In situ microbial remediation of crude oil-soaked marine sediments using zeolite carrier with a polymer coating

Whole genome sequencing and analysis of benzo(a)pyrene-degrading bacteria Bacillus cereus M72-4

Benzo(a)pyrene produced by food during high-temperature process enters the body through ingestion, which causes food safety issues to the human body. To alleviate the harm of foodborne benzo(a)pyrene to human health, a strain that can degrade benzo(a)pyrene was screened from Kefir, a traditional fermented product in Xinjiang. Bacillus cereus M72-4 is a Gram-positive bacteria sourced from Xinjiang traditional fermented product Kefir; under benzo(a)pyrene stress conditions, there was 69.39% degradation rate of 20 mg/L benzo(a)pyrene by strain M72-4 after incubation for 72 h. The whole genome of M72-4 was sequenced using PacBio sequencing technology in this study. The genome size was 5754 801 bp and a GC content was 35.24%; a total of 5719 coding genes were predicted bioinformatically. Through functional database annotation, it was found that the strain has a total of 219 genes involved in the transportation and metabolism of hydrocarbons, a total of 9 metabolic pathways related to the degradation and metabolism of exogenous substances, and a total of 67 coding genes. According to the Kyoto Encyclopedia of Genes and Genomes database annotation results, a key enzyme related to benzo(a)pyrene degradation, catechol 2,3-dioxygenase, was detected in the genome data of Bacillus cereus M72-4, encoding genes dmpB and xylE, respectively. There are also monooxygenases and dehydrogenases. Therefore, it can be inferred that this strain mainly degrades benzo(a)pyrene through benzoate metabolic.

Enhanced bioremediation of cyclohexaneacetic acid in offshore sediments with green synthetic iron oxide and Pseudoalteromonas sp

Naphthenic acids (NAs) have been found to exert serious threats on offshore sediment ecosystems and human health in recent years, which entails us the urgent need for NAs remediation. Bioremediation is considered an ideal method for sediment remediation due to ecological sustainability and economic feasibility. However, current bioremediation efficiency of offshore sediments suffers from relatively slow and there has never any attempts to bioremediate offshore sediment NAs contamination hitherto. In this study, the green synthetic iron oxides (gFeOx) based on Laminaria extracts was employed to enhance the biodegradation of NAs (Cyclohexylacetic acid, CHAA) in offshore sediments by Pseudoalteromonas sp. JSTW (an indigenous microorganism). The results showed that CHAA (20 mg·kg-1) in offshore sediments was removed almost 100% within 7 days at 30 mg·kg-1 gFeOx and 0.6 mg·kg-1 Strain JSTW. High-throughput sequencing results revealed that the structure and function of sediment microbial community were essentially restored to uncontaminated levels after bioremediation, highlighting the joint remediation approach is an efficient and eco-friendly method. Overall, this work has firstly provided insights into the application for NAs in situ bioremediation in offshore sediments.

Transcriptomic and biochemical analysis of metabolic remodeling in Bacillus subtilis MSC4 under Benzo[a]pyrene stress

Polyaromatic benzo[a]pyrene (B[a]P) is a toxic carcinogenic environmental pollutant, and the use of microorganisms to remediate B[a]P contamination is considered to be one of the most effective strategies. However, there is still a gap in studying the metabolic remodeling of microorganisms under B[a]P stress. In this study, our systematically investigated the effects of B[a]P on the metabolism of Bacillus subtilis MSC4 based on transcriptomic, molecular and biochemical analyses. The results showed that in response to B[a]P stress, MSC4 formed more biofilm matrix and endospores, the structure of the endospores also was changed, which led to a reduction in their resistance and made them more difficult to germinate. In addition to an increase in glycolysis activity, the activities of tricarboxylic acid cycle, pentose phosphate pathway and the electron transport chain were decreased. B[a]P stress forced MSC4 to strengthen arginine synthesis, urea cycle, and urea decomposition, meanwhile, synthesize more ribonucleotides. The activity of DNA replication, transcription activities and the expression of multiple ribosomal protein genes were reduced. Moreover, all of the reported enzymes involved in B[a]P degradation showed decreased transcript abundance, and the degradation of B[a]P caused significant up-regulation of the gene expression of the acid inducible enzyme OxdC and the synthesis of acetoin. In addition, the cytotoxicity of B[a]P to bacteria was directly displayed in four aspects: increased intracellular level of reactive oxygen species (ROS), elevated cell membrane permeability, up-regulation of the cell envelope stress-sensing two-component system LiaRS, and downregulation of siderophores biosynthesis. Finally, B[a]P also caused morphological changes in the cells, with some cells exhibiting significant deformation and concavity. These findings provide effective research directions for targeted improvement the cellular activity of B[a]P-degrading strains, and is beneficial for further application of microorganisms to remediate B[a]P -contaminated soils.

