-
Frontiers in Microbiology 2023Production of methane by methanogenic archaea, or methanogens, in the rumen of ruminants is a thermodynamic necessity for microbial conversion of feed to volatile fatty... (Review)
Review
Production of methane by methanogenic archaea, or methanogens, in the rumen of ruminants is a thermodynamic necessity for microbial conversion of feed to volatile fatty acids, which are essential nutrients for the animals. On the other hand, methane is a greenhouse gas and its production causes energy loss for the animal. Accordingly, there are ongoing efforts toward developing effective strategies for mitigating methane emissions from ruminant livestock that require a detailed understanding of the diversity and ecophysiology of rumen methanogens. Rumen methanogens evolved from free-living autotrophic ancestors through genome streamlining involving gene loss and acquisition. The process yielded an oligotrophic lifestyle, and metabolically efficient and ecologically adapted descendants. This specialization poses serious challenges to the efforts of obtaining axenic cultures of rumen methanogens, and consequently, the information on their physiological properties remains in most part inferred from those of their non-rumen representatives. This review presents the current knowledge of rumen methanogens and their metabolic contributions to enteric methane production. It also identifies the respective critical gaps that need to be filled for aiding the efforts to mitigate methane emission from livestock operations and at the same time increasing the productivity in this critical agriculture sector.
PubMed: 38029083
DOI: 10.3389/fmicb.2023.1296008 -
Medical Gas Research 2023Methane has shown protective effects on a variety of diseases. Among these, neurological diseases have attracted much attention. However, there are many different... (Review)
Review
Methane has shown protective effects on a variety of diseases. Among these, neurological diseases have attracted much attention. However, there are many different indicators and application methods of methane in the treatment of neurological diseases. In this review, we summarize the indicators related to the protective effects of methane and evaluate the preparation and administration of methane. Thus, we hope to offer available indicators and effective ways to produce and administer methane in future research.
Topics: Methane; Nervous System Diseases; Humans
PubMed: 37077112
DOI: 10.4103/2045-9912.372663 -
Water Research Jul 2023Chemical dosing is the most used strategy for sulfide and methane abatement in urban sewer systems. Although conventional physicochemical methods, such as sulfide... (Review)
Review
Chemical dosing is the most used strategy for sulfide and methane abatement in urban sewer systems. Although conventional physicochemical methods, such as sulfide oxidation (e.g., oxygen/nitrate), precipitation (e.g., iron salts), and pH elevation (e.g., magnesium hydroxide/sodium hydroxide) have been used since the last century, the high chemical cost, large environmental footprint, and side-effects on downstream treatment processes demand a sustainable and cost-effective alternative to these approaches. In this paper, we aimed to review the currently used chemicals and significant progress made in sustainable sulfide and methane abatement technology, including 1) the use of bio-inhibitors, 2) in situ chemical production, and 3) an effective dosing strategy. To enhance the cost-effectiveness of chemical applications in urban sewer systems, two research directions have emerged: 1) online control and optimization of chemical dosing strategies and 2) integrated use of chemicals in urban sewer and wastewater treatment systems. The integration of these approaches offers considerable system-wide benefits; however, further development and comprehensive studies are required.
Topics: Sewage; Sulfides; Nitrates; Water Purification; Methane
PubMed: 37257296
DOI: 10.1016/j.watres.2023.120108 -
Chemical Reviews Feb 2024Methane is a potent greenhouse gas that contributes significantly to climate change and is primarily regulated in Nature by methanotrophic bacteria, which consume... (Review)
Review
Methane is a potent greenhouse gas that contributes significantly to climate change and is primarily regulated in Nature by methanotrophic bacteria, which consume methane gas as their source of energy and carbon, first by oxidizing it to methanol. The direct oxidation of methane to methanol is a chemically difficult transformation, accomplished in methanotrophs by complex methane monooxygenase (MMO) enzyme systems. These enzymes use iron or copper metallocofactors and have been the subject of detailed investigation. While the structure, function, and active site architecture of the copper-dependent particulate methane monooxygenase (pMMO) have been investigated extensively, its putative quaternary interactions, regulation, requisite cofactors, and mechanism remain enigmatic. The iron-dependent soluble methane monooxygenase (sMMO) has been characterized biochemically, structurally, spectroscopically, and, for the most part, mechanistically. Here, we review the history of MMO research, focusing on recent developments and providing an outlook for future directions of the field. Engineered biological catalysis systems and bioinspired synthetic catalysts may continue to emerge along with a deeper understanding of the molecular mechanisms of biological methane oxidation. Harnessing the power of these enzymes will necessitate combined efforts in biochemistry, structural biology, inorganic chemistry, microbiology, computational biology, and engineering.
