Kinetics and Stoichiometry of an Efficient Methanotroph Methylosarcina sp. LC-4 Isolated from a Municipal Solid Waste Dumpsite
01 May 2021-Journal of Environmental Engineering (American Society of Civil Engineers)-Vol. 147, Iss: 5, pp 04021011
TL;DR: In recent times methanotrophs have gained immense interest due to their ability to sequester and utilize methane, which is an inexpensive carbon source as well as a very potent greenhouse gas.
Abstract: In recent times methanotrophs have gained immense interest due to their ability to sequester and utilize methane, which is an inexpensive carbon source as well as a very potent greenhouse g...
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TL;DR: In this paper , an efficient methanotroph, Methylosarcina sp. LC-4, was studied as a prospective organism for biodiesel production using methane, and the methane uptake rate by the organism was enhanced 1.6 times and 2.35 times by supplementing it with micronutrients such as copper and tungstate, respectively.
Abstract: The conversion of methane into liquid biofuels using methane-consuming bacteria, known as methanotrophs, contributes to sustainable development, as it mitigates the problem of climate change caused by greenhouse gases and aids in producing cleaner and renewable energy. In the present research, an efficient methanotroph, Methylosarcina sp. LC-4, was studied as a prospective organism for biodiesel production using methane. The methane uptake rate by the organism was enhanced 1.6 times and 2.35 times by supplementing LC-4 with micronutrients, such as copper and tungstate, respectively. This unique ability of the isolated organism enables the deployment of methanotrophs-based processes in various industrial applications. A Plackett–Burman statistical (PBD) design was used to quantify the role of the micronutrients and other media components present in the nitrate minimal salt media (NMS) in biomass and fatty acid methyl esters (FAME) yields. Nitrate, phosphate, and tungstate had a positive effect, whereas copper, magnesium, and salinity had a negative effect. The modified NMS media, formulated according to the results from the PBD analysis, increased the FAME yield (mg/L) by 85.7%, with the FAME content of 13 ± 1% (w/w) among the highest reported in methanotrophs. The obtained FAME consisted majorly (~90%) of C14–C18 saturated and monounsaturated fatty acids, making it suitable for use as biodiesel.
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TL;DR: In this paper , the authors present the current state of research in the last five years on contaminants in soils, especially in leachates from solid waste landfills, with emphasis on biological remediation.
Abstract: This systematic review presents the current state of research in the last five years on contaminants in soils, especially in leachates from solid waste landfills, with emphasis on biological remediation. In this work, the pollutants that can be treated by microorganisms and the results obtained worldwide were studied. All the data obtained were compiled, integrated, and analyzed by soil type, pollutant type, bacterial type, and the countries where these studies were carried out. This review provides reliable data on the contamination of soils worldwide, especially soils contaminated by leachate from municipal landfills. The extent of contamination, treatment objectives, site characteristics, cost, type of microorganisms to be used, and time must be considered when selecting a viable remediation strategy. The results of this study can help develop innovative and applicable methods for evaluating the overall contamination of soil with different contaminants and soil types. These findings can help develop innovative, applicable, and economically feasible methods for the sustainable management of contaminated soils, whether from landfill leachate or other soil types, to reduce or eliminate risk to the environment and human health, and to achieve greater greenery and functionality on the planet.
TL;DR: In this article , a sequential electrochemical oxidation (EO) and algal bubble column photobioreactor (BPBR) system was proposed to treat distillery wastewater (DWW), and the optimal treatment conditions for the growth of A. quadricellulare were 27 A for 26 h and a post-treatment dilution of 8.7%.
