Biodegradation Of Oil Research Articles

Anion Architecture Controls Structure and Electroresponsivity of Anhalogenous Ionic Liquids in a Sustainable Fluid.

Three nonhalogenated ionic liquids (ILs) dissolved in 2-ethylhexyl laurate (2-EHL), a biodegradable oil, are investigated in terms of their bulk and electro-interfacial nanoscale structures using small-angle neutron scattering (SANS) and neutron reflectivity (NR). The ILs share the same trihexyl(tetradecyl)phosphonium ([P6,6,6,14]+) cation paired with different anions, bis(mandelato)borate ([BMB]-), bis(oxalato)borate ([BOB]-), and bis(salicylato)borate ([BScB]-). SANS shows a high aspect ratio tubular self-assembly structure characterized by an IL core of alternating cations and anions with a 2-EHL-rich shell or corona in the bulk, the geometry of which depends upon the anion structure and concentration. NR also reveals a solvent-rich interfacial corona layer. Their electro-responsive behavior, pertaining to the structuring and composition of the interfacial layers, is also influenced by the anion identity. [P6,6,6,14][BOB] exhibits distinct electroresponsiveness to applied potentials, suggesting an ion exchange behavior from cation-dominated to anion-rich. Conversely, [P6,6,6,14][BMB] and [P6,6,6,14][BScB] demonstrate minimal electroresponses across all studied potentials, related to their different dissociative and diffusive behavior. A mixed system is dominated by the least soluble IL but exhibits an increase in disorder. This work reveals the subtlety of anion architecture in tuning bulk and electro-interfacial properties, offering valuable molecular insights for deploying nonhalogenated ILs as additives in biodegradable lubricants and supercapacitors.

Isolation and Characterization of Indigenous Bacteria with Purifying Potential in Solid Palm Oil Extraction Sludge Generated by SOCAPALM-Mbambou

The oil palm industry contributes significantly to the economic development of producing countries such as Cameroon. Unfortunately, the exploitation of palm oil constitutes a source of environmental pollution due to the production of enormous quantities of waste during its extraction process, including solid sludge generating greenhouse gases which contribute to global warming climatic. All this leads to the search for alternatives which consists of isolating and characterizing indigenous bacteria with biodegradation capacities in sludge from palm oil extraction. The pH and bacterial counts were determined by the potentiometric method and the decimal dilution technique, respectively. The isolated bacteria were identified by their cultural, cellular and biochemical characteristics. In addition, the identification of Gram- bacteria was further explored by the API 20 E gallery. The palm oil biodegradability test was carried out on M2 medium supplemented with 2% palm oil. The solid sludge biodegradability test was carried out on liquid MSM medium supplemented with 4% sludge stock solution. The results showed that the sludge sample had a slightly alkaline pH of 7.3. A bacterial load of around 10<sup>9</sup> CFU/g of soil was counted. Thirty-one bacterial strains were isolated and purified, including 12 <i>Bacillus sp</i>, 10 <i>Pseudomonas sp</i>, 8 <i>Proteus mirabilis</i> and 1 <i>Klebsiella pneumoniae</i>. All isolates tested for their ability to degrade palm oil or solid sludge grew in culture media with palm oil or solid sludge as the sole source of carbon and energy but with a difference in load. Thus, isolates BI2, BI5, BI31, BI10 and BI 9 showed the highest degradation capacities. These isolates could be used to constitute consortia of microorganisms that can be used in the treatment of waste generated by palm oil extraction.

Bacterial biodegradation of oil-contaminated soil for pollutant abatement contributing to achieve sustainable development goals: A comprehensive review

Petroleum hydrocarbon-induced environmental degradation has escalated, necessitating immediate remediation due to the ongoing growth of communities and modernization of civilization. Both carbon and energy can be obtained from hydrocarbons of petroleum, which are decomposed by a wide variety of microorganisms found in nature. Many times, remediation of places damaged by oil using biological means is accomplished by using bacteria that have such characteristics. Hence, this review attempt to highlight on the oil contaminated soil, source of oil pollution, the composition of oil, the impact of oil contamination on the living organisms additionally, the destiny of oil in the environment, how bacteria distributed in the soil and the most common degradable bacteria and their role in oil biodegradation with some attention on the impact of their enzymes. Also, considering the mechanism of biodegradation of aliphatic and aromatic oil hydrocarbon compounds, how bacteria taking up oil hydrocarbons and the influence of several elements on the processes of oil biodegradation. Furthermore, it; reducing pollution contributes to achieving sustainable development goals.

Evaluation of thermal damaged die steel through magnetic emission technique

This paper describes the potential of magnetic hysteresis loop (HL) technique to monitor the thermally damaged regions of hardened AISI H13 die steel. To overcomes this thermal damage issue, minimum quantity lubrication grinding with bio-lubricants like castor oil, biodegradable oil, and Al2O3 nanofluid was adopted. HL parameters i.e., average permeability and coercivity linearly correlated with average grain size, microhardness, and full width at half maximum (FWHM) and its correlational coefficient of ∼0.8959, ∼0.9661, ∼0.9278, ∼0.9652, ∼0.9485, and ∼0.9870, respectively. The alteration in the steepness of the HL envelope well agrees with the dominant role of microhardness and FWHM. It is concluded that an inspection of ground die steel during in-line production, HL should be calibrated concerning surface properties.

Crude Oil Biodegradation Performance in Natural Seawater of a Trichoderma species from Decaying Mangrove Wood in East Kalimantan

Large-scale petroleum production poses environmental and human health risks, particularly due to petroleum contamination in marine environments. The aim of this study was to isolate and screen fungi inhabiting decaying mangrove wood in East Kalimantan with their ability to degrade crude oil in seawater. In the initial step, fungi were isolated using standard methods and screened for crude oil degradation and biomass production. Selected fungi were based on their significant biomass production. Subsequently, the selected fungus was cultured in three types of media based on natural seawater and crude oil at initial concentrations ranging from 1% to 5% (v/v). The biodegradation of crude oil was assessed spectrophotometrically at 420 nm. Out of the 17 decaying wood fungi, MG-07 exhibited significantly higher biomass production compared to the control medium (without crude oil). Gas chromatography-mass spectrometry analysis indicated that MG-07 degraded 20%–80% of the normal aliphatic compounds in the tested crude oils within 2 weeks. Furthermore, the growth and degradation efficiency of MG-07 was significantly enhanced when cultured in a natural seawater medium containing crude oil, supplemented with glucose (20 g/L) and Tween 80 (1% v/v). The highest observed biomass gains were 867%, with a biodegradation efficiency of 31.6% at a crude oil concentration of 1%. MG-07 was identified as Trichoderma sp. based on the internal transcribed spacer region. The results obtained from this study demonstrate that MG-07 has significant potential for degrading crude oil in saline environments. These findings provide valuable insights for the application of fungi in marine oil spill remediation.

Geochemical Characteristic and Source Correlation of Biodegraded Oils from the Western Halaalate Area of Junggar Basin

The relationship between biodegraded oil and its source has long been a complex and contentious topic. The Western Halaalate area is located in the Piedmont area on the northwest margin of the Junggar Basin. Source rocks of the Fengcheng Formation exist both locally and in the nearby Mahu Depression. In order to determine the source of biodegraded crude oil in this area, the molecular marker characteristics of biodegraded crude oil were analyzed by gas chromatography-mass spectrometry. The results showed that the vitrinite reflectance (Ro) of source rocks of the Permian Fengcheng Formation in the nearby Mahu Depression is greater than 1.3% and has entered a high mature stage of condensate oil and moisture gas; the source rock of Permian Fengcheng Formation in Western Halaalate area is in a mature stage with Ro of 0.79%~1.13%. The ascending configuration of tricyclic terpenes C20-C21-C23 for the crude oil samples found in the Carboniferous strata of the Western Halaalate Area is consistent with the characteristics of the Fengcheng Formation source rocks, which are present in both the Western Halaalate Area and the nearby Mahu Depression. Chromatography spectrometry examination shows that crude oils have undergone a varying degree of biodegradation. The Carboniferous oil was originated from the in situ Fengcheng Formation source rocks based on the application of molecular markers resistant to biodegradation, such as maturity parameters, salinity parameters, the new gammacerane index, and aromatic hydrocarbon parameters, combined with the analysis of hydrocarbon migration pathway. In addition, the oil biodegradation alteration rules in the Western Halaalate area were clarified, which advances regional knowledge of the relationship between biodegraded oil and source rocks.

