Microbial degradation of petroleum hydrocarbons

Rapid capturing of oil-degrading bacteria by engineered attapulgite and their synergistic remediation for oil spill

HYPOTHESIS

High-efficiency dispersion and enhanced biodegradation play important roles in the treatment of oily wastewater. Due to the flaws of chemical surfactants, it is necessary to study the alternative dispersants that are eco-friendly and sustainable. Therefore, applying natural attapulgite (ATP) to coat Brevibacillus parabrevis for dispersion and biodegradation was studied.

EXPERIMENTS

To capture negatively charged bacteria in water, ATP was modified by positively charged Poly (allylamine hydrochloride) (PAH). The capturing capability of Poly (allylamine hydrochloride)-attapulgite (PAH-ATP) particles for bacterial cells, emulsification of PAH-ATP particles and bacteria on oil, toxicity of PAH-ATP to bacteria, biodegradation of oil, etc., were comprehensively investigated.

FINDINGS

PAH-ATP modified bacteria show a highly effective emulsification for oil due to the synergism of PAH-ATP and bacteria. The emulsion stabilized by (PAH-ATP)@bacteria presents small and stable oil droplets in one month, which is benefit for the following biodegradation. Compared with bare bacteria and PAH-ATP, PAH-ATP can capture bacteria to the surface of the oil droplets which can greatly improve the degradation of oil pollution. Importantly, the presence of PAH-ATP does not inhibit the reproduction and activity of bacteria. Treatment of oily wastewater by combining natural nanoparticles and oil-degrading bacteria has the advantages of economy, environmental protection, and sustainability.

A Review on the Treatment of Petroleum Refinery Wastewater Using Advanced Oxidation Processes

The petroleum industry is one of the most rapidly developing industries and is projected to grow faster in the coming years. The recent environmental activities and global requirements for cleaner methods are pushing the petroleum refining industries for the use of green techniques and industrial wastewater treatment. Petroleum industry wastewater contains a broad diversity of contaminants such as petroleum hydrocarbons, oil and grease, phenol, ammonia, sulfides, and other organic composites, etc. All of these compounds within discharged water from the petroleum industry exist in an extremely complicated form, which is unsafe for the environment. Conventional treatment systems treating refinery wastewater have shown major drawbacks including low efficiency, high capital and operating cost, and sensitivity to low biodegradability and toxicity. The advanced oxidation process (AOP) method is one of the methods applied for petroleum refinery wastewater treatment. The objective of this work is to review the current application of AOP technologies in the treatment of petroleum industry wastewater. The petroleum wastewater treatment using AOP methods includes Fenton and photo-Fenton, H2O2/UV, photocatalysis, ozonation, and biological processes. This review reports that the treatment efficiencies strongly depend on the chosen AOP type, the physical and chemical properties of target contaminants, and the operating conditions. It is reported that other mechanisms, as well as hydroxyl radical oxidation, might occur throughout the AOP treatment and donate to the decrease in target contaminants. Mainly, the recent advances in the AOP treatment of petroleum wastewater are discussed. Moreover, the review identifies scientific literature on knowledge gaps, and future research ways are provided to assess the effects of these technologies in the treatment of petroleum wastewater.

Preparation, optimization and reusability of immobilized petroleum-degrading bacteria

In the remediation of marine pollution, it is important to effectively degrade pollutants and reuse petroleum-degrading bacteria. In order to obtain more effective biodegradability and reusability, an immobilized bacteria combination with petroleum-degrading bacteria, sodium alginate (SA) and biochar by adsorption-embedding method was systematically analysed. The results indicated that the immobilized bacteria had good mechanical properties and the degradation rate was 51% when the straw (CS) was 3%, the SA and CaCl₂ were 4.5% and 6%, respectively. Besides, SA-CS-DM-PVA has the highest degradation rate and the lowest broken rate, above 51% and below 6.1% respectively. The optimum dosage of the modified immobilized bacteria was 132, degradation time was 5d, and reuse frequency was 4 times. Moreover, immobilized bacteria characterized by scanning electron microscopy (SEM), results showed that there were more pores on the surface after degradation, and the carrier was exposed. Therefore, the modified immobilized bacteria with good degradability and reusability, have good application prospects in the treatment of marine oil pollution.

Unravelling the process of petroleum hydrocarbon biodegradation in different filter materials of constructed wetlands by stable isotope fractionation and labelling studies

Maintaining and supporting complete biodegradation during remediation of petroleum hydrocarbon contaminated groundwater in constructed wetlands is vital for the final destruction and removal of contaminants. We aimed to compare and gain insight into biodegradation and explore possible limitations in different filter materials (sand, sand amended with biochar, expanded clay). These filters were collected from constructed wetlands after two years of operation and batch experiments were conducted using two stable isotope techniques; (i) carbon isotope labelling of hexadecane and (ii) hydrogen isotope fractionation of decane. Both hydrocarbon compounds hexadecane and decane were biodegraded. The mineralization rate of hexadecane was higher in the sandy filter material (3.6 µg CO2 g-1 day-1) than in the expanded clay (1.0 µg CO2 g-1 day-1). The microbial community of the constructed wetland microcosms was dominated by Gram negative bacteria and fungi and was specific for the different filter materials while hexadecane was primarily anabolized by bacteria. Adsorption / desorption of petroleum hydrocarbons in expanded clay was observed, which might not hinder but delay biodegradation. Very few cases of hydrogen isotope fractionation were recorded in expanded clay and sand & biochar filters during decane biodegradation. In sand filters, decane was biodegraded more slowly and hydrogen isotope fractionation was visible. Still, the range of observed apparent kinetic hydrogen isotope effects (AKