A review on the bioenergetics of anaerobic microbial metabolism close to the thermodynamic limits and its implications for digestion applications

Leng, Ling; Yang, Peixian; Singh, Shubham; Zhuang, Huichuan; Xu, Linji; Chen, Wen‐Hsing; Dolfing, Jan; Liu, Dong; Zhang, Yan; Zeng, Huiping; Chu, Wei; Lee, Po‐Heng

doi:10.1016/j.biortech.2017.09.103

Cited by 156 publications

(64 citation statements)

References 93 publications

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“…This finding is in accordance with previous studies which showed a predominance of the hydrogenotrophic pathway of methane formation under elevated TAN concentration e.g., [14,15,38,62,63]. Hydrogenotrophic archaea are also known as hydrogen scavengers, meaning they depend on H 2 which is produced by their neighboring bacteria (such as members of the genera Syntophomonas, Syntrophobacter, Syntrophus, Propionibacter, Pelotomaculum, Smithella, or Clostridium [38,39]) who in turn can only grow if the H 2 is consumed. Consequently, an inhibition of the function of hydrogenotrophic archaea by NH 4 + /NH 3 can lead to a process disturbance which is reflected not only in reduced methane yields, but also in acid accumulation as it was recorded in reactors SB-M2 and M-SB2.…”

Section: Bacterial Community At High Tan Concentrationsupporting

confidence: 92%

“…This species is able to degrade fatty acids and aromatic acids in a syntrophic relationship with hydrogenotrophic methanogens [61]. This finding is in accordance with previous studies which showed a predominance of the hydrogenotrophic pathway of methane formation under elevated TAN concentration e.g., [14,15,38,62,63]. Hydrogenotrophic archaea are also known as hydrogen scavengers, meaning they depend on H 2 which is produced by their neighboring bacteria (such as members of the genera Syntophomonas, Syntrophobacter, Syntrophus, Propionibacter, Pelotomaculum, Smithella, or Clostridium [38,39]) who in turn can only grow if the H 2 is consumed.…”

Section: Bacterial Community At High Tan Concentrationsupporting

confidence: 91%

“…Apparently, compounds in the sugar beet silage were degraded into propionic acid but the community was not capable of further conversion into biogas. This can be explained by the fact that methanogenic archaea only metabolizes acetic acid, H 2 , and one-carbon (C1) compounds; hence, fatty acids such as propionic acid first have to be converted into these utilizable compounds until biogas can be produced in syntrophic relationships [38][39][40]. However, the VFA concentration in the silage reactors (SB-M1, M-SB1) was below 0.5 g·L −1 (Figure 1a…”

Section: Chemical and Operational Parametersmentioning

confidence: 99%

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Effect of a Profound Feedstock Change on the Structure and Performance of Biogas Microbiomes

et al. 2020

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In this study the response of biogas-producing microbiomes to a profound feedstock change was investigated. The microbiomes were adapted to the digestion of either 100% sugar beet, maize silage, or of the silages with elevated amounts of total ammonium nitrogen (TAN) by adding ammonium carbonate or animal manure. The feedstock exchange resulted in a short-range decrease or increase in the biogas yields according to the level of chemical feedstock complexity. Fifteen taxa were found in all reactors and can be considered as generalists. Thirteen taxa were detected in the reactors operated with low TAN and six in the reactors with high TAN concentration. Taxa assigned to the phylum Bacteroidetes and to the order Spirochaetales increased with the exchange to sugar beet silage, indicating an affinity to easily degradable compounds. The recorded TAN-sensitive taxa (phylum Cloacimonetes) showed no specific affinity to maize or sugar beet silage. The archaeal community remained unchanged. The reported findings showed a smooth adaptation of the microbial communities, without a profound negative impact on the overall biogas production indicating that the two feedstocks, sugar beet and maize silage, potentially do not contain chemical compounds that are difficult to handle during anaerobic digestion.

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Section: Bacterial Community At High Tan Concentrationsupporting

confidence: 92%

Section: Bacterial Community At High Tan Concentrationsupporting

confidence: 91%

Section: Chemical and Operational Parametersmentioning

confidence: 99%

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Effect of a Profound Feedstock Change on the Structure and Performance of Biogas Microbiomes

et al. 2020

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“…Overloads often are related to acid accumulation (Figure 3), indicating an imbalance of microbial acid producers and consumers [40,63,68,69]. The underlying mechanism is based on different ways of obtaining energy and consequently on different growth rates: a thermodynamically more favorable energy production results in faster growth rates of the microorganisms [70][71][72][73].…”