Oil-Contaminated Soil Remediation with Biodegradation by Autochthonous Microorganisms and Phytoremediation by Maize (Zea mays)

Biological methods are currently the most commonly used methods for removing hazardous substances from land. This research work focuses on the remediation of oil-contaminated land. The biodegradation of aliphatic hydrocarbons and PAHs as a result of inoculation with biopreparations B1 and B2 was investigated. Biopreparation B1 was developed on the basis of autochthonous bacteria, consisting of strains Dietzia sp. IN118, Gordonia sp. IN101, Mycolicibacterium frederiksbergense IN53, Rhodococcus erythropolis IN119, Rhodococcus globerulus IN113 and Raoultella sp. IN109, whereas biopreparation B2 was enriched with fungi, such as Aspergillus sydowii, Aspergillus versicolor, Candida sp., Cladosporium halotolerans, Penicillium chrysogenum. As a result of biodegradation tests conducted under ex situ conditions for soil inoculated with biopreparation B1, the concentrations of TPH and PAH were reduced by 31.85% and 27.41%, respectively. Soil inoculation with biopreparation B2 turned out to be more effective, as a result of which the concentration of TPH was reduced by 41.67% and PAH by 34.73%. Another issue was the phytoremediation of the pre-treated G6-3B2 soil with the use of Zea mays. The tests were carried out in three systems (system 1-soil G6-3B2 + Zea mays; system 2-soil G6-3B2 + biopreparation B2 + Zea mays; system 3-soil G6-3B2 + biopreparation B2 with γ-PGA + Zea mays) for 6 months. The highest degree of TPH and PAH reduction was obtained in system 3, amounting to 65.35% and 60.80%, respectively. The lowest phytoremediation efficiency was recorded in the non-inoculated system 1, where the concentration of TPH was reduced by 22.80% and PAH by 18.48%. Toxicological tests carried out using PhytotoxkitTM, OstracodtoxkitTM and Microtox® Solid Phase tests confirmed the effectiveness of remediation procedures and showed a correlation between the concentration of petroleum hydrocarbons in the soil and its toxicity. The results obtained during the research indicate the great potential of bioremediation practices with the use of microbial biopreparations and Zea mays in the treatment of soils contaminated with petroleum hydrocarbons.

Biodegradation of Petroleum Sludge by Methylobacterium sp. Strain ZASH

A bacterium was isolated from sludge-contaminated soil in a petroleum refinery and tested for its ability to degrade aliphatic hydrocarbon compounds present in petroleum sludge. The isolate was grown on minimal salt media agar supplemented with 1% (w/v) petroleum sludge. The isolate was tentatively identified as Methylobacterium s p. s t rain ZASH based on the partial 16s rDNA molecular phylogeny. The bacterium grew optimally between the temperatures of 30°C and 35°C, pH 7 and 7.5, 0.5% and 1.5% (v/v) Tween 80 as the surfactant, and between 1% and 2% (w/v) peptone as the nitrogen source. The constants derived from the Haldane equation were μmax = 0.039 hr-1, Ks = 0.385% (w/v) total petroleum hydrocarbons (TPH) or 3,850 mg/L TPH, and Ki =1.12% (w/v) TPH or 11,200 mg/L. The maximum biodegradation rate exhibited by this strain was 19 mg/L/hr at an initial TPH concentration of 10,000 mg/L. Gas chromatography analysis revealed that after 15 days the strain was able to degrade all aliphatic n-alkanes investigated with different efficiencies. Shorter n-alkanes were generally degraded more rapidly than longer n-alkanes with 90% removal for C-12 compared to only 30% removal for C-36. The addition of sawdust did not improve bacterial degradation of petroleum hydrocarbons, but it assisted in the removal of remaining undegraded hydrocarbons through adsorption.