Immiscible Rayleigh–Taylor turbulence: Implications for bacterial degradation in oil spills

An unstable density stratification between two fluids mixes spontaneously under the effect of gravity, a phenomenon known as Rayleigh-Taylor (RT) turbulence. If the two fluids are immiscible, for example, oil and water, surface tension prevents intermixing at the molecular level. However, turbulence fragments one fluid into the other, generating an emulsion in which the typical droplet size decreases over time as a result of the competition between the rising kinetic energy and the surface energy density. Even though the first phenomenological theory describing this emulsification process was derived many years ago, it has remained elusive to experimental verification, hampering our ability to predict the fate of oil in applications such as deep-water spills. Here, we provide the first experimental and numerical verification of the immiscible RT turbulence theory, unveiling a unique turbulent state that originates at the oil-water interface due to the interaction of multiple capillary waves. We show that a single, non-dimensional, and time-independent parameter controls the range of validity of the theory. Our findings have wide-ranging implications for the understanding of the mixing of immiscible fluids. This includes in particular oil spills, where our work enables the prediction of the oil-water interface dynamics that ultimately determine the rate of oil biodegradation by marine bacteria.

Efficient biodegradation of crude oil by novel Pseudomonas aeruginosa strain isolated from petrochemical wastewater: identification and optimization

One of the most noticeable risks that challenge the lives of organisms and human health is the entry of petroleum compounds such as crude oil into the environment. Herein, a novel strain of crude oil-degrading bacteria, KSH-P1, identified from petrochemical wastewater was isolated and purified. The most efficient strain was identified by 16S rDNA sequencing which was used for the crude oil degradation experiments. The operational variables that affect degradation were optimized by response surface methodology based on a quadratic model achieved from a Box–Behnken design. The maximum biodegradation was determined at pH of 7.88, temperature of 35.54 °C, and yeast extract of 0.5 g/L. The model had R 2 , R adj 2 and R pred 2 values of 0.9966, 0.9906 and 0.9495, respectively. The crude oil biodegradation from petrochemical wastewater in the selected model experiments varied from 18.31% to 76.71%. The maximum biodegradation based on multiple response prediction of variables and validation test were 78.63% and 79.03%, including high prediction accuracy of the model to determine the optimal operating conditions of Strain-KSH-P1 for crude oil degradation. Considering the ability of KSH-P1 in the biodegradation of various crude oil compounds, the isolated strain can be used efficiently for the bioremediation of petroleum compounds.

<i>Aspergillus niger </i>АМ1 strain as causative agent for oil and petroleum products biodegradation

The biodegradation of oils by the strain Aspergillus niger AM1 VKM F-4815D was studied. Visual observation and gas chromatography-mass spectrometry showed that oil is subject to partial destruction, but cannot serve as the only source of carbon — the culture medium must contain glucose. An interesting fact is the change in consistency and hardening of oil under the influence of A. niger. This allows us to consider the possibility of using the strain for the bioremediation of soils and waters contaminated with oil. No less interesting is that, even earlier, the ability of the strain to metabolize a number of toxic phosphorus compounds, including even white and red phosphorus, was established. However, most organic solvents have a noticeable toxic effect, inhibiting growth in the presence of glucose and not becoming carbon sources in the absence of glucose.

