Microbial oxidation of short-chain gaseous alkanes.

Short-chain gaseous alkanes (SCGAs), including ethane, propane and butane, are major components of natural gas and their atmospheric emissions impact global air quality and tropospheric chemistry. Many microbial taxa can degrade SCGAs aerobically and anaerobically to CO, acting as the major biological sink of these compounds and reducing their negative impacts on climate. Environmental metagenomics and cultivation efforts have expanded our understanding of SCGA-oxidizing microorganisms.

Sulfate-reducing capability of nitrate-dependent anaerobic gaseous alkanes degrader.

Microbial oxidation of short-chain gaseous alkanes (SCGAs, including ethane, propane and butane) are important sinks to mitigate the emission of SCGAs to the atmosphere. 'Candidatus Alkanivorans nitratireducens' has been discovered to be capable of utilizing nitrate as an electron acceptor to anaerobically oxidize these SCGAs. However, little is known about its metabolic diversity in sulfate reduction, despite sulfate being widely present in both marine and freshwater ecosystems.

Robust biogas upgrading process via homoacetogens against ammonia and sulfide toxicities.

Using hydrogen derived from surplus green energy (e.g., solar and wind) to convert carbon dioxide to acetate via homoacetogens represents a promising technology for simultaneous biogas upgrading and biochemical production.

Mildly acidic pH boosts up CO conversion to isobutyrate in H driven gas fermentation system.

As a greenhouse gas, massive carbon dioxide (CO) has been generated due to organic matter degradation in wastewater treatment processes. Microbial gas fermentation offers a promising approach to capture CO and generate various valuable chemicals. However, limited studies have achieved branched or medium-chain fatty acids production via gas fermentation.

Simultaneous Biogas Upgrading and Valuable Chemical Production Using Homoacetogens in a Membrane Biofilm Reactor.

Biogas produced from anaerobic digestion usually contains impurities, particularly with a high content of CO (15-60%), thus decreasing its caloric value and limiting its application as an energy source. H-driven biogas upgrading using homoacetogens is a promising approach for upgrading biogas to biomethane and converting CO to acetate simultaneously. Herein, we developed a novel membrane biofilm reactor (MBfR) with H and biogas separately supplied via bubbleless hollow fiber membranes.

Coupling Nitrate-Dependent Anaerobic Ethane Degradation with Anaerobic Ammonium Oxidation.

The microbial oxidation of short-chain gaseous alkanes (SCGAs, consisting of ethane, propane, and butane) serves as an efficient sink to mitigate these gases' emission to the atmosphere, thus reducing their negative impacts on air quality and climate. " Alkanivorans nitratireducens" are recently found to mediate nitrate-dependent anaerobic ethane oxidation (n-DAEO). In natural ecosystems, anaerobic ammonium-oxidizing (anammox) bacteria may consume nitrite generated from nitrate reduction by " A.

Anaerobic oxidation of ammonium and short-chain gaseous alkanes coupled to nitrate reduction by a bacterial consortium.

The bacterial species "Candidatus Alkanivorans nitratireducens" was recently demonstrated to mediate nitrate-dependent anaerobic oxidation of short-chain gaseous alkanes (SCGAs). In previous bioreactor enrichment studies, the species appeared to reduce nitrate in two phases, switching from denitrification to dissimilatory nitrate reduction to ammonium (DNRA) in response to nitrite accumulation. The regulation of this switch or the nature of potential syntrophic partnerships with other microorganisms remains unclear.

Bioreduction of chromate in a syngas-based membrane biofilm reactor.

This study leveraged synthesis gas (syngas), a renewable resource attainable through the gasification of biowaste, to achieve efficient chromate removal from water. To enhance syngas transfer efficiency, a membrane biofilm reactor (MBfR) was employed. Long-term reactor operation showed a stable and high-level chromate removal efficiency > 95%, yielding harmless Cr(III) precipitates, as visualised by scanning electron microscopy and energy dispersive X-ray analysis.

Revisiting methane-dependent denitrification.