Application of graphene aerogels in oil spill recovery: A review

Oil spills have long been a serious threat to marine environment. Physical recovery is the safest and most efficient method in the emergency disposal of offshore oil spill. Graphene aerogel (GA) has a wide application prospect in offshore oil spill emergency recovery and disposal given its unique structural characteristics. In this article, the preparation methods of GA adsorbent are summarized. On this basis, in the background of the application of offshore oil spill recovery, the related properties and targeted modification schemes of GA, such as adsorption, mechanical, and magnetic properties, as well as photothermal conversion properties for disposal of oil spills with high viscosity, are discussed. The Joule heating/photothermal conversion scheme can improve the recovery efficiency of offshore high viscosity oil spills, and adding metal composite materials can increase the magnetic performance and surface roughness of GA and facilitate positioning and recovery after offshore oil spills disposal. The challenges and prospects of modification research are also highlighted, and guidance for further optimizing the performance of GA in offshore oil spill recovery is provided.

Proteomic response of Pseudomonas aeruginosa IIPIS-8 during rapid and efficient degradation of naphthalene

Polycyclic aromatic hydrocarbons (PAHs) are widely distributed in the ecosystem and are of significant concern due to their toxicity and mutagenicity. Bioremediation of PAHs is a popular and benign approach that ameliorates the environment. This study investigated the biodegradation and proteome response of Pseudomonas aeruginosa IIPIS-8 for two-ringed PAH: naphthalene (NAP) to understand proteome alteration during its bioremediation. Rapid biodegradation was observed up to 98 ± 1.26% and 84 ± 1.03%, respectively, for initial concentrations of 100 mg L^-1 and 500 mg L^-1 of NAP. Degradation followed first-order kinetics with rate constants of 0.12 h^-1 and 0.06 h^-1 and half-life (t_1/2) of 5.7 h and 11.3 h, respectively. Additionally, the occurrence of key ring cleavage and linear chain intermediates, 2,3,4,5,6, -pentamethyl acetophenone, 1-octanol 2-butyl, and hexadecanoic acid supported complete NAP degradation. Proteomics study of IIPIS-8 throws light on the impact of protein expression, in which 415 proteins were quantified in sequential windowed acquisition of all theoretical fragment ion mass spectra (SWATH-MS) analysis, of which 97 were found to be significantly up-regulated and 75 were significantly down-regulated by ≥ 2-fold change (p values ≤ 0.05), during the NAP degradation. The study also listed the up-regulation of several enzymes, including oxido-reductases, hydrolases, and catalases, potentially involved in NAP degradation. Overall, differential protein expression, through proteomics study, demonstrated IIPIS-8's capability to efficiently assimilate NAP in their metabolic pathways even in a high concentration of NAP.

Hydrocarbon Degradation and Microbial Survival Improvement in Response to γ-Polyglutamic Acid Application

To improve the environmental sustainability of cleanup activities of contaminated sites there is a need to develop technologies that minimize soil and habitat disturbances. Cleanup technologies, such as bioremediation, are based on biological products and processes, and they are important for the future of our planet. We studied the potential of γ-poly glutamic acid (PGA) as a natural component of biofilm produced by Bacillus sp. to be used for the decomposition of petroleum products, such as heavy naphtha (N), lubricating oil (O), and grease (G). The study aimed to assess the impact of the use of different concentrations of PGA on the degradation process of various fractions of petroleum hydrocarbons (PH) and its effect on bacterial population growth in harsh conditions of PH contamination. In laboratory conditions, four treatments of PGA with each of the petroleum products (N, O, and G) were tested: PGA₀ (reference), PGA₁ (1% PGA), PGA_1B (1% PGA with Bacillus licheniformis), and PGA₁₀ (10% PGA). After 7, 28, 56, and 112 days of the experiment, the percentage yield extraction, hydrocarbon mass loss, geochemical ratios, pH, electrical conductivity, and microorganisms survival were determined. We observed an increase in PH removal, reflected as a higher amount of extraction yield (growing with time and reaching about 11% in G) and loss of hydrocarbon mass (about 4% in O and G) in all treatments of the PGA compared to the reference. The positive degradation impact was intensive until around day 60. The PH removal stimulation by PGA was also reflected by changes in the values of geochemical ratios, which indicated that the highest rate of degradation was at the initial stage of the process. In general, for the stimulation of PH removal, using a lower (1%) concentration of PGA resulted in better performance than a higher concentration (10%). The PH removal facilitated by PGA is related to the anionic homopoliamid structure of the molecule and its action as a surfactant, which leads to the formation of micelles and the gradual release of PH absorbed in the zeolite carrier. Moreover, the protective properties of PGA against the extinction of bacteria under high concentrations of PH were identified. Generally, the γ-PGA biopolymer helps to degrade the hydrocarbon pollutants and stabilize the environment suitable for microbial degraders development.