Characterization of a biosurfactant produced by Peruvian strain Pseudomonas aeruginosa 6K‐11

AbstractBACKGROUNDThe oil industry has a big impact on the environment by itself and by using chemically synthesized surfactants. Biosurfactants are an ecofriendly alternative, especially rhamnolipids produced by Pseudomonas aeruginosa. Rhamnolipids in a determined concentration decrease the liquid surface tension, and this allows access oil hydrocarbon to be degraded. The objective of this research is to characterize the biosurfactant produced by the native strain P. aeruginosa 6K‐11 by determining its critical micelle concentration (CMC), Krafft point, and emulsifying activity.RESULTSExperiments were initially performed with rhamnolipid produced by P. aeruginosa 6K‐11 growing on Siegmund‐Wagner medium with 1% of waste oil as carbon source and at 31.26 °C, 186 rpm after 42 h of incubation. After that, the biosurfactant was purified according to acid precipitation methodology. The first conductivity measurement, 34 μS/cm, was obtained with 12.5 g/L of rhamnolipid by using an APERA conductivity meter. The rhamnolipid CMC was 5.86 g/L due to the conductivity measurements graph and 0.49 was the dissociation degree. The equations of both lines were found by the method of least squares. The rhamnolipid has produced 1.97 Units of Emulsifying Activity (UEA) and 50% stability was observed based on the E24 Index. The highest conductivity achieved under 39 °C, as calculated from a conductivity against temperature graph, was the Krafft point.CONCLUSIONThese findings give important parameters to characterize the P. aeruginosa 6K‐11 biosurfactant activity that can be used to accelerate oil biodegradation in bioremediation processes. © 2024 Society of Chemical Industry (SCI).

Flotation and oil agglomeration of high ash LVMC coal after deshaling by jigging: a comparative study using different collectors

ABSTRACT LVMC coal with an ash content of 38.70% was initially crushed to −4.0 to +0.50 mm and deshaled using a laboratory model Batac Jig. The resulting concentrate was further size reduced to −0.50 mm and combined with the original fines obtained during crushing. Froth flotation (of −0.50 mm size) and oil agglomeration (of −0.075 mm size) tests conducted using different collectors at varying dosages revealed that the combination of jigging and froth flotation processes can effectively reduce the ash content down to 26.29%. At this stated ash, an acceptable yield of 54.67% was obtained with the highest Separation Efficiency value of 18.20 when the Mahua oil collector was used. Kinetic studies of batch flotation indicated that both ash and non-ash components of the coal reported to concentrate at the same rates, demonstrated by the relative ratios of rate constants ( K N A K A ) , which was equal to 1.0404. It is concluded in the paper that the collector mahua oil outperformed in both the flotation and oil agglomeration processes. The uniqueness of the paper is the approach of beneficiating the newly graded high-high, high-NGM Indian coal using cost-effective bio-degradable oils after deshaling in a Jig. The characteristic size distribution curve plotted for the agglomerates is defined mathematically.

Toward Effects of Hydrophobicity on Biosurfactant Production by Bacillus subtilis Isolates from Crude-Oil-Exposed Environments

Background: Due to their structural features, biosurfactants reveal promising physicochemical properties, making them interesting for various applications in different fields, such as the food, cosmetics, agriculture, and bioremediation sectors. In particular, the bioproduction of surfactin, one of the most potent microbially synthesized biosurfactant molecules, is of great interest. However, since the wild-type productivities are comparably low, stimulatory environmental conditions have to be identified for improved bioproduction This study aims to find a correlation between the hydrophobicity and production of the biosurfactant surfactin by B. subtilis isolates from crude-oil-contaminated soil and water. Methods: The surfactin production yield was characterized in adapted batch cultivations using high-performance thin-layer liquid chromatography (HPTLC). Defined hydrophobic environmental conditions were achieved by supplementation with hexadecane or polystyrene beads, and the effects on biosurfactant production were measured. Adaptations at the protein level were analyzed using mass spectrometry measurements. Results: The correlation between hydrophobicity and surfactin production was characterized using Bacillus subtilis strains ZH1 and P7 isolated from crude-oil-contaminated soil and water. Since these isolates show the biodegradation of crude oil and hexadecane as hydrophobic substrates, respectively, a first-time approach, using polystyrene beads, was applied to provide a hydrophobic environment. Interestingly, contrary to popular opinion, reduced biosurfactant production was determined. Using mass spectrometric approaches, the physiological effects of co-cultivation and the cellular response at the protein level were investigated, resulting in altered quantities of stress proteins and proteins involved in the carbon metabolism counter to polystyrene beads. Conclusions: Contrary to common opinion, increasing hydrophobicity does not have a stimulating effect, and even reduces the effect on the bioproduction of surfactin as the main biosurfactant using selected B. subtilis strains.

Isolation and characterization of Candida tropicalis B: a promising yeast strain for biodegradation of petroleum oil in marine environments

The increasing interest in environmental protection laws has compelled companies to regulate the disposal of waste organic materials. Despite efforts to explore alternative energy sources, the world remains heavily dependent on crude petroleum oil and its derivatives. The expansion of the petroleum industry has significant implications for human and environmental well-being. Bioremediation, employing living microorganisms, presents a promising approach to mitigate the harmful effects of organic hydrocarbons derived from petroleum. This study aimed to isolate and purify local yeast strains from oil-contaminated marine water samples capable of aerobically degrading crude petroleum oils and utilizing them as sole carbon and energy sources. One yeast strain (isolate B) identified as Candida tropicalis demonstrated high potential for biodegrading petroleum oil in seawater. Physiological characterization revealed the strain’s ability to thrive across a wide pH range (4–11) with optimal growth at pH 4, as well as tolerate salt concentrations ranging from 1 to 12%. The presence of glucose and yeast extract in the growth medium significantly enhanced the strain's biomass formation and biodegradation capacity. Scanning electron microscopy indicated that the yeast cell diameter varied based on the medium composition, further emphasizing the importance of organic nitrogenous sources for initial growth. Furthermore, the yeast strain exhibited remarkable capabilities in degrading various aliphatic and aromatic hydrocarbons, with a notable preference for naphthalene and phenol at 500 and 1000 mg/l, naphthalene removal reached 97.4% and 98.6%, and phenol removal reached 79.48% and 52.79%, respectively. Optimization experiments using multi-factorial sequential designs highlighted the influential role of oil concentration on the bioremediation efficiency of Candida tropicalis strain B. Moreover, immobilized yeast cells on thin wood chips demonstrated enhanced crude oil degradation compared to thick wood chips, likely due to increased surface area for cell attachment. These findings contribute to our understanding of the potential of Candida tropicalis for petroleum oil bioremediation in marine environments, paving the way for sustainable approaches to address oil pollution.

Anaerobic hydrocarbon biodegradation by alkylotrophic methanogens in deep oil reservoirs.

In subsurface biodegraded oil reservoirs, methanogenic biodegradation of crude oil is a common process. This process was previously assigned to the syntrophy of hydrocarbon-degrading bacteria and methanogenic archaea. Recent studies showed that archaea of the Candidatus Methanoliparum named as alkylotrophic methanogens couple hydrocarbon degradation and methane production in a single archaeon. To assess the geochemical role of Ca. Methanoliparum, we analyzed the chemical and microbial composition and metabolites of 209 samples from 15 subsurface oil reservoirs across China. Gas chromatography-mass spectrometry analysis revealed that 92% of the tested samples were substantially degraded. Molecular analysis showed that 85% of the tested samples contained Ca. Methanoliparum, and 52% of the tested samples harbored multiple alkyl-coenzyme M derivatives, the intercellular metabolites of alkylotrophic archaea. According to metagenomic and metatranscriptomic analyses, Ca. Methanoliparum dominates hydrocarbon degradation in biodegraded samples from the Changqing, Jiangsu, and Shengli (SL) oilfields, and it is persistently present as shown in a 15-year-long sampling effort at the Shengli oilfield. Together, these findings demonstrate that Ca. Methanoliparum is a widely distributed oil degrader in reservoirs of China, suggesting that alkylotrophic methanogenesis by archaea plays a key role in the alteration of oil reservoirs, thereby expanding our understanding of biogeochemical process in the deep biosphere.

