Methanogen

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

Biostimulation by direct voltage to enhance anaerobic digestion of waste activated sludge

Abstract: Electrical stimulation has been used conventionally for stimulation of microorganisms, and also be a promising technology to manage wastewater treatment by stimulating microbial metabolism. Previous studies on electrical stimulation were mainly focused on sewage treatment and groundwater purification, while little attention has been paid to its effect on anaerobic digestion of waste activated sludge (WAS). In this study, different voltages (0.3–1.5 V) were applied to investigate the influence of electrical stimulation on the anaerobic digestion of WAS. The results revealed that applied voltages could accelerate sludge hydrolysis and acidification process. The best performance in terms of methane production and sludge reduction was obtained with the applied voltage of 0.6 V. In this case, methane production increased by 76.2% with an enhanced VS removal rate (26.6%) compared to the control group. The energy consumption at 0.6 V could be neglected compared to the incremental energy generated from the methane. However, methane production decreased and hydrogen was produced when the applied voltage increased to 0.9 V. At higher voltages (1.2 V and 1.5 V), more soluble organic matters were released. In particular, the VFAs concentration peaked at 640 mg L−1 and 1001 mg L−1, respectively. Pyrosequencing revealed that hydrogenotrophic methanogens consisted majority of methanogen population when the applied voltage was over 0.6 V, while acetoclastic methanogens showed overwhelming dominance at 0.3 V. Moreover, 0.6 V enriched Pseudomonas for protein degradation and Methanoregula for methane generation with species richnesses of 19.1% and 53.3%, respectively.

Microbial composition and characterization of prevalent methanogens and acetogens isolated from syntrophic methanogenic granules

Abstract: The microbial species composition of methanogenic granules developed on an acetate-propionate-butyrate mixture was characterized. The granules contained high numbers of adhesive methanogens (1012/g dry weight) and butyrate-, isobutyrate-, and propionate-degrading syntrophic acetogens (1011/g dry weight), but low numbers of hydrolytic-fermentative bacteria (109/g dry weight). Prevalent methanogens in the granules included: Methanobacterium formicicum strain T1N and RF, Methanosarcina mazei strain T18, Methanospirillum hungatei strain BD, and a non-filamentous, bamboo-shaped rod species, Methanothrix/Methanosaeta-like strain M7. Prevalent syntrophic acetogens included: a butyrate-degrading Syntrophospora bryantii-like strain BH, a butyrate-isobutyrate degrading non-spore-forming rod, strain IB, a propionate-degrading sporeforming oval-shaped species, strain PT, and a propionate-degrading none-spore-forming sulfate-reducing rod species, strain PW, which was able to grow syntrophically with an H2-utilizing methanogen. Sulfate-reducing bacteria did not play a significant role in the metabolism of H2, formate, acetate and butyrate but they were involved in propionate degradation.

Methanogenesis in an Upflow Anaerobic Sludge Blanket Reactor at pH 6 on an Acetate-Propionate Mixture

Abstract: High-rate anaerobic digestion can be applied in upflow anaerobic sludge blanket reactors for the treatment of various wastewaters. In upflow anaerobic sludge blanket reactors, sludge retention time is increased by a natural immobilization mechanism (viz. the formation of a granular type of sludge). When this sludge is cultivated on acid-containing wastewater, the granules mainly consist of an acetoclastic methanogen resembling Methanothrix soehngenii. This organism grows either in rods or in long filaments. Attempts to cultivate a stable sludge consisting predominantly of Methanosarcina sp. on an acetate-propionate mixture as substrate by lowering the pH from 7.5 during the start-up to approximately 6 failed. After 140 days of continuous operation of the reactor a filamentous organism resembling Methanothrix soehngenii prevailed in the sludge. The specific methanogenic activity of this sludge on acetate-propionate was optimal at pH 6.6 to 6.8 and 7.0 to 7.2, respectively.

Conversion of Methanol and Methylamines to Methane and Carbon Dioxide

Abstract: The first report on methane formation from a methylated one-carbon compound, notably methanol, goes back to 1920 (Groenewegen, 1920). In the thirties, methylotrophic methanogens were systematically studied in the laboratory of Kluy ver and Van Niel (1936). Here, Barker (1936) enriched an organism, then called Methanococcus mazei, which was capable of growth not only on methanol, but also on butanol and acetone. The organism was not pure and the original cultures were lost. Only about 40 years later, the methanogen that met the original description was reisolated and renamed Methanosarcina mazei (Mah, 1980; Mah and Kuhn, 1984). The first methylotroph obtained in axenic culture, and in fact one of the first pure methanogenic species, was isolated by Schnellen (1936), a student of Kluyver. Again, the original cultures of the organism, Methanosarcina barkeri, were lost. M. barkeri has been reisolated as a number of distinct strains from a variety of sources. The type strain, MS, was obtained by Bryant in 1966 (Bryant, 1966; Bryant and Boone, 1987). Biochemically, M. barkeri is the best studied methylotrophic methanogen and most of the work reviewed in this chapter refers to it.

Microbial community of a mesophilic propionate-degrading methanogenic consortium in chemostat cultivation analyzed based on 16S rRNA and acetate kinase genes.

Abstract: We constructed a mesophilic anaerobic chemostat that was continuously fed with synthetic wastewater containing propionate as the sole source of carbon and energy. Steady-state conditions were achieved below the critical dilution rate of 0.3 d −1 with almost complete substrate degradation. The propionate-degrading methanogenic communities in the chemostat at dilution rates of 0.01, 0.08, and 0.3 d −1 were analyzed using molecular biological techniques. Fluorescence in situ hybridization with archaeal and bacterial domain-specific probes showed that archaeal cells predominated throughout the three dilution rates. Archaeal-16S rRNA gene clone library analysis and quantitative real-time polymerase chain reaction studies showed that hydrogenotrophic methanogen rRNA genes closely related to Methanoculleus was detected at a dilution rate of 0.01 d −1 , whereas rRNA genes closely related to the Methanoculleus and Methanospirillum genera were detected at dilution rates of 0.08 and 0.3 d −1 . The aceticlastic methanogen, Methanosaeta , was detected throughout the three dilution rates. Bacterial-rRNA gene clone library analysis and denaturing gradient gel electrophoresis demonstrated that rRNA genes affiliated with the genus Syntrophobacter predominated at the low dilution rate, whereas rRNA genes affiliated with the phylum Firmicutes predominated at the higher dilution rates. A significant number of rRNA genes affiliated with the genus Pelotomaculum were detected at dilution rate of 0.3 d −1 . The diversity of genes encoding acetate kinase agreed closely with the results of the rRNA gene analysis. The dilution rates significantly altered the archaeal and bacterial communities in the propionate-fed chemostat.