Degradation potential of alkanes by diverse oil-degrading bacteria from deep-sea sediments of Haima cold seep areas, South China Sea

Marine oil spills are a significant concern worldwide, destroying the ecological environment and threatening the survival of marine life. Various oil-degrading bacteria have been widely reported in marine environments in response to marine oil pollution. However, little information is known about culturable oil-degrading bacteria in cold seep of the deep-sea environments, which are rich in hydrocarbons. This study enriched five oil-degrading consortia from sediments collected from the Haima cold seep areas of the South China Sea. Parvibaculum, Erythrobacter, Acinetobacter, Alcanivorax, Pseudomonas, Marinobacter, Halomonas, and Idiomarina were the dominant genera. Further results of bacterial growth and degradation ability tests indicated seven efficient alkane-degrading bacteria belonging to Acinetobacter, Alcanivorax, Kangiella, Limimaricola, Marinobacter, Flavobacterium, and Paracoccus, whose degradation rates were higher in crude oil (70.3–78.0%) than that in diesel oil (62.7–66.3%). From the view of carbon chain length, alkane degradation rates were medium chains > long chains > short chains. In addition, Kangiella aquimarina F7, Acinetobacter venetianus F1, Limimaricola variabilis F8, Marinobacter nauticus J5, Flavobacterium sediminis N3, and Paracoccus sediminilitoris N6 were first identified as oil-degrading bacteria from deep-sea environments. This study will provide insight into the bacterial community structures and oil-degrading bacterial diversity in the Haima cold seep areas, South China Sea, and offer bacterial resources to oil bioremediation applications.

Superhydrophobic Nanodiamond-Functionalized Melamine Sponge for Oil/Water Separation

Fabrication of absorbent materials foroil/water separation is an important ecological pursuit for oil spill clean-up and organic pollutants' removal. In this study, nanodiamonds (NDs), a promising member of the carbon family, were functionally modified by the covalent linking of octadecylamine (ODA). Subsequently, the superhydrophobic sponge with hierarchical microstructures was fabricated by embedding ND-ODA into a melamine sponge (MS) skeleton via a simple immersion-drying process. The as-prepared sponge (ND-ODA@PDMS@MS) showed superhydrophobic properties with a water contact angle of 155 ± 2°. For various oils and organic solvents, ND-ODA@PDMS@MS possesses excellent absorption capacity (26.65-55.64 g/g) and oil/water separation efficiency (above 98.6%). Furthermore, the adsorption capacity to crude oil remained relatively stable in highly acidic, alkaline, and salty conditions, ensuring the application in the clean-up of industrial oily sewages and marine oil spills. Besides absorbing oil for a single time, ND-ODA@PDMS@MS also exhibited satisfactory performance in continuous oil/water separation. Therefore, this work provides a facile strategy to produce robust and efficient absorbent materials for oil/water separation in large-scale oil and organic solvent clean-ups.

Characterization and biodegradation of ternary blends of lignosulfonate/synthetic zeolite/polyvinylpyrrolidone for agricultural chemistry

This study investigates novel ternary polymer blends based on polyvinylpyrrolidone (PVP) as the matrix in combination with lignosulfonate and synthetic zeolite. The blends were prepared by the casting method, and their properties were analysed by various techniques, i.e. FTIR analysis, differential scanning calorimetry and thermogravimetric analysis, including tests for water solubility and uptake, and determination of adhesion and hardness. The biodegradation of the blends in soil was also evaluated, and an experiment was conducted on plant growth (Sinapis alba). Optical microscopy showed that particles of the synthetic zeolite were relatively evenly distributed in the polymer matrix, forming random networks therein. The FTIR spectra for the blends proved that hydrogen bonding interactions had occurred between the PVP/synthetic zeolite and PVP/lignosulfonate. DSC analysis confirmed the good miscibility of the PVP and lignosulfonate. TGA results indicated that the thermal stability of the PVP was maintained. Lignosulfonate had the effect of reducing the adhesion of the blends. However, it was revealed that effect depends greatly on the presence of zeolite and the concentration of lignosulfonate. The obtained results showed that the optimal composition of the blend is 2.5 wt% of zeolite and 5 wt% of lignosulfonate into the PVP. Its water solubility and uptake was satisfactory from the perspective of handling and further utilization. A respirometric biodegradation test confirmed that the ternary blend was environmentally friendly, in addition to which a germination experiment evidenced that the lignosulfonate and synthetic zeolite promoted the root growth and development of S. alba. From these findings it was concluded that the novel ternary polymer blend was applicable as either as seed carriers (in the form of seed tapes) or as a biocompatible coating to protect seeds.