Section: Overload Of the Microbial Degradation Potentialmentioning

confidence: 99%

Process Disturbances in Agricultural Biogas Production—Causes, Mechanisms and Effects on the Biogas Microbiome: A Review

2019

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Disturbances of the anaerobic digestion process reduce the economic and environmental performance of biogas systems. A better understanding of the highly complex process is of crucial importance in order to avoid disturbances. This review defines process disturbances as significant changes in the functionality within the microbial community leading to unacceptable and severe decreases in biogas production and requiring an active counteraction to be overcome. The main types of process disturbances in agricultural biogas production are classified as unfavorable process temperatures, fluctuations in the availability of macro- and micronutrients (feedstock variability), overload of the microbial degradation potential, process-related accumulation of inhibiting metabolites such as hydrogen (H2), ammonium/ammonia (NH4+/NH3) or hydrogen sulphide (H2S) and inhibition by other organic and inorganic toxicants. Causes, mechanisms and effects on the biogas microbiome are discussed. The need for a knowledge-based microbiome management to ensure a stable and efficient production of biogas with low susceptibility to disturbances is derived and an outlook on potential future process monitoring and control by means of microbial indicators is provided.

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“…The choice of electron carrier might as well depend on the availability of suitable partner methanogens available in the immediate surroundings (13). Although earlier radiolabeling experiments have shown that the majority of methanogenic propionate degradation in lake sediments proceeds through syntrophic oxidation via succinate (58), one may consider also the alternative fermentation path via transformation of two propionates to three acetates that Smithella propionica catalyzes (36,59,60). This pathway turns out to be an elegant alternative for transferring the "difficult" electrons of propionate oxidation via acetate directly to methane, thus avoiding the thermodynamically difficult oxidation of succinate with protons or CO 2 as the electron acceptor.…”

Section: Pool Sizes Of Fermentation Intermediates and Energy Gains Ofmentioning

confidence: 99%

Formate and Hydrogen as Electron Shuttles in Terminal Fermentations in an Oligotrophic Freshwater Lake Sediment

Montag

Schink

2018

Appl Environ Microbiol

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The energetic situation of terminal fermentations in methanogenesis was analyzed by pool size determinations in sediment cores taken in the oligotrophic Lake Constance, Germany. Distribution profiles of fermentation intermediates and products were measured at three different water depths (2, 10, and 80 m). Methane concentrations were constant below 10 cm of sediment depth. Within the methanogenic zone, concentrations of formate, acetate, propionate, and butyrate varied between 1 and 40 μM, and hydrogen was between 0.5 and 5 Pa. From the distribution profiles of the fermentation intermediates, Gibbs free energy changes for their interconversion were calculated. Pool sizes of formate and hydrogen were energetically nearly equivalent, with -5 ± 5 kJ per mol difference of free energy change (ΔG) for a hypothetical conversion of formate to hydrogen plus CO The ΔG values for conversion of fatty acids to methanogenic substrates and their further conversion to methane and CO were calculated with hydrogen and with formate as intermediates. Syntrophic propionate oxidation reached energetic equilibrium with formate as the sole electron carrier but was sufficiently exergonic if at least some of the electrons were transferred via hydrogen. The energetic consequences of formate versus hydrogen transfer in secondary and methanogenic fermentations indicate that both carrier systems are probably used simultaneously to optimize the energy yields for the partners involved. In the terminal steps of methane formation in freshwater lake sediments, fermenting bacteria cooperate syntrophically with methanogens and homoacetogens at minimum energy increments via interspecies electron transfer. The energy yields of the partner organisms in these cooperations have so far been calculated based mainly on hydrogen partial pressures. In the present study, we also analyzed pools of formate as an alternative electron carrier in sediment cores of an oligotrophic lake. The formate and hydrogen pools appeared to be energetically nearly equivalent and are likely to be used simultaneously for interspecies electron transfer. Calculations of reaction energies of the partners involved suggest that propionate degradation may also proceed through the pathway, which converts propionate via butyrate and acetate to three acetate residues, thus circumventing one energetically difficult fatty acid oxidation step.

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A review on the bioenergetics of anaerobic microbial metabolism close to the thermodynamic limits and its implications for digestion applications

Cited by 156 publications

References 93 publications

Effect of a Profound Feedstock Change on the Structure and Performance of Biogas Microbiomes

Effect of a Profound Feedstock Change on the Structure and Performance of Biogas Microbiomes

Process Disturbances in Agricultural Biogas Production—Causes, Mechanisms and Effects on the Biogas Microbiome: A Review

Formate and Hydrogen as Electron Shuttles in Terminal Fermentations in an Oligotrophic Freshwater Lake Sediment

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