Topics: Copper; Methane; Iron; Methanol; Oxygenases; Oxidation-Reduction; Mixed Function Oxygenases
PubMed: 38305159
DOI: 10.1021/acs.chemrev.3c00727 -
Applied Microbiology and Biotechnology Sep 2023Climate change due to the continuous increase in the release of green-house gasses associated with anthropogenic activity has made a significant impact on the... (Review)
Review
Climate change due to the continuous increase in the release of green-house gasses associated with anthropogenic activity has made a significant impact on the sustainability of life on our planet. Methane (CH) is a green-house gas whose concentrations in the atmosphere are on the rise. CH measurement is important for both the environment and the safety at the industrial and household level. Methanotrophs are distinguished for their unique characteristic of using CH as the sole source of carbon and energy, due to the presence of the methane monooxygenases that oxidize CH under ambient temperature conditions. This has attracted interest in the use of methanotrophs in biotechnological applications as well as in the development of biosensing systems for CH quantification and monitoring. Biosensing systems using methanotrophs rely on the use of whole microbial cells that oxidize CH in presence of O, so that the CH concentration is determined in an indirect manner by measuring the decrease of O level in the system. Although several biological properties of methanotrophic microorganisms still need to be characterized, different studies have demonstrated the feasibility of the use of methanotrophs in CH measurement. This review summarizes the contributions in methane biosensing systems and presents a prospective of the valid use of methanotrophs in this field. KEY POINTS: • Methanotroph environmental relevance in methane oxidation • Methanotroph biotechnological application in the field of biosensing • Methane monooxygenase as a feasible biorecognition element in biosensors.
Topics: Methane; Oxidation-Reduction; Gases; Biotechnology; Climate Change; Soil Microbiology
PubMed: 37486352
DOI: 10.1007/s00253-023-12629-7 -
Current Opinion in Biotechnology Dec 2023A wide variety of wasted or underutilized organic feedstocks can be leveraged to build a sustainable bioeconomy, ranging from crop residues to food processor residues... (Review)
Review
A wide variety of wasted or underutilized organic feedstocks can be leveraged to build a sustainable bioeconomy, ranging from crop residues to food processor residues and municipal wastes. Leveraging these feedstocks is both high-risk and high-reward. Converting mixed, variable, and/or highly contaminated feedstocks can pose engineering and economic challenges. However, converting these materials to fuels and chemicals can divert waste from landfills, reduce fugitive methane emissions, and enable more responsible forest management to reduce the frequency and severity of wildfires. Historically, low-value components, including ash and lignin, are poised to become valuable coproducts capable of supplementing cement and valuable chemicals. Here, we evaluate the challenges and opportunities associated with converting a range of feedstocks to renewable fuels and chemicals.
Topics: Methane; Recycling; Waste Management; Renewable Energy
PubMed: 37935087
DOI: 10.1016/j.copbio.2023.103017 -
The ISME Journal Jul 2023Protozoa comprise a major fraction of the microbial biomass in the rumen microbiome, of which the entodiniomorphs (order: Entodiniomorphida) and holotrichs (order:...
Protozoa comprise a major fraction of the microbial biomass in the rumen microbiome, of which the entodiniomorphs (order: Entodiniomorphida) and holotrichs (order: Vestibuliferida) are consistently observed to be dominant across a diverse genetic and geographical range of ruminant hosts. Despite the apparent core role that protozoal species exert, their major biological and metabolic contributions to rumen function remain largely undescribed in vivo. Here, we have leveraged (meta)genome-centric metaproteomes from rumen fluid samples originating from both cattle and goats fed diets with varying inclusion levels of lipids and starch, to detail the specific metabolic niches that protozoa occupy in the context of their microbial co-habitants. Initial proteome estimations via total protein counts and label-free quantification highlight that entodiniomorph species Entodinium and Epidinium as well as the holotrichs Dasytricha and Isotricha comprise an extensive fraction of the total rumen metaproteome. Proteomic detection of protozoal metabolism such as hydrogenases (Dasytricha, Isotricha, Epidinium, Enoploplastron), carbohydrate-active enzymes (Epidinium, Diplodinium, Enoploplastron, Polyplastron), microbial predation (Entodinium) and volatile fatty acid production (Entodinium and Epidinium) was observed at increased levels in high methane-emitting animals. Despite certain protozoal species having well-established reputations for digesting starch, they were unexpectedly less detectable in low methane emitting-animals fed high starch diets, which were instead dominated by propionate/succinate-producing bacterial populations suspected of being resistant to predation irrespective of host. Finally, we reaffirmed our abovementioned observations in geographically independent datasets, thus illuminating the substantial metabolic influence that under-explored eukaryotic populations have in the rumen, with greater implications for both digestion and methane metabolism.