A global survey reveals a divergent extradiol dioxygenase clade as a widespread complementary contributor to the biodegradation of mono- and polycyclic aromatic hydrocarbons

Extradiol dioxygenation is a key reaction in the microbial aerobic degradation of mono- and polycyclic aromatic hydrocarbon catecholic derivatives. It has been reported that many bacterial enzymes exhibiting such converging functions act on a wide range of catecholic substrates. The present study reports a new subfamily of extradiol dioxygenases (EXDOs) with broad substrate specificity, the HrbC EXDOs. The new clade belongs to the XII cluster within family 2 of the vicinal oxygen chelate superfamily (EXDO-VC2), which is typically characterized by a preference for bicyclic substrates. Coding hrbC orthologs were isolated by activity-based screening of fosmid metagenomic libraries from large DNA fragments derived from heavily PAH-contaminated soils. They occurred as solitary genes within conserved sequences encoding enzymes for amino acid metabolism and were stably maintained in the chromosomes of the Betaproteobacteria lineages harboring them. Analysis of contaminated aquifers revealed coexpression of hrbC as a polycistronic mRNA component. The predicted open reading frames were verified by cloning and heterologous expression, confirming the expected molecular mass and meta-cleavage activity of the recombinant enzymes. Evolutionary analysis of the HrbC protein sequences grouped them into a discrete cluster of 1,2-dihydroxynaphthalene dioxygenases represented by a cultured PAH degrader, Rugosibacter aromaticivorans strain Ca6. The ecological importance and relevance of the new EXDO genes were confirmed by PCR-based mapping in different biogeographical localities contaminated with a variety of mono- and polycyclic aromatic compounds. The cosmopolitan distribution of hrbC in PAH-contaminated aquifers supports our hypothesis about its auxiliary role in the degradation of toxic catecholic intermediates, contributing to the composite EXDO catabolic capacity of the world's microbiomes.

An insight on microbial degradation of benzo[a]pyrene: current status and advances in research

Benzo[a]pyrene (BaP) is a high molecular weight polycyclic aromatic hydrocarbon produced as a result of incomplete combustion of organic substances. Over the years, the release of BaP in the atmosphere has increased rapidly, risking human lives. BaP can form bonds with DNA leading to the formation of DNA adducts thereby causing cancer. Therefore addressing the problem of its removal from the environment is quite pertinent though it calls for a very cumbersome and tedious process owing to its recalcitrant nature. To resolve such issues many efforts have been made to develop physical and chemical technologies of BaP degradation which have neither been cost-effective nor eco-friendly. Microbial degradation of BaP, on the other hand, has gained much attention due to added advantage of the high level of microbial diversity enabling great potential to degrade the substance without impairing environmental sustainability. Microorganisms produce enzymes like oxygenases, hydrolases and cytochrome P450 that enable BaP degradation. However, microbial degradation of BaP is restricted due to several factors related to its bio-availability and soil properties. Technologies like bio-augmentation and bio-stimulation have served to enhance the degradation rate of BaP. Besides, advanced technologies such as omics and nano-technology have opened new doors for a better future of microbial degradation of BaP and related compounds.

