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15 pages, 2898 KiB

Open AccessArticle

Comparison of Various Reducing Agents for Methane Production by Methanothermobacter marburgensis

by Maximilian Peter Mock, Rayen Ochi, Maria Bieringer, Tim Bieringer, Raimund Brotsack and Stephan Leyer

Microorganisms 2023, 11(10), 2533; https://doi.org/10.3390/microorganisms11102533 - 10 Oct 2023

Cited by 2 | Viewed by 2591

Abstract

Biological methanation is driven by anaerobic methanogenic archaea, cultivated in different media, which consist of multiple macro and micro nutrients. In addition, a reducing agent is needed to lower the oxidation–reduction potential (ORP) and enable the growth of oxygen-sensitive organisms. Until now, sodium sulfide (Na₂S) has been used mainly for this purpose based on earlier published articles at the beginning of anaerobic microbiology research. In a continuation of earlier investigations, in this study, the usage of alternative reducing agents like sodium dithionite (Na₂S₂O₄) and L-Cysteine-HCl shows that similar results can be obtained with fewer environmental and hazardous impacts. Therefore, a newly developed comparison method was used for the cultivation of Methanothermobacter marburgensis. The median methane evolution rate (MER) for the alternatives was similar compared to Na₂S at different concentrations (0.5, 0.25 and 0.1 g/L). However, the use of 0.25 g/L Na₂S₂O₄ or 0.1 g/L L-Cys-HCl led to stable MER values over consecutive batches compared to Na₂S. It was also shown that a lower concentration of reducing agent leads to a higher MER. In conclusion, Na₂S₂O₄ or L-Cys-HCl can be used as a non-corrosive and non-toxic reducing agent for ex situ biological methanation. Economically, Na₂S₂O₄ is cheaper, which is particularly interesting for scale-up purposes. Full article

(This article belongs to the Special Issue Microorganisms in Biomass Conversion and Biofuel Production)

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16 pages, 5812 KiB

Open AccessArticle

Quantitative Analysis of Core Lipid Production in Methanothermobacter marburgensis at Different Scales

by Lydia M. F. Baumann, Ruth-Sophie Taubner, Kinga Oláh, Ann-Cathrin Rohrweber, Bernhard Schuster, Daniel Birgel and Simon K.-M. R. Rittmann

Bioengineering 2022, 9(4), 169; https://doi.org/10.3390/bioengineering9040169 - 10 Apr 2022

Cited by 3 | Viewed by 2934

Abstract

Archaeal lipids have a high biotechnological potential, caused by their high resistance to oxidative stress, extreme pH values and temperatures, as well as their ability to withstand phospholipases. Further, methanogens, a specific group of archaea, are already well-established in the field of biotechnology because of their ability to use carbon dioxide and molecular hydrogen or organic substrates. In this study, we show the potential of the model organism Methanothermobacter marburgensis to act both as a carbon dioxide based biological methane producer and as a potential supplier of archaeal lipids. Different cultivation settings were tested to gain an insight into the optimal conditions to produce specific core lipids. The study shows that up-scaling at a constant particle number (n/n = const.) seems to be a promising approach. Further optimizations regarding the length and number of the incubation periods and the ratio of the interaction area to the total liquid volume are necessary for scaling these settings for industrial purposes. Full article

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12 pages, 1356 KiB

Open AccessFeature PaperArticle

Methanogens Diversity during Anaerobic Sewage Sludge Stabilization and the Effect of Temperature

by Tomáš Vítěz, David Novák, Jan Lochman and Monika Vítězová

Processes 2020, 8(7), 822; https://doi.org/10.3390/pr8070822 - 12 Jul 2020

Cited by 12 | Viewed by 3887

Abstract

Anaerobic sludge stabilization is a commonly used technology. Most fermenters are operated at a mesophilic temperature regime. Modern trends in waste management aim to minimize waste generation. One of the strategies can be achieved by anaerobically stabilizing the sludge by raising the temperature. Higher temperatures will allow faster decomposition of organic matter, shortening the retention time, and increasing biogas production. This work is focused on the description of changes in the community of methanogenic microorganisms at different temperatures during the sludge stabilization. At higher temperatures, biogas contained a higher percentage of methane, however, there was an undesirable accumulation of ammonia in the fermenter. Representatives of the hydrogenotrophic genus Methanoliea were described at all temperatures tested. At temperatures up to 50 °C, a significant proportion of methanogens were also formed by acetoclastic representatives of Methanosaeta sp. and acetoclastic representatives of the order Methanosarcinales. The composition of methanogens in the fermenter significantly changed at 60 °C when typically thermophilic species, like Methanothermobacter marburgensis, appeared. A decrease in the diversity of methanogens was observed, and typical hydrogenotrophic methanogenic archaea isolated from fermenters of biogas plants and anaerobic wastewater treatment plants represented by genus Methanoculleus were no longer present. Full article

(This article belongs to the Special Issue Application of Microorganisms in Wastewater Treatment)

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10 pages, 518 KiB

Open AccessArticle

Effect of N₂ on Biological Methanation in a Continuous Stirred-Tank Reactor with Methanothermobacter marburgensis

by Marc Philippe Hoffarth, Timo Broeker and Jan Schneider

Fermentation 2019, 5(3), 56; https://doi.org/10.3390/fermentation5030056 - 2 Jul 2019

Cited by 7 | Viewed by 5671

Abstract

In this contribution, the effect of the presence of a presumed inert gas like

N_{2}

in the feed gas on the biological methanation of hydrogen and carbon dioxide with Methanothermobacter marburgensis was investigated.

N_{2}

can be found as a component besides [...] Read more.

In this contribution, the effect of the presence of a presumed inert gas like

N_{2}

in the feed gas on the biological methanation of hydrogen and carbon dioxide with Methanothermobacter marburgensis was investigated.

N_{2}

can be found as a component besides

{CO}_{2}

in possible feed gases like mine gas, weak gas, or steel mill gas. To determine whether there is an effect on the biological methanation of

{CO}_{2}

and

H_{2}

from renewable sources or not, the process was investigated using feed gases containing

{CO}_{2}

H_{2}

, and

N_{2}

in different ratios, depending on the

{CO}_{2}

content. A possible effect can be a lowered conversion rate of

{CO}_{2}

and

H_{2}

{CH}_{4}

. Feed gases containing up to 47%

N_{2}

were investigated. The conversion of hydrogen and carbon dioxide was possible with a conversion rate of up to 91% but was limited by the amount of

H_{2}

when feeding a stoichiometric ratio of 4:1 and not by adding

N_{2}

to the feed gas. Full article

(This article belongs to the Special Issue Biomass Conversion: Fermentation Chemicals and Fuels)

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