Trends in Methane-Based Biotechnology

A special issue of Methane (ISSN 2674-0389).

Deadline for manuscript submissions: 30 April 2024 | Viewed by 6844

Special Issue Editors

Institute of Sustainable Processes, Universidad de Valladolid, Valladolid, Spain
Interests: biorefinery; gas-to-product conversion; mass transfer; methane; polyhydroxyalkanoates; resource utilization
GENIA Bioenergy, Valencia, Spain
Interests: biorefinery; gas fermentation; methane; carbon dioxide; biopolymers; waste valorisation
Department of Industrial Engineering, University of Applied Sciences Technikum Wien, Hoechstaedtplatz 6, 1200 Vienna, Austria
Interests: gas fermentation; single cell protein; biopolymers; polyhydroxybutyrate (PHB); polyhydroxyalkaoates (PHA); climate change mitigation and adaptation

Special Issue Information

Dear Colleagues,

In a global context of increasing climate emergency and energy demand, the use of methane (the second most prevalent anthropogenic greenhouse gas) as a resource can play a crucial role not only in combating global warming but also in the transition towards a climate-neutral society. The development of an integrated biorefinery for the generation of bio-compounds of interest from methane-laden waste emissions has recently emerged as an opportunity to address the mitigation of (uncontrolled) GHG emissions along with the reduction in todays’ global dependence on fossil fuels, or other contemporary challenges such as plastic pollution or food scarcity. In this context, methane-utilizing cell factories are envisioned as a promising platform for the bioconversion of the CH4 fraction into green chemicals such as polyhydroxyalkanoates, single-cell protein, biofuels, or platform chemicals. In the particular case of the biogas industry, this biorefinery concept opens up a new window in terms of economic sustainability and the promotion of biogas industry growth, untapping its enormous potential and environmental benefits.

This Special Issue intends to cover all the relevant aspects and recent achievements in methane recovery, treatment and utilization, the latter with a particular focus on methane bioconversion into high value-added chemicals.

Potential topics may include, but are not limited to, the following:

  • Microbial cycling of methane
  • Advances in pathway/metabolic engineering
  • Methane abatement biotechnologies
  • Methane to (bio)products (bio)catalysis
  • Case studies in methane bioconversion

Dr. Yadira Rodríguez
Dr. Juan Carlos López
Dr. Maximilian Lackner
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Methane is an international peer-reviewed open access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bio-molecules
  • bioconversion
  • gas fermentation
  • greenhouse gases mitigation
  • gas-liquid mass transfer
  • methane biorefinery
  • methanotrophic bacteria

Published Papers (4 papers)

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Research

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19 pages, 3151 KiB  
Article
Genetical and Biochemical Basis of Methane Monooxygenases of Methylosinus trichosporium OB3b in Response to Copper
by Dipayan Samanta, Tanvi Govil, Priya Saxena, Lee Krumholz, Venkataramana Gadhamshetty, Kian Mau Goh and Rajesh K. Sani
Methane 2024, 3(1), 103-121; https://doi.org/10.3390/methane3010007 - 20 Feb 2024
Viewed by 408
Abstract
Over the past decade, copper (Cu) has been recognized as a crucial metal in the differential expression of soluble (sMMO) and particulate (pMMO) forms of methane monooxygenase (MMO) through a mechanism referred to as the “Cu switch”. In this study, we used Methylosinus [...] Read more.
Over the past decade, copper (Cu) has been recognized as a crucial metal in the differential expression of soluble (sMMO) and particulate (pMMO) forms of methane monooxygenase (MMO) through a mechanism referred to as the “Cu switch”. In this study, we used Methylosinus trichosporium OB3b as a model bacterium to investigate the range of Cu concentrations that trigger the expression of sMMO to pMMO and its effect on growth and methane oxidation. The Cu switch was found to be regulated within Cu concentrations from 3 to 5 µM, with a strict increase in the methane consumption rates from 3.09 to 3.85 µM occurring on the 6th day. Our findings indicate that there was a decrease in the fold changes in the expression of methanobactin (Mbn) synthesis gene (mbnA) with a higher Cu concentration, whereas the Ton-B siderophore receptor gene (mbnT) showed upregulation at all Cu concentrations. Furthermore, the upregulation of the di-heme enzyme at concentrations above 5 µM Cu may play a crucial role in the copper switch by increasing oxygen consumption; however, the role has yet not been elucidated. We developed a quantitative assay based on the naphthalene–Molisch principle to distinguish between the sMMO- and pMMO-expressing cells, which coincided with the regulation profile of the sMMO and pMMO genes. At 0 and 3 µM Cu, the naphthol concentration was higher (8.1 and 4.2 µM, respectively) and gradually decreased to 0 µM naphthol when pMMO was expressed and acted as the sole methane oxidizer at concentrations above 5 µM Cu. Using physical protein–protein interaction, we identified seven transporters, three cell wall biosynthesis or degradation proteins, Cu resistance operon proteins, and 18 hypothetical proteins that may be involved in Cu toxicity and homeostasis. These findings shed light on the key regulatory genes of the Cu switch that will have potential implications for bioremediation and biotechnology applications. Full article
(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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11 pages, 4501 KiB  
Article
Exploring the Potential of Methanotrophs for Plant Growth Promotion in Rice Agriculture
by Jyoti A. Mohite, Kumal Khatri, Kajal Pardhi, Shubha S. Manvi, Rutuja Jadhav, Shilpa Rathod and Monali C. Rahalkar
Methane 2023, 2(4), 361-371; https://doi.org/10.3390/methane2040024 - 27 Sep 2023
Viewed by 1522
Abstract
Rice fields are one of the important anthropogenic sources of methane emissions. Methanotrophs dwelling near the rice roots and at the oxic–anoxic interface of paddy fields can oxidize a large fraction of the generated methane and are therefore considered to be important. Nitrogen [...] Read more.
Rice fields are one of the important anthropogenic sources of methane emissions. Methanotrophs dwelling near the rice roots and at the oxic–anoxic interface of paddy fields can oxidize a large fraction of the generated methane and are therefore considered to be important. Nitrogen fixation in rice root-associated methanotrophs is well known. Our aim in this study was to explore the potential of methanotrophs as bio-inoculants for rice and the studies were performed in pot experiments in monsoon. Ten indigenously isolated methanotrophs were used belonging to eight diverse genera of Type Ia, Type Ib, and Type II methanotrophs, including the newly described genera and/or species, Methylocucumis oryzae and Methylolobus aquaticus, as well as Ca. Methylobacter oryzae and Ca. Methylobacter coli. Additionally, two consortia (Methylomonas strains and Methylocystis-Methylosinus strains) were used. Nitrogen fixation pathways or nifH genes were detected in all of the used methanotrophs. Plant growth promotion (PGPR) was seen in terms of increased plant height and grain yield. Nine out of twelve (seven single strains and two consortia) showed positive effects on grain yield (6–38%). The highest increase in grain yield was seen after inoculation with Ca. Methylobacter coli (38%) followed by Methylomonas consortium (35%) and Methylocucumis oryzae (31%). Methylomagnum ishizawai inoculated plants showed the highest plant height. Methylocucumis oryzae inoculated plants showed early flowering, grain formation, and grain maturation (~17–18 days earlier). In all the pot experiments, minimal quantities of nitrogen fertilizer were used with no additional organic fertilizer inputs. The present study demonstrated the possibility of developing methanotrophs as bio-inoculants for rice agriculture, which would promote plant growth under low inputs of nitrogenous fertilizers. Although the effect of methanotrophs on methane mitigation is still under investigation, their application to reduce methane emissions from rice fields could be an added advantage. Full article
(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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Review