Evaluation of the Effectiveness of the Biopreparation in Combination with the Polymer γ-PGA for the Biodegradation of Petroleum Contaminants in Soil

Biodegradation is a method of effectively removing petroleum hydrocarbons from the natural environment. This research focuses on the biodegradation of aliphatic hydrocarbons, monoaromatic hydrocarbons such as benzene, toluene, ethylbenzene, and all three xylene isomers (BTEX) and polycyclic aromatic hydrocarbons (PAHs) as a result of soil inoculation with a biopreparation A1 based on autochthonous microorganisms and a biopreparation A1 with the addition of γ-PGA. The research used biopreparation A1 made of the following strains: Dietzia sp. IN133, Gordonia sp. IN138 Mycolicibacterium frederiksbergense IN53, Rhodococcus erythropolis IN119, Rhodococcus sp. IN136 and Pseudomonas sp. IN132. The experiments were carried out in laboratory conditions (microbiological tests, respirometric tests, and in semi-technical conditions (ex-situ prism method). The biodegradation efficiency was assessed on the basis of respirometric tests, chromatographic analyses and toxicological tests. As a result of inoculation of AB soil with the biopreparation A1 within 6 months, a reduction of total petroleum hydrocarbons (TPH) (66.03%), BTEX (80.08%) and PAHs (38.86%) was achieved and its toxicity was reduced. Inoculation of AB soil with the biopreparation A1 with the addition of γ-PGA reduced the concentration of TPH, BTEX and PAHs by 79.21%, 90.19%, and 51.18%, respectively, and reduced its toxicity. The conducted research has shown that the addition of γ-PGA affects the efficiency of the biodegradation process of petroleum pollutants, increasing the degree of TPH biodegradation by 13.18%, BTEX by 10.11% and PAHs by 12.32% compared to pure biopreparation A1.

Bioaugmentation with zeolite-immobilized bacterial consortium OPK results in a bacterial community shift and enhances the bioremediation of crude oil-polluted marine sandy soil microcosms

A pyrene-degrading consortium OPK containing Mycolicibacterium strains PO1 and PO2, Novosphingobium pentaromativorans PY1 and Bacillus subtilis FW1 effectively biodegraded medium- and long-chain alkanes as well as mixed hydrocarbons in crude oil. The detection of alkB and CYP153 genes in the genome of OPK members supports its phenotypic ability to effectively degrade a broad range of saturated hydrocarbons in crude oil. Zeolite-immobilized OPK was developed as a ready-to-use bioproduct and it exhibited 74% removal of 1000 mg L^-1 crude oil within 96 h in sterilized seawater without nutrient supplementation and maintained high crude oil-removal activity under a broad range of pH values (5.0-9.0), temperatures (30-40 °C) and salinities (20-60‰). In addition, the immobilized OPK retained a high crude oil removal efficacy in semicontinuous experiments and showed reusability for at least 5 cycles. Remarkably, bioaugmentation with zeolite-immobilized OPK in sandy soil microcosms significantly increased crude oil (10,000 mg kg^-1 soil) removal from 45% to 80.67% within 21 days compared to biostimulation and natural attenuation. Moreover, bioaugmentation with exogenous immobilized OPK stimulated an increase in the relative abundances of Alcanivorax genus, indigenous hydrocarbon-degrading bacteria, which in turn enhanced removal efficiency of crude oil contamination from sandy soil microcosms. The results indicate positive interactions between the bioaugmented immobilized consortium, harboring Mycolicibacterium as a key player, and indigenous Alcanivorax, which exhibited crucial functions for improving crude oil removal efficacy. The knowledge obtained forms an important basis for further synthesis and handling of a promising bio-based product for enhancing the in situ bioremediation of crude oil-polluted marine environments.

Biodiversity and oil degradation capacity of oil-degrading bacteria isolated from deep-sea hydrothermal sediments of the South Mid-Atlantic Ridge

Studies have reported that various hydrocarbons and hydrocarbon-degrading bacteria are found in global deep-sea hydrothermal regions. However, little is known about degradation characteristics of culturable hydrocarbon-degrading bacteria from these regions. We speculate that these bacteria can be used as resources for the bioremediation of oil pollution. In this study, six oil-degrading consortia were obtained from the hydrothermal region of the Southern Mid-Atlantic Ridge through room-temperature enrichment experiments. The dominant oil-degrading bacteria belonged to Nitratireductor, Pseudonocardia, Brevundimonas and Acinetobacter. More varieties of hydrocarbon-degrading bacteria were obtained from sediments (preserved at 4 °C) near hydrothermal vents. Most strains had the ability to degrade high molecular weight petroleum components. In addition, Pseudonocardia was shown to exhibit a high degradation ability for phytane and pristine for the first time. This study may provide new insights into the community structure and biodiversity of culturable oil-degrading bacteria in deep-sea hydrothermal regions.