Methane-dependent denitrification links the global nitrogen and methane cycles. Since its initial discovery in 2006, this process has been understood to involve a division of labor between an archaeal group and a bacterial group, which sequentially perform nitrate and nitrite reduction, respectively. Yao et al.

Nitrate-driven anaerobic oxidation of ethane and butane by bacteria.

The short-chain gaseous alkanes (ethane, propane, and butane; SCGAs) are important components of natural gas, yet their fate in environmental systems is poorly understood. Microbially mediated anaerobic oxidation of SCGAs coupled to nitrate reduction has been demonstrated for propane, but is yet to be shown for ethane or butane-despite being energetically feasible. Here we report two independent bacterial enrichments performing anaerobic ethane and butane oxidation, respectively, coupled to nitrate reduction to dinitrogen gas and ammonium.

Methane Oxidation Coupled to Selenate Reduction in a Membrane Bioreactor under Oxygen-Limiting Conditions.

Microbial methane oxidation coupled to a selenate reduction process has been proposed as a promising solution to treat contaminated water, yet the underlying microbial mechanisms are still unclear. In this study, a novel methane-based membrane bioreactor system integrating hollow fiber membranes for efficient gas delivery and ultrafiltration membranes for biomass retention was established to successfully enrich abundant suspended cultures able to perform methane-dependent selenate reduction under oxygen-limiting conditions. The microbial metabolic mechanisms were then systematically investigated through a combination of short-term batch tests, DNA-based stable isotope probing (SIP) microcosm incubation, and high-throughput sequencing analyses of 16S rRNA gene and functional genes ( and ).

Microbial nitrate reduction in propane- or butane-based membrane biofilm reactors under oxygen-limiting conditions.

Nitrate contamination has been commonly detected in water environments and poses serious hazards to human health. Previously methane was proposed as a promising electron donor to remove nitrate from contaminated water. Compared with pure methane, natural gas, which not only contains methane but also other short chain gaseous alkanes (SCGAs), is less expensive and more widely available, representing a more attractive electron source for removing oxidized contaminants.

Anaerobic oxidation of propane coupled to nitrate reduction by a lineage within the class Symbiobacteriia.

Anaerobic microorganisms are thought to play a critical role in regulating the flux of short-chain gaseous alkanes (SCGAs; including ethane, propane and butane) from terrestrial and aquatic ecosystems to the atmosphere. Sulfate has been confirmed to act as electron acceptor supporting microbial anaerobic oxidation of SCGAs, yet several other energetically more favourable acceptors co-exist with these gases in anaerobic environments. Here, we show that a bioreactor seeded with biomass from a wastewater treatment facility can perform anaerobic propane oxidation coupled to nitrate reduction to dinitrogen gas and ammonium.

Copper stimulation on methane-supported perchlorate reduction in a membrane biofilm reactor.

The present study demonstrated that the perchlorate reduction rate in a methane-based membrane biofilm reactor was significantly enhanced from 14.4 to 25.6 mg-Cl/L/d by increasing copper concentration in the feeding medium from 1 to 10 μM, indicating a stimulatory effect of copper on the methane-supported perchlorate reduction process.

Cross-feeding interactions in short chain gaseous alkane-driven perchlorate and selenate reduction.

Short chain gaseous alkanes (SCGAs) mainly consist of methane (CH), ethane (CH), propane (CH) and butane (CH). The first three SCGAs have been shown to remove perchlorate (ClO) and selenate (SeO), yet it is unknown whether CH is available to reduce these contaminants. This study demonstrated that CH fed biofilms were capable of reducing ClO and SeO to chloride (Cl) and elemental selenium (Se), respectively, by employing two independent membrane biofilms reactors (MBfRs).

Roles of Oxygen in Methane-dependent Selenate Reduction in a Membrane Biofilm Reactor: Stimulation or Suppression.

Although methane (CH) has been proven to be able to serve as an electron donor for bio-reducing various oxidized contaminants (e.g., selenate (SeO)), little is known regarding the roles of oxygen in methane-based reduction processes.

Making good use of methane to remove oxidized contaminants from wastewater.

Being an energetic fuel, methane is able to support microbial growth and drive the reduction of various electron acceptors. These acceptors include a broad range of oxidized contaminants (e.g.