Synergistic dispersion and biodegradation of oil in seawater based on Janus nanosheets and oil-degrading bacteria

Janus nanosheets synergistically interact with oil-degrading bacteria for marine oil spill remediation.

Performance evaluation of hybrid biodegradable oils as a lubricant during cylindrical turning of AISI 304 austenitic stainless steel

<abstract> <p>In the engineering sector, machining plays a significant role. The ability of the cutting zone to dissipate heat has grown in importance for the machining industry’s sustainability. Government legislation is pushing the industry to use fewer conventional lubricants as concerns about the effects on the environment and human health grow. This shifts attention to Minimum Quantity Lubrication (MQL) and biodegradable oils. The purpose of this study is to show how well two vegetable oils, in their raw forms, perform as cutting fluids during the MQL turning process of AISI 304 stainless steel. Each vegetable oil’s physiochemical and lubricating qualities were examined separately. After that, the two oils that comprised the hybrid vegetable oil were blended at a ratio of 0.5:0.5. During machining with an external threading tool, the hybrid vegetable oil was compared to its equivalent mineral-based oil in terms of cutting temperature and surface roughness. The Taguchi L9 orthogonal array was used in the study. According to the data, the cutting temperature was lowest when cutting with mineral oil, and highest when cutting with a hybrid mixture. In general, the mineral oil produced a reduced surface roughness compared to the vegetable oil mixture by about 68.6%. The combo of palm kernel and yellow orleander oil marginally outperformed mineral by about 2.3% when it came to cutting temperature. The significance of this study is to develop a more sustainable and environmentally friendly lubricants for industrial applications.</p> </abstract>

Crude oil biodegradation potential of lipase produced by Bacillus subtilis and Pseudomonas aeruginosa isolated from hydrocarbon contaminated soil

Microbial biodegradation of oil pollutants and their derivatives has become the most environmental-friendly method in the developing world. The aim of this study was to evaluate crude oil biodegradation potential of lipase produced by indigenous bacteria from oil contaminated soil. Indigenous bacteria isolates were identified as species of Bacillus subtilis and Pseudomonas aeruginosa, the isolates were able to produce lipase as revealed in their zone of clearance on tween 80 agar plates and the presence of lipase produced by the two bacteria were further confirmed using spectrophotometric analyses. Lipase produced by B. subtilis showed maximal lipase activity at pH 8 and 40°C while the enzyme produced by P. aeruginosa showed maximal lipase activity (U/mL) at pH 8 and 50°C when subjected to various pH and temperature respectively. Lipase produced by B. subtilis recorded 8.11 ± 0.70% of crude oil degradation in mineral salt medium within 28 days, while that of P. aeruginosa recorded 15.6 ± 0.03% of crude oil biodegradation. The GC–MS analysis of the crude oil treatment showed complete mineralization of several compounds, and also showed peak reduction which indicates lipase efficiency in the degradation of hydrocarbons. As revealed by GC–MS analysis, out of the 8 hydrocarbons identified in an undegraded oil, 5 were completely degraded by the enzyme activities while 2 (toluene and methyl, cyclopentane) were identified with hydrocarbons treated with lipase. The enzymes produced by B. subtilis and P. aeruginosa can serve as useful product for bioremediation of crude oil contaminated soil.