A review on anaerobic microorganisms isolated from oil reservoirs

The Role of microorganisms in the petroleum industry is wide-ranging. To understand the role of microorganisms in hydrocarbon transformation, identification of such microorganisms is vital, especially the ones capable of in situ degradation. Microorganisms play a pivotal role in the degradation of hydrocarbons and remediation of heavy metals. Anaerobic microorganisms such as Sulphate Reducing Bacteria (SRB), responsible for the production of hydrogen sulphide (H₂S) within the reservoir, reduces the oil quality by causing reservoir souring and reduction in oil viscosity. This paper reviews the diversity of SRB, methanogens, Nitrogen Reducing Bacteria (NRB), and fermentative bacteria present in oil reservoirs. It also reviews the extensive diversity of these microorganisms, their applications in petroleum industries, characteristics and adaptability to survive in different conditions, the potential to alter the petroleum hydrocarbons properties, the propensity to petroleum hydrocarbon degradation, and remediation of metals.

Reconstruction and evaluation of oil-degrading consortia isolated from sediments of hydrothermal vents in the South Mid-Atlantic Ridge

In this study, sediments were collected from two different sites in the deep-sea hydrothermal region of the South Atlantic Ocean. Two microbial enrichment cultures (H7S and H11S), which were enriched from the sediments collected at two sample sites, could effectively degrade petroleum hydrocarbons. The bacterial diversity was analyzed by high-throughput sequencing method. The petroleum degradation ability were evaluated by gas chromatography–mass spectrometry and gravimetric analysis. We found that the dominant oil-degrading bacteria of enrichment cultures from the deep-sea hydrothermal area belonged to the genera Pseudomonas, Nitratireductor, Acinetobacter, and Brevundimonas. After a 14-day degradation experiment, the enrichment culture H11S, which was obtained near a hydrothermal vent, exhibited a higher degradation efficiency for alkanes (95%) and polycyclic aromatic hydrocarbons (88%) than the enrichment culture H7S. Interestingly, pristane and phytane as biomarkers were degraded up to 90% and 91% respectively by the enrichment culture H11S, and six culturable oil-degrading bacterial strains were isolated. Acinetobacter junii strain H11S-25, Nitratireductor sp. strain H11S-31 and Pseudomonas sp. strain H11S-28 were used at a density ratio of 95:4:1 to construct high-efficiency oil-degrading consortium H. After a three-day biodegradation experiment, consortium H showed high degradation efficiencies of 74.2% and 65.7% for total alkanes and PAHs, respectively. The degradation efficiency of biomarkers such as pristane and high-molecular-weight polycyclic aromatic hydrocarbons (such as CHR) reached 84.5% and 80.48%, respectively. The findings of this study indicate that the microorganisms in the deep-sea hydrothermal area are potential resources for degrading petroleum hydrocarbons. Consortium H, which was artificially constructed, showed a highly efficient oil-degrading capacity and has significant application prospects in oil pollution bioremediation.

Biodegradation potential assessment by using autochthonous microorganisms from the sediments from Lac Mégantic (Quebec, Canada) contaminated with light residual oil

In July 2013, a fatal train derailment led to an explosion and fire in the town of Lac-Mégantic (LM), Quebec, and the crude oil contamination of regional surface water, soil, and sediment in the adjacent Lake Mégantic. This study investigated the degradation potential of the spilled crude oil by using the sediments from the incident site as the source of microorganisms. Two light crude oils (LM source oil and Alberta Sweet Mixed Blend (ASMB)) were tested at 22 °C for 4 weeks and 4 °C for 8 weeks, respectively. The post-incubation biological and chemical information of the samples were analysed. There was no marked difference in degradation efficacy and biological activities for both the LM and ASMB oils, although the biodegradation potential differed between the two incubations. Higher temperature favoured the growth of microorganisms, thus for the degradation of all petroleum hydrocarbons, except for some conservative biomarkers. The degradation of both oils followed the order of resolved components > total saturated hydrocarbons (TSH) > unresolved complex mixture (UCM) >total aromatic hydrocarbons (TAH). Normal alkanes were generally degraded more significantly than branched ones, and polycyclic aromatic hydrocarbons (PAHs). Degradation of polycyclic aromatic hydrocarbons (PAHs) and their alkylated congeners (APAHs) for both incubations generally decreased as the number of aromatic rings, and the degree of alkylation increased. This study showed that the LM sediments can biodegrade the petroleum hydrocarbons efficaciously if appropriate ambient temperatures are generated to favour the growth of autochthonous microorganisms.

