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The ISME Journal Jan 2024The bacterial species "Candidatus Alkanivorans nitratireducens" was recently demonstrated to mediate nitrate-dependent anaerobic oxidation of short-chain gaseous alkanes...
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. Here, we describe anaerobic multispecies cultures of bacteria that couple the oxidation of propane and butane to nitrate reduction and the oxidation of ammonium (anammox). Batch tests with 15N-isotope labelling and multi-omic analyses collectively supported a syntrophic partnership between "Ca. A. nitratireducens" and anammox bacteria, with the former species mediating nitrate-driven oxidation of SCGAs, supplying the latter with nitrite for the oxidation of ammonium. The elimination of nitrite accumulation by the anammox substantially increased SCGA and nitrate consumption rates, whereas it suppressed DNRA. Removing ammonium supply led to its eventual production, the accumulation of nitrite, and the upregulation of DNRA gene expression for the abundant "Ca. A. nitratireducens". Increasing the supply of SCGA had a similar effect in promoting DNRA. Our results suggest that "Ca. A. nitratireducens" switches to DNRA to alleviate oxidative stress caused by nitrite accumulation, giving further insight into adaptability and ecology of this microorganism. Our findings also have important implications for the understanding of the fate of nitrogen and SCGAs in anaerobic environments.
Topics: Oxidation-Reduction; Nitrates; Anaerobiosis; Ammonium Compounds; Alkanes; Microbial Consortia; Nitrites; Bioreactors; Bacteria
PubMed: 38624180
DOI: 10.1093/ismejo/wrae063 -
Scientific Reports Apr 2024The adaptation of biochar in anaerobic digestion (AD) positively influences the conversion of substrate to biomethane and promotes system stability. This study...
The adaptation of biochar in anaerobic digestion (AD) positively influences the conversion of substrate to biomethane and promotes system stability. This study investigated the influence of biochar (BC) doses (0 to 8 g/L) on the Biochemical Methane Potential (BMP) of glucose during a 60-day AD in a mesophilic batch-type reactor. The first 6.5 weeks of the experimentation were dedicated to the microorganism's adaptation to the biochar and degradation of organics from the used inoculum (3 phases of the glucose feeding). The last 2 weeks (4th phase of glucose feeding) represented the assumption, that glucose is the sole carbon source in the system. A machine learning model based on the autoregressive integrated moving average (ARIMA) method was used to model the cumulative BMP. The results showed that the BMP increased with the amount of BC added. The highest BMP was obtained at a dose of 8 g/L, with a maximum cumulative BMP of 390.33 mL CH/g-VS added. Likewise, the system showed stability in the pH (7.17 to 8.17). In contrast, non-amended reactors produced only 135.06 mL CH/g-VS and became acidic at the end of the operation. Reducing the influence of carbon from inoculum, sharpened the positive effect of BC on the kinetics of biomethane production from glucose.
Topics: Carbon; Bioreactors; Anaerobiosis; Charcoal; Methane
PubMed: 38622318
DOI: 10.1038/s41598-024-59313-y -
Environmental Research Jul 2024Mechanistic understanding of acetoclastic methanogenesis is pivotal for optimizing anaerobic digestion for efficient methane production. In this study, two different...
Mechanistic understanding of acetoclastic methanogenesis is pivotal for optimizing anaerobic digestion for efficient methane production. In this study, two different operational modes, continuous flow reactor (CFR) and sequencing batch reactor (SBR), accompanied with solids retention times (SRT) of 10 days (SBR and CFR) and 25 days (SBR and CFR) were implemented to elucidate their impacts on microbial communities and energy metabolism of methanogens in acetate-fed systems. Microbial community analysis revealed that the relative abundance of Methanosarcina (16.0%-46.0%) surpassed Methanothrix (3.7%-22.9%) in each reactor. SBRs had the potential to enrich both Methanothrix and Methanosarcina. Compared to SBRs, CFRs had lower total relative abundance of methanogens. Methanosarcina exhibited a superior enrichment in reactors with 10-day SRT, while Methanothrix preferred to be acclimated in reactors with 25-day SRT. The operational mode and SRT were also observed to affect the distribution of acetate-utilizing bacteria, including Pseudomonas, Desulfocurvus, Mesotoga, and Thauera. Regarding enzymes involved in energy metabolism, Ech and Vho/Vht demonstrated higher relative abundances at 10-day SRT compared to 25-day SRT, whereas Fpo and MtrA-H showed higher relative abundances in SBRs than those in CFRs. The relative abundance of genes encoding ATPase harbored by Methanothrix was higher than Methanosarcina at 25-day SRT. Additionally, the relative abundance of V/A-type ATPase (typically for methanogens) was observed higher in SBRs compared to CFRs, while the F-type ATPase (typically for bacteria) exhibited higher relative abundance in CFRs than that in SBRs.