Abstract: A sequential electrochemical oxidation (EO) and algal bubble column photobioreactor (BPBR) system was proposed to treat distillery wastewater (DWW). EO was carried out in a 2 L reactor with Ti-RuO2 anodes. Electrochemically oxidised DWW (EO-DWW) was then supplied to the microalgae Asterarcys quadricellulare. The EO operating current, treatment time and post-treatment dilution were optimised with a central composite design (CCD) with algal specific growth rate, lipid accumulation and photosynthetic quantum yield (Fv/Fm) as dependent variables. The optimal treatment conditions for the growth of A. quadricellulare were 27 A for 26 h and a post-treatment dilution of 8. Under optimal conditions, A. quadricellulare grew at a specific growth rate of 1.06 d-1 with a lipid accumulation of 12.7% and an Fv/Fm of 0.7. The optimal conditions were validated, and a 1.6 L bubble column photobioreactor was designed to treat the EO-DWW sequentially. The sequential EO-BPBR system removed 92% COD, 76% TOC and 82% TN from DWW. The algal biomass productivity was 0.96 g/L/d with a carbon sequestration of 550-700 mg/L/d and an aqueous carbon capture of 240-280 mg C/L/d. Additionally, the flue gas evolved from the EO reactor was analysed and contained 68% H2, 18% O2 and 12.5% CO2. The H2 in the flue gas can compensate for 26.5% of the energy spent for the EO process. The algal biomass produced in the sequential process can compensate for 6% of the total energy consumed for EO. Therefore, 32% of the energy spent on EO can be reclaimed by sequential EO-BPBR treatment.
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TL;DR: The concept of microbially mediated methane oxidation in landfill covers by using methanotrophic microorganisms has been widely adopted as a method to counter the rise in methane emissions as discussed by the authors.
Abstract: Mitigation of landfill gases has gained the utmost importance in recent years due to the increase in methane (CH4) emissions from landfills worldwide. This, in turn, can contribute to global warming and climatic changes. The concept of microbially mediated methane oxidation in landfill covers by using methanotrophic microorganisms has been widely adopted as a method to counter the rise in methane emissions. Traditionally, landfill soil covers were used to achieve methane oxidation, thereby reducing methane emissions. Meanwhile, the continual rise of CH4 emissions from landfills and the significant need to and importance of developing a better technology has led researchers to explore different methods to enhance microbial methane oxidation by using organic rich materials such as compost in landfill covers. The development and field application of such bio-based systems, explored by various researches worldwide, eventually led to more widely accepted and better performing cover systems capable of reducing CH4 emissions from landfills. However, the long-term performance of bio-based cover systems were found to be negatively affected by factors such as the material’s ability to self-degrade, causing CH4 to be generated rather than oxidized as well as the greater potential for forming pore-clogging exopolymeric substances. In order to design an effective cover system for landfills, it is essential to have a thorough understanding of the concepts incorporated into methodologies currently in favor along with their pros and cons. This review summarizes previous laboratory and field-scale studies conducted on various soil and bio-based cover systems, along with the modeling mechanisms adopted for quantifying CH4 oxidation rates. Finally, several issues and challenges in developing effective and economical soil and bio-based cover systems are presented.
111 citations
TL;DR: In this study, modeling is used to describe how oxygen and nitrogen source affect the stoichiometry and kinetics of growth and PHB production in the Type II methanotrophs Methylosinus trichosporium OB3b and Methylocystis parvus OBBP.
99 citations
TL;DR: 16S rDNA phylogenetic analysis showed that these are type I methanotrophs (family: Methylococcaceae) most closely related to the Methylobacter/Methylomicrobium clade, although they form a monophyletic grouping supported by moderately high bootstrap values.