Quantitative evaluation of in-situ bioremediation of compound pollution of oil and heavy metal in sediments from the Bohai Sea, China

Owing to the semi-enclosed environment of the Bohai Sea, the ecological effects caused by an oil spill would be significant. A typical in- situ bioremediation engineering project for of oil-spilled marine sediments was performed in the Bohai Sea and a quantitative assessment of the ecological restoration was performed. The bioremediation efficiencies of n-alkane and PAHs in the sediment are 32.84 ± 21.66% and 50.42 ± 17.49% after 70 days of bioremediation, and 60.99 ± 10.14% and 68.01 ± 18.60% after 210 days, respectively. After 210 days of bioremediation, the degradation rates of two- to three ring PAHs and four-ring PAHs are 84.44 ± 23.03% and 26.62 ± 43.76%, respectively. In addition, the concentrations of the heavy metals first increased by 6.00% due to oil spill degradation and release, and then decreased by 72.60% with the degradation of oil caused by bioremediation or vertical migration. According to the continuous tracking monitoring, the composition of the microbial community in the restored area was similar to that in the control area and the clean area in Bohai Sea after 210 days of bioremediation. These results may provide some theoretical and scientific data to understand the degradation mechanism and assessing the ecological remediation efficiency for oil spills in open sea areas.

Biosurfactant: A new frontier for greener technology and environmental sustainability

Petroleum hydrocarbons, oil, heavy metals pollution is becoming additional severe problem due to the growing call for crude oil and crude oil products related products in several fields of application. Such pollution have fascinated much considerations and attractions as it leads to ecological damages in both marines, aquatic and terrestrial ecosystems. Thus, different techniques including chemical surfactants and complex technologies have been proposed for their clean up from the environment, which in turn has detrimental effects on the environment. As of late, biosurfactant compounds have added much deliberation since they are considered as a reasonable option and eco-accommodating materials for remediation technology. The present society is confronting a few difficulties of usage, authorizing ecological protection and environmental change for the next generations. Biosurfactants hold the special property of minimizing and reducing the interfacial tension of liquids. Such features endure biosurfactants to afford a major part in emulsification, de-emulsification, biodegradability, foam formation, washing performance, surface activity, and detergent formulation, which have potential applications in the diverse industrial set-up. Conversations on cost-effective technologies, renewable materials, novel synthesis, downstream, upstream, emerging characterization techniques, molecular, and genetical engineering are substantial to produce biosurfactant of quality and quantity. Therefore, greater attention is being paid to biosurfactant production by identifying their environmental, and biotechnological applications. Be that as it may, the extravagant cost drew in with biosurfactants biotechnological synthesis and recovery can hamper their application in those areas. Notwithstanding these costs, biosurfactants can be used as these parts shows outstandingly high benefits that can at present beat the expenses incurred in the initial purification and downstream processes. Biosurfactant production by microorganisms is relatively considered one of the crucial know-how for improvement, growth, advancement, and environmental sustainability of the 21st century. There is a developing conversation around environmental safety and the significant role that biosurfactants will progressively play soon, for instance, the use of renewable by-products as substrates, potential reduction, re-use and recycling of waste and waste products. The review confers the usefulness of biosurfactants in the removal of environmental contaminants and, consequently, expanding environmental safety and drive towards greener technology.

Potential of mercury-tolerant bacteria for bio-uptake of mercury leached from discarded fluorescent lamps

In this study, ten bacterial strains were found to be mercury resistant after their isolation from Qatari coastal sediments. Tolerance was found to be up to 100-150 ppm for five strains. Those strains had optimum growth conditions at salinity level of 10 ppm NaCl and pH 7-8. Starting from a concentration 7.9 ppm of mercury extracted from fluorescent lamps and after 6 days of incubation at 37 °C, two isolated strains HA6 (Bacillus spp.) and HA9 (Acinetobacter sp.) showed 96.7% and 98.9% of mercury bio-uptake efficiency, respectively. Other strains were capable of removing more than 60% of extracted mercury.