Methanogen

About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.

Dynamics of Microbial Populations Responsible for Biodegradation during the Full-Scale Treatment of Palm Oil Mill Effluent

Abstract: Despite efforts to address the composition of the microbial community during the anaerobic treatment of palm oil mill effluent (POME), its composition in relation to biodegradation in the full-scale treatment system has not yet been extensively examined. Therefore, a thorough analysis of bacterial and archaeal communities was performed in the present study using MiSeq sequencing at the different stages of the POME treatment, which comprised anaerobic as well as facultative anaerobic and aerobic processes, including the mixed raw effluent (MRE), mixing pond, holding tank, and final discharge phases. Based on the results obtained, the following biodegradation processes were suggested to occur at the different treatment stages: (1) Lactobacillaceae (35.9%) dominated the first stage, which contributed to high lactic acid production; (2) the higher population of Clostridiaceae in the mixing pond (47.7%) and Prevotellaceae in the holding tank (49.7%) promoted acetic acid production; (3) the aceticlastic methanogen Methanosaetaceae (0.6-0.8%) played a role in acetic acid degradation in the open digester and closed reactor for methane generation; (4) Syntrophomonas (21.5-29.2%) appeared to be involved in the degradation of fatty acids and acetic acid by syntrophic cooperation with the hydrogenotrophic methanogen, Methanobacteriaceae (0.6-1.3%); and (5) the phenols and alcohols detected in the early phases, but not in the final discharge phase, indicated the successful degradation of lignocellulosic materials. The present results contribute to a better understanding of the biodegradation mechanisms involved in the different stages of the full-scale treatment of POME.

Effect of metal nanoparticles on microbial community shift and syntrophic metabolism during anaerobic digestion of Azolla microphylla

Abstract: Supplementation of anaerobic digesters with conductive nanoparticles (NPs) is considered as a potential approach for augmenting methanogenesis, however, their impact on microbial diversity, methanogenesis routes and metabolic pathways appear to differ depending on the substrate and operational conditions. Hence, in the present study, using metagenomics and KEGG pathway analysis, an attempt was made to gain an insight into the influence of two NPs viz., Fe3O4 and Ni, on the microbial composition and metabolic pathways during anaerobic digestion (AD) of Azolla microphylla. Results showed that addition of both Fe3O4 and Ni NPs at optimal concentration significantly accelerated the substrate degradation rate (89.8%) thereby enhancing the biomethane yield by 49.1% in anaerobic reactor (M3) supplemented with NPs as compared to control (M0). The dominance of microbial species (Enterococcus sp.) belonging to Firmicutes phylum in M3 reactor, indicated an efficient hydrolysis of Azolla biomass, owing to abundance of glycoside hydrolase (GH)-coding genes in their genome. Metagenomic analysis showed the enrichment of Geobacter sp. and Methanosaeta harundinacea in NPs-amended reactor confirming syntrophic metabolism of AD intermediate products that could have resulted in enhanced hydrogenotrophic methanogenesis via DIET. Predominance of Fe (III) reducing acetoclastic methanogen Methanosarcina acetivorans in NPs-fed reactor might also have been attributed to enhanced methane production. KEGG pathway analysis also showed an enhancement of major metabolic pathways viz., Carbohydrate metabolism, Methane metabolism and Lipid metabolism, in M3 reactor which further signifies the stimulatory effect of NPs.

Development of droplet digital PCR assays for methanogenic taxa and examination of methanogen communities in full-scale anaerobic digesters.

Abstract: Droplet digital PCR (ddPCR) is a new DNA quantification platform without an external DNA calibrator. This study examined methanogen communities in four full-scale anaerobic digesters treating municipal sewage sludge, using ddPCR with taxon-specific primer/TaqMan probe sets (5 orders, 11 families, and 13 genera), many of which were developed in this study. Total methanogen abundance was positively correlated with hydraulic retention time (HRT) and temperature (p < 0.05), though the effect of HRT was stronger (r = 0.864 vs. 0.682, respectively). Moreover, total abundance was strongly correlated with biogas production rate (r = 0.896). HRT was positively correlated with seven methanogenic taxa, while temperature was positively or negatively correlated with 13 taxa (p < 0.05). For instance, the predominant genera Methanosaeta and Methanosarcina were negatively and positively associated, respectively, with temperature only (p < 0.05). Redundancy analysis and principal component analysis using the absolute-abundance dataset indicated that only temperature explained the variability in the methanogen communities at all classification levels. Therefore, HRT was the most important operational factor to influence net methanogen abundance and activity, while temperature governed the composition of the methanogen community. ddPCR enabled absolute quantification of methanogens without the external DNA standards and linked methanogen communities and operational factors, suggesting that it is a promising tool for analyzing the microbial ecology of anaerobic digestion.