Prevalence and Risk Factors Associated With Self-reported Psychological Distress Among Children and Adolescents During the COVID-19 Pandemic in China.

Importance: Schools have been suspended nationwide in 188 countries, and classes have shifted to home-based distance learning models to control the spread of the coronavirus disease 2019 (COVID-19) pandemic. Additional information is needed to determine mental health status among school-aged children and adolescents during this public health crisis and the risk factors associated with psychological distress during the pandemic.

Objective: To assess self-reported psychological distress among school-aged children and adolescents associated with the COVID-19 pandemic.

Microbial Perchlorate Reduction Driven by Ethane and Propane.

Previous studies demonstrated that methane can be used as an electron donor to microbially remove various oxidized contaminants in groundwater. Natural gas, which is more widely available and less expensive than purified methane, is potentially an alternative source of methane. However, natural gas commonly contains a considerable amount of ethane (CH) and propane (CH), in addition to methane.

Sulfur-based Mixotrophic Vanadium (V) Bio-reduction towards Lower Organic Requirement and Sulfate Accumulation.

Although remediation of toxic vanadium (V) [V(V)] pollution can be achieved through either heterotrophic or sulfur-based autotrophic microbial reduction, these processes would require a large amount of organic carbons or generate excessive sulfate. This study reported that by using mixotrophic V(V) bio-reduction with acetate and elemental sulfur [S(0)] as joint electron donors, V(V) removal performance was enhanced due to cooccurrence of heterotrophic and autotrophic activities. Deposited vanadium (IV) was identified as the main reduction product by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy.

Transcriptomics Uncovers the Response of Anammox Bacteria to Dissolved Oxygen Inhibition and the Subsequent Recovery Mechanism.

Understanding the recovery of anaerobic ammonium-oxidizing (anammox) bacteria after inhibition by dissolved oxygen (DO) is critical for the successful applications of anammox-based processes. Therefore, the effects of oxygen exposure (2 mg L DO for 90 min) and subsequent recovery treatments [N purging or nano zero-valent iron (nZVI) addition] on the activity and gene expression in a enrichment culture were examined. Combining the self-organizing map clustering and enrichment analysis, we proposed the oxidative stress response of anammox bacteria based on the existing concepts of oxidative stress in microbes: the DO exposure triggered a stringent response in , which downregulated the transcription levels of genes involved in the central metabolism and diverted energy to a flagellar assembly and metal transport modules; these changes possibly promoted survival during the inhibition of anammox activity.

Microbial selenate reduction in membrane biofilm reactors using ethane and propane as electron donors.

Selenate (Se(VI)) contamination in groundwater is one of major concerns for human health, in particular in shale gas extraction sites. Microbial selenate reduction coupled to methane (CH) oxidation has been demonstrated very recently. Little is known whether ethane (CH) and butane (CH) are able to drive selenate reduction, although they are also important components in shale gas.

Microbial chromate reduction coupled with anaerobic oxidation of methane in a membrane biofilm reactor.

It has been reported that microbial reduction of sulfate, nitrite/nitrate and iron/manganese could be coupled with anaerobic oxidation of methane (AOM), which plays a significant role in controlling methane emission from anoxic niches. However, little is known about microbial chromate (Cr(VI)) reduction coupling with AOM. In this study, a microbial consortium was enriched via switching nitrate dosing to chromate feeding as the sole electron acceptor under anaerobic condition in a membrane biofilm reactor (MBfR), in which methane was continuously provided as the electron donor through bubble-less hollow fiber membranes.

Perchlorate bio-reduction in a methane-based membrane biofilm reactor in the presence and absence of oxygen.

Perchlorate has been widely detected in various water environments and could cause serious health problems. Methane has been proposed as a promising electron donor to remove perchlorate from contaminated water, yet it is unclear whether and how microbial methane oxidation couples with perchlorate reduction, in particular under anoxic conditions. Here, the feasibility and performance of perchlorate reduction driven by methane in the presence and absence of oxygen were investigated and compared in a lab-scale methane-based membrane biofilm reactor.