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27 pages, 4828 KiB  
Review
Methane Biofiltration Processes: A Summary of Biotic and Abiotic Factors
by Fatemeh Ahmadi, Tatiana Bodraya and Maximilian Lackner
Methane 2024, 3(1), 122-148; https://doi.org/10.3390/methane3010008 - 21 Feb 2024
Viewed by 477
Abstract
The ongoing yearly rise in worldwide methane (CH4) emissions is mostly due to human activities. Nevertheless, since over half of these emissions are scattered and have a concentration of less than 3% (v/v), traditional physical–chemical methods are [...] Read more.
The ongoing yearly rise in worldwide methane (CH4) emissions is mostly due to human activities. Nevertheless, since over half of these emissions are scattered and have a concentration of less than 3% (v/v), traditional physical–chemical methods are not very effective in reducing them. In this context, biotechnologies like biofiltration using methane-consuming bacteria, also known as methanotrophs, offer a cost-efficient and practical approach to addressing diffuse CH4 emissions. The present review describes recent findings in biofiltration processes as one of the earliest biotechnologies for treating polluted air. Specifically, impacts of biotic (such as cooperation between methanotrophs and non-methanotrophic bacteria and fungi) and abiotic factors (such as temperature, salinity, and moisture) that influence CH4 biofiltration were compiled. Understanding the processes of methanogenesis and methanotrophy holds significant importance in the development of innovative agricultural practices and industrial procedures that contribute to a more favourable equilibrium of greenhouse gases. The integration of advanced genetic analyses can enable holistic approaches for unravelling the potential of biological systems for methane mitigation. This study pioneers a holistic approach to unravelling the biopotential of methanotrophs, offering unprecedented avenues for biotechnological applications. Full article
(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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25 pages, 2822 KiB  
Review
Methane Oxidation via Chemical and Biological Methods: Challenges and Solutions
by Dipayan Samanta and Rajesh K. Sani
Methane 2023, 2(3), 279-303; https://doi.org/10.3390/methane2030019 - 19 Jul 2023
Cited by 3 | Viewed by 3673
Abstract
Methane, a potent greenhouse gas, has gained significant attention due to its environmental impact and economic potential. Chemical industries have focused on specialized catalytic systems, like zeolites, to convert methane into methanol. However, inherent limitations in selectivity, irreversibility, and pore blockages result in [...] Read more.
Methane, a potent greenhouse gas, has gained significant attention due to its environmental impact and economic potential. Chemical industries have focused on specialized catalytic systems, like zeolites, to convert methane into methanol. However, inherent limitations in selectivity, irreversibility, and pore blockages result in high costs and energy requirements, thus hindering their commercial viability and profitability. In contrast, biological methane conversion using methanotrophs has emerged as a promising alternative, offering higher conversion rates, self-renewability, improved selectivity, and economically feasible upstream processes. Nevertheless, biological methane oxidation encounters challenges including the difficulty in cultivating methanotrophs and their slow growth rates, which hinder large-scale bioprocessing. Another highlighted limitation is the limited mass transfer of methane into liquid in bioreactors. Practical strategies to enhance methane oxidation in biological systems, including optimizing reactor design to improve mass transfer, altering metal concentrations, genetic engineering of methane monooxygenases, enzyme encapsulation, and utilizing microbial consortia are discussed. By addressing the limitations of chemical approaches and highlighting the potential of biological methods, the review concluded that the utilization of genetically engineered methanotrophic biofilms on beads within a biotrickling reactor, along with enhanced aeration rates, will likely enhance methane oxidation and subsequent methane conversion rates. Full article
(This article belongs to the Special Issue Trends in Methane-Based Biotechnology)
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