Topics: Bioreactors; Methane; Energy Metabolism; Acetates; Methanosarcina; Anaerobiosis; Acclimatization
PubMed: 38604482
DOI: 10.1016/j.envres.2024.118911 -
Journal of Environmental Management May 2024This study quantifies the financial and environmental impacts of a microalgal bioenergy system that attempts to maximize circular flows by recovering and reusing the...
Economic and environmental performance of microalgal energy products - A case study exploring circular bioeconomy principles applied to recycled anaerobic digester waste flows.
This study quantifies the financial and environmental impacts of a microalgal bioenergy system that attempts to maximize circular flows by recovering and reusing the carbon, nutrients, and water within the system. The system produces microalgal biomass using liquid digestate of an anaerobic digester that processes 45 metric tons of food waste and generates 28.6 m of permeate daily in California, and three energy production scenarios from the biomass are considered: producing biodiesel, electricity, and both. In all scenarios, the resulting energy products delivered only modest reductions in environmental impacts as measured by carbon dioxide equivalent emissions. The carbon intensities (CIs) of biodiesel from this study were 91.0 gCOe/MJ and 93.3 gCOe/MJ, which were lower than 94.71 gCOe/MJ of conventional petroleum diesel, and the CI of electricity from this study was 70.6 gCOe/MJ, lower than the average electricity grid CI in California (82.92 gCOe/MJ). The economic analysis results show that generating electricity alone can be profitable, while biodiesel produced via this system is not cost competitive with conventional diesel due to high capital expenses. Thus, generating electricity in lieu of biodiesel appears to be a better option to maximize the use of waste flows and supply lower-carbon energy.
Topics: Microalgae; Biofuels; Anaerobiosis; Biomass; Recycling; California; Electricity; Carbon Dioxide
PubMed: 38599084
DOI: 10.1016/j.jenvman.2024.120802 -
Pharmacological Research May 2024Defining the ability of prebiotic dietary carbohydrates to influence the composition and metabolism of the gut microbiota is central to defining their health impact in...
BACKGROUND
Defining the ability of prebiotic dietary carbohydrates to influence the composition and metabolism of the gut microbiota is central to defining their health impact in diverse individuals. Many clinical trials are using indirect methods. This study aimed to validate collection and fermentation methods enabling their use in the context of clinical studies.
METHODS AND RESULTS
Parameters tested included stool sample acquisition, storage, and growth conditions. Stool from 3 infants and 3 adults was collected and stored under varying conditions. Samples were cultured anaerobically for two days in the presence of prebiotics, whereupon optical density and pH were measured across time. Whole genome shotgun sequencing and NMR metabolomics were performed. Neither the type of collection vial (standard vial and two different BD anaerobic collection vials) nor cryopreservation (-80 °C or 4 °C) significantly influenced either microbial composition at 16 h of anaerobic culture or the principal components of the metabolome at 8 or 16 h. Metagenomic differences were driven primarily by subject, while metabolomic differences were driven by fermentation sugar (2'-fucosyllactose or dextrose).
CONCLUSIONS
These data identified a feasible and valid approach for prebiotic fermentation analysis of individual samples in large clinical studies: collection of stool microbiota using standard vials; cryopreservation prior to testing; and collecting fermentation read-out at 8 and 16 hr. Thus, fermentation analysis can be a valid technique for testing the effects of prebiotics on human fecal microbiota.
Topics: Humans; Prebiotics; Fermentation; Gastrointestinal Microbiome; Feces; Infant; Adult; Anaerobiosis; Male; Female; Specimen Handling; Metabolomics
PubMed: 38583688
DOI: 10.1016/j.phrs.2024.107169 -
Bioresource Technology May 2024Hydrothermal liquefaction (HTL) aqueous phases derived from mixed sludge and digested sludge of two wastewater treatment plants (WWTP) were characterized considering...
Hydrothermal liquefaction (HTL) aqueous phases derived from mixed sludge and digested sludge of two wastewater treatment plants (WWTP) were characterized considering variations in primary-secondary sludge ratios, an aspect previously overlooked in the literature. Mixed sludge was obtained by mixing primary and secondary sludge to simulate high primary sludge, average, and high secondary sludge cases. Aerobic and mesophilic/thermophilic anaerobic biodegradability tests were conducted. Higher chemical oxygen demand, total ammonium-N, orthophosphate-P, fatty acids, and N-heterocycles in HTL aqueous samples were detected as the secondary sludge ratio increased in mixed sludge. A similar trend was observed in the biodegradability tests. Characteristics of HTL aqueous derived from mixed sludge of WWTP 1 showed much higher variation, whereas WWTP 2 mixed sludge was not affected significantly by primary-secondary sludge ratios. Finally, the biodegradability levels of HTL aqueous samples were determined to be 69-78 % under aerobic, 58-70 % under mesophilic anaerobic, and 42-56 % under thermophilic anaerobic conditions.
Topics: Sewage; Biodegradation, Environmental; Biological Oxygen Demand Analysis; Water; Temperature; Anaerobiosis; Waste Disposal, Fluid; Wastewater; Cities
PubMed: 38583678
DOI: 10.1016/j.biortech.2024.130671 -
Bioresource Technology May 2024Tetracycline exerts an inhibitory effect on anaerobic digestion, inducing stressed microbial activities and even system failure. Continuous-flow reactors (CFRs) and...
Tetracycline exerts an inhibitory effect on anaerobic digestion, inducing stressed microbial activities and even system failure. Continuous-flow reactors (CFRs) and sequencing batch reactors (SBRs) were employed along with the dosage of powdered activated carbon (PAC) to enhance tetracycline removal during anaerobic digestion of complex organic compounds. PAC increased the maximum methane production rate by 15.6% (CFRs) and 13.8% (SBRs), and tetracycline biodegradation by 24.4% (CFRs) and 19.2% (SBRs). CFRs showed higher tetracycline removal and methane production rates than SBRs. Geobacter was enriched in CFRs, where Methanothrix was enriched with the addition of PAC. Desulfomicrobium harbored abundant propionate degradation-related genes, significantly correlating with tetracycline removal. The genes encoding carbon dioxide reduction in Methanothrix along with the detection of Geobacter might indicate direct interspecies electron transfer for methanogenesis in CFRs and PAC-added reactors. The study offers new insights into anaerobic digestion under tetracycline-stressed conditions and strategies for optimizing tetracycline removal.
Topics: Tetracycline; Anaerobiosis; Bioreactors; Biodegradation, Environmental; Charcoal; Methane; Powders; Organic Chemicals
PubMed: 38583675
DOI: 10.1016/j.biortech.2024.130672 -
Frontiers in Cellular and Infection... 2024Despite extensive knowledge of antibiotic-targeted bacterial cell death, deeper understanding of antibiotic tolerance mechanisms is necessary to combat multi-drug...
Despite extensive knowledge of antibiotic-targeted bacterial cell death, deeper understanding of antibiotic tolerance mechanisms is necessary to combat multi-drug resistance in the global healthcare settings. Regulatory RNAs in bacteria control important cellular processes such as cell division, cellular respiration, metabolism, and virulence. Here, we investigated how exposing to the moderately effective first-generation antibiotic cephalothin alters transcriptional and post-transcriptional dynamics. Bacteria switched from active aerobic respiration to anaerobic adaptation via an FnrS and Tp2 small RNA-mediated post-transcriptional regulatory circuit. From the early hours of antibiotic exposure, FnrS was involved in regulating reactive oxygen species levels, and delayed oxygen consumption in bacteria. We demonstrated that bacteria strive to maintain cellular homeostasis via sRNA-mediated sudden respiratory changes upon sublethal antibiotic exposure.
Topics: RNA; Anti-Bacterial Agents; Anaerobiosis; Cell Respiration; Bacteria; Respiration; Gene Expression Regulation, Bacterial
PubMed: 38577619
DOI: 10.3389/fcimb.2024.1287557 -
Microbial Cell Factories Apr 2024Poultry feather waste has a potential for bioenergy production because of its high protein content. This research explored the use of chicken feather hydrolysate for...
BACKGROUND
Poultry feather waste has a potential for bioenergy production because of its high protein content. This research explored the use of chicken feather hydrolysate for methane and hydrogen production via anaerobic digestion and bioelectrochemical systems, respectively. Solid state fermentation of chicken waste was conducted using a recombinant strain of Bacillus subtilis DB100 (p5.2).
RESULTS
In the anaerobic digestion, feather hydrolysate produced maximally 0.67 Nm CH/kg feathers and 0.85 mmol H/day.L concomitant to COD removal of 86% and 93%, respectively. The bioelectrochemical systems used were microbial fuel and electrolysis cells. In the first using a microbial fuel cell, feather hydrolysate produced electricity with a maximum cell potential of 375 mV and a current of 0.52 mA. In the microbial electrolysis cell, the hydrolysate enhanced the hydrogen production rate to 7.5 mmol/day.L, with a current density of 11.5 A/m and a power density of 9.26 W/m.
CONCLUSIONS
The data indicated that the sustainable utilization of keratin hydrolysate to produce electricity and biohydrogen via bioelectrical chemical systems is feasible. Keratin hydrolysate can produce electricity and biofuels through an integrated aerobic-anaerobic fermentation system.
Topics: Animals; Anaerobiosis; Chickens; Feathers; Hydrogen; Keratins; Methane; Biofuels; Bioreactors
PubMed: 38575972
DOI: 10.1186/s12934-024-02374-5 -
The Science of the Total Environment Jun 2024In this research, we developed a biochar-based fertilizer using biogas slurry and biochar derived from lignocellulosic agro-residues. Biogas slurry was obtained through...
In this research, we developed a biochar-based fertilizer using biogas slurry and biochar derived from lignocellulosic agro-residues. Biogas slurry was obtained through the anaerobic digestion of the organic fraction of municipal solid waste (fresh vegetable biomass and/or prepared food), while biochars were derived from residues from quinoa, maize, rice, and sugarcane. The biochar-based fertilizers were prepared using an impregnation process, where the biogas slurry was mixed with each of the raw biochars. Subsequently, we characterized the N, P and K concentrations of the obtained biochar-based fertilizers. Additionally, we analyzed their surface properties using SEM/EDS and FTIR and conducted a slow-release test on these biochar-based fertilizers to assess their capability to gradually release nutrients. Lastly, a bioassay using cucumber plants was conducted to determine the N, P, and K bioavailability. Our findings revealed a significant correlation (r > 0.67) between the atomic O/C ratio, H/C ratio, cation exchange capacity, surface area, and the base cations concentration with N, P, and/or K adsorption on biochar. These properties, in turn, were linked to the capability of the biochar-based fertilizer to release nutrients in a controlled manner. The biochar-based fertilizer derived from corn residues showed <15 % release of N, P and K at 24 h. Utilization of these biochar-based fertilizers had a positive impact on the mineral nutrition of cucumber plants, resulting in an average increase of 61 % in N, 32 % in P, and 19 % in K concentrations. Our results underscore the potential of biochar-based fertilizers in controlled nutrient release and enhanced plant nutrition. Integration of biochar and biogas slurry offers a promising and sustainable approach for NPK recovery and fertilizer production in agriculture. This study presents an innovative and sustainable approach combining the use of biochar for NPK recovery from biogas slurry and its use as a biochar-based fertilizer in agriculture.
Topics: Fertilizers; Charcoal; Anaerobiosis; Agriculture; Nitrogen; Potassium; Phosphorus; Biofuels
PubMed: 38575013
DOI: 10.1016/j.scitotenv.2024.171982