-term activity changes shows potential for indicating process failures and makes it a promising technology for process control.

Methanogenic community composition in an organic waste mixture in an anaerobic bioreactor

“…In total, six characteristics of terminal restriction fragments (T-RFs) were detected as major peaks in electrophoresis. The detected t-RFs can be assigned to the following genera: Methanosaeta, Methanoculleus, Methanobacterium, Methanobrevibacter, Methanosarcina and Methanospirillum, which is consistent with the previous study by Nikolausz et al (2013).…”

“…67, 24.2, 32.17, 39.77, 38.50, 22.77, 68.84, 27.80 ng/ µl for samples FM1, FM2, FM3, FM4, FM5, FM6, FM7 and FM8, respectively. The mcrA gene was amplified via PCR using a pair of primers: the mcrA-specific forward primer mlas (5'-GGT GGT GTM GGD TTC ACM CAR TA-3') and the reverse primer mcrA-rev (5'-CGT TCA TBG CGT AGT TVG GRT AGT-3') (Nikolausz et al, 2013). The reverse primer was 5'-labelled with the phosphoramidite fluorochrome 6-carboxyfluorescein (6-FAM).…”

“…There are a few scientific reports (Enitan et al, 2014;Esposito et al, 2012;Nikolausz et al, 2013) that have collated the microbial consortium involved in anaerobic digestion for precise characterisation and comparison to the methane yield efficiency derived from each stage consortium. We hypothesise that gaining a data set on the methanogen composition using metagenomic tools and comparing it with the potential effectiveness of their activity will identify the essential step and methanogens involved in it, which will affect biogas profitability.…”

Agricultural biogas production in Germany - from practice to microbiology basics

“…H 2 and formate are of outstanding importance in electron transfer between syntrophic donor bacteria and the accepting methanogens [32,33,44,45]. Along with syntrophic oxidation of other process intermediates, syntrophic acetate oxidation (SAO) was shown by results of different approaches to prevail in high throughput biogas processes, high-performance biogas plants particularly at high temperature and at high ammonia concentration [46][47][48][49][50][51][52]. The predominance of SAO in these processes is in contradiction to various textbooks assigning 70% of the methane to be produced by acetate splitting and only 30% via the hydrogenotrophic pathway.…”

“…Very few Methanosaeta sequences were found only in the mesophilic maize digesters. Acetate splitting and members of this strictly acetoclastic genus are typically found at low acetate and NH 3 concentration and high microbial retention time [31,[50][51][52]59]. Methanococci and Methanopyri, typically thriving in very hot environments, and anaerobic methane oxidizers were not recovered.…”