Topics: Animals; Cattle; Rumen; Proteomics; Ciliophora; Ruminants; Starch; Methane
PubMed: 37169869
DOI: 10.1038/s41396-023-01407-y -
Photocatalytic Conversion of Methane: Current State of the Art, Challenges, and Future Perspectives.ACS Environmental Au Sep 2023With 28-34 times the greenhouse effect of CO over a 100-year period, methane is regarded as the second largest contributor to global warming. Reducing methane emissions... (Review)
Review
With 28-34 times the greenhouse effect of CO over a 100-year period, methane is regarded as the second largest contributor to global warming. Reducing methane emissions is a necessary measure to limit global warming to below 1.5 °C. Photocatalytic conversion of methane is a promising approach to alleviate the atmospheric methane concentrations due to its low energy consumption and environmentally friendly characteristics. Meanwhile, this conversion process can produce valuable chemicals and liquid fuels such as CHOH, CHCHOH, CH, and CH, cutting down the dependence of chemical production on crude oil. However, the development of photocatalysts with a high methane conversion efficiency and product selectivity remains challenging. In this review, we overview recent advances in semiconductor-based photocatalysts for methane conversion and present catalyst design strategies, including morphology control, heteroatom doping, facet engineering, and cocatalysts modification. To gain a comprehensive understanding of photocatalytic methane conversion, the conversion pathways and mechanisms in these systems are analyzed in detail. Moreover, the role of electron scavengers in methane conversion performance is briefly discussed. Subsequently, we summarize the anthropogenic methane emission scenarios on earth and discuss the application potential of photocatalytic methane conversion. Finally, challenges and future directions for photocatalytic methane conversion are presented.
PubMed: 37743954
DOI: 10.1021/acsenvironau.3c00002 -
Environmental Microbiology Reports Aug 2023Methanotrophs have been identified and isolated from acidic environments such as wetlands, acidic soils, peat bogs, and groundwater aquifers. Due to their methane (CH )... (Review)
Review
Methanotrophs have been identified and isolated from acidic environments such as wetlands, acidic soils, peat bogs, and groundwater aquifers. Due to their methane (CH ) utilization as a carbon and energy source, acidophilic methanotrophs are important in controlling the release of atmospheric CH , an important greenhouse gas, from acidic wetlands and other environments. Methanotrophs have also played an important role in the biodegradation and bioremediation of a variety of pollutants including chlorinated volatile organic compounds (CVOCs) using CH monooxygenases via a process known as cometabolism. Under neutral pH conditions, anaerobic bioremediation via carbon source addition is a commonly used and highly effective approach to treat CVOCs in groundwater. However, complete dechlorination of CVOCs is typically inhibited at low pH. Acidophilic methanotrophs have recently been observed to degrade a range of CVOCs at pH < 5.5, suggesting that cometabolic treatment may be an option for CVOCs and other contaminants in acidic aquifers. This paper provides an overview of the occurrence, diversity, and physiological activities of methanotrophs in acidic environments and highlights the potential application of these organisms for enhancing contaminant biodegradation and bioremediation.
Topics: Biodegradation, Environmental; Wetlands; Methane; Groundwater
PubMed: 37041665
DOI: 10.1111/1758-2229.13156 -
Microbiome Oct 2023Goat is an important livestock worldwide, which plays an indispensable role in human life by providing meat, milk, fiber, and pelts. Despite recent significant advances...
BACKGROUND
Goat is an important livestock worldwide, which plays an indispensable role in human life by providing meat, milk, fiber, and pelts. Despite recent significant advances in microbiome studies, a comprehensive survey on the goat microbiomes covering gastrointestinal tract (GIT) sites, developmental stages, feeding styles, and geographical factors is still unavailable. Here, we surveyed its multi-kingdom microbial communities using 497 samples from ten sites along the goat GIT.
RESULTS
We reconstructed a goat multi-kingdom microbiome catalog (GMMC) including 4004 bacterial, 71 archaeal, and 7204 viral genomes and annotated over 4,817,256 non-redundant protein-coding genes. We revealed patterns of feeding-driven microbial community dynamics along the goat GIT sites which were likely associated with gastrointestinal food digestion and absorption capabilities and disease risks, and identified an abundance of large intestine-enriched genera involved in plant fiber digestion. We quantified the effects of various factors affecting the distribution and abundance of methane-producing microbes including the GIT site, age, feeding style, and geography, and identified 68 virulent viruses targeting the methane producers via a comprehensive virus-bacterium/archaea interaction network.
CONCLUSIONS
Together, our GMMC catalog provides functional insights of the goat GIT microbiota through microbiome-host interactions and paves the way to microbial interventions for better goat and eco-environmental qualities. Video Abstract.
Topics: Animals; Archaea; Bacteria; Gastrointestinal Tract; Goats; Methane; Microbiota
PubMed: 37779211
DOI: 10.1186/s40168-023-01651-6