Comparative characterization of anaerobic oil oxidation processes by microbial communities of sediments from natural oil seeps in Lake Baikal (Gorevoy Utes, Bolshaya Zelenovskaya)

The comparative characterization of oil biodegradation processes under anaerobic conditions during the cultivation of microbial communitiesof sediments from two sites of oil seeps is given. The microbial community of sediments from the Bolshaya Zelenovskaya River oil seep, functioning under the conditions of long-term exposure to hydrocarbons, is focused more on the processes of anaerobic oxidation of oil in comparison with the microbial communities of sediments from the oil seep located near Cape Gorevoy Utes. This is evidenced by the high level of hydrocarbon biodegradation in both surface and deep sediments, regardless of the electron acceptors present in the medium. Oil degradation in enrichment cultures was accompanied by the formation of hydrocarbon gases (methane and ethane). The highest concentration of methane formed was found in the experiment with sediments from Cape Gorevoy Utes. Ethane generation, on the contrary, was more typical of the cultivation of communities from sediments of the Bolshaya Zelenovskaya River. Microbial communities functioning under anaerobic conditions in sediments at the sites of oil seeps are no less important in the processes of self-purification of the lake from oil “pollution” than aerobic microbial communities of the water column and surface sediments.

Comparison of physical properties of ferrofluids based on mineral transformer oil and bio-degradable gas-to-liquid oil

Ferrofluids based on mineral transformer oil have been intensively studied over two decades owing to their outstanding thermal and electrical insulating properties. However, current environmental demands on transformer operation give priority to the use of biodegradable transformer oils. Clearly, the differences in physical properties of biodegradable oils and those refined from crude oil determine the physical properties of ferrofluids based on the two types of oils. In this study, ferrofluids with various concentrations of iron oxide nanoparticles have been prepared on mineral transformer oil (M−oil) and biodegradable transformer oil based on gas-to-liquid technology (S-oil). The ferrofluids were subjected to experimental investigation of magnetization, AC magnetic susceptibility, thermal conductivity, viscosity and dielectric response. Based on zero-field-cooled and field-cooled magnetization curves, a lower temperature of a specific magnetization maximum associated with the melting of the oil (phase transition) was found for M−samples than for S-samples. The effect of carrier liquid on the onset of extrinsic superparamagnetism in addition to the intrinsic superparamagnetism is observed. Spectra of AC magnetic susceptibility of both types of ferrofluids exhibit quasi constant behaviour with amoderate decrease at high frequencies of amagnetic field. The viscosity of M−samples is slightly higher than that of S-samples. On the other hand, M−samples exhibit lower thermal conductivity than S-samples. In both cases, the thermal conductivity linearly decreases with temperature. Dielectric spectroscopy has revealed remarkable dielectric dispersion below 100 Hz in both ferrofluid types. The relaxation has been ascribed to interfacial polarization, which can be considered as a serious drawback from an electrical engineering application point of view. The measured physical properties of the ferrofluids are analyzed in regard to the density and viscosity of the base oils.

Microbial diversity and oil biodegradation potential of northern Barents Sea sediments

The Arctic, an essential ecosystem on Earth, is subject to pronounced anthropogenic pressures, most notable being the climate change and risks of crude oil pollution. As crucial elements of Arctic environments, benthic microbiomes are involved in climate-relevant biogeochemical cycles and hold the potential to remediate upcoming contamination. Yet, the Arctic benthic microbiomes are among the least explored biomes on the planet. Here we combined geochemical analyses, incubation experiments, and microbial community profiling to detail the biogeography and biodegradation potential of Arctic sedimentary microbiomes in the northern Barents Sea. The results revealed a predominance of bacterial and archaea phyla typically found in the deep marine biosphere, such as Chloroflexi, Atribacteria, and Bathyarcheaota. The topmost benthic communities were spatially structured by sedimentary organic carbon, lacking a clear distinction among geographic regions. With increasing sediment depth, the community structure exhibited stratigraphic variability that could be correlated to redox geochemistry of sediments. The benthic microbiomes harbored multiple taxa capable of oxidizing hydrocarbons using aerobic and anaerobic pathways. Incubation of surface sediments with crude oil led to proliferation of several genera from the so-called rare biosphere. These include Alkalimarinus and Halioglobus, previously unrecognized as hydrocarbon-degrading genera, both harboring the full genetic potential for aerobic alkane oxidation. These findings increase our understanding of the taxonomic inventory and functional potential of unstudied benthic microbiomes in the Arctic.