Abstract: Two novel species of obligate methane-oxidizing bacteria, isolated from landfill soil, were characterized. Both strains were unusual in that some members of the population grew in irregularly shaped, refractile cell packets that resembled sarcina-like clusters. Electron microscopy revealed that the cell packets were covered with a slime layer and the cells contained many large granular inclusion bodies. The individual cells of each strain were sometimes motile and had differing morphologies. Isolate AML-C10T was always coccoidal in shape, and the cells were covered with extracellular fibrils. Isolate AML-D4T was pleomorphic, changing from rod to coccal form, sometimes exhibiting an unusual fusiform morphology. AML-D4T lacked the extensive fibrillar matrix observed with AML-C10T. Both strains utilized only methane and methanol as carbon sources. In stationary phase, the cells of each strain swelled in size and formed cysts. Aside from morphological differences, strains could also be distinguished from each other by cellular protein patterns, as well as by temperature and pH tolerances. 16S rDNA phylogenetic analysis showed that these are type I methanotrophs (family: Methylococcaceae) most closely related to the Methylobacter/Methylomicrobium clade, although they form a monophyletic grouping supported by moderately high bootstrap values. By 16S rDNA database searches, the most similar species to both isolates were Methylobacter spp. However, partial particulate methane monooxygenase sequence analysis suggested that these bacteria might be more closely related to Methylomicrobium than Methylobacter. Furthermore, cellular fatty acid profiles of the strains more closely resemble those of Methylomicrobium, although the absence of significant levels of 16:1omega5c argues for the uniqueness of these two strains. On the basis of the results described here, it is proposed that a new genus should be created, Methylosarcina gen. nov., harbouring two species, Methylosarcina fibrata sp. nov. (type species) and Methylosarcina quisquiliarum sp. nov. The type strains are AML-C10T (= ATCC 700909T = DSM 13736T) and AML-D4T (= ATCC 700908T = DSM 13737T), respectively.
93 citations
TL;DR: The results presented here represent the most comprehensive published bioreactor datasets for a gamma-proteobacterial methanotroph and show that metabolism by M. buryatense 5GB1 differs significantly for each of the four conditions tested.
Abstract: Methane is a feedstock of interest for the future, both from natural gas and from renewable biogas sources. Methanotrophic bacteria have the potential to enable commercial methane bioconversion to value-added products such as fuels and chemicals. A strain of interest for such applications is Methylomicrobium buryatense 5GB1, due to its robust growth characteristics. However, to take advantage of the potential of this methanotroph, it is important to generate comprehensive bioreactor-based datasets for different growth conditions to compare bioprocess parameters. Datasets of growth parameters, gas utilization rates, and products (total biomass, extracted fatty acids, glycogen, excreted acids) were obtained for cultures of M. buryatense 5GB1 grown in continuous culture under methane limitation and O2 limitation conditions. Additionally, experiments were performed involving unrestricted batch growth conditions with both methane and methanol as substrate. All four growth conditions show significant differences. The most notable changes are the high glycogen content and high formate excretion for cells grown on methanol (batch), and high O2:CH4 utilization ratio for cells grown under methane limitation. The results presented here represent the most comprehensive published bioreactor datasets for a gamma-proteobacterial methanotroph. This information shows that metabolism by M. buryatense 5GB1 differs significantly for each of the four conditions tested. O2 limitation resulted in the lowest relative O2 demand and fed-batch growth on methane the highest. Future studies are needed to understand the metabolic basis of these differences. However, these results suggest that both batch and continuous culture conditions have specific advantages, depending on the product of interest.
89 citations
TL;DR: The kinetics of methane uptake by Methylococcus capsulatus (Bath) and its inhibition by ammonia were studied by stopped-flow membrane-inlet mass spectrometry to agree with the assumption that ammonia is a week alternative substrate for particulate methane monooxygenase.
Abstract: The kinetics of methane uptake by Methylococcus capsulatus (Bath) and its inhibition by ammonia were studied by stopped-flow membrane-inlet mass spectrometry. Measurements were done on suspensions of cells grown in high- and low-copper media. With both types of cells the kinetics of methane uptake are hyperbolic when oxygen is in excess. The apparent K
m and K
max for methane uptake are both higher in low-copper cells than in high-copper cells. Ammonia is a simple competitive inhibitor of methane uptake in high-copper cells when the oxygen concentration is above a few μM. The findings agree with the assumption that ammonia is a week alternative substrate for particulate methane monooxygenase. In low-copper cells the effect of ammonia is complicated and cannot be explained in terms of current assumptions on the mechanism of soluble methane monooxygenase. Our data indicate that ammonia inhibition is likely to be a more serious problem in connection with cultivation in low-copper medium than in high-copper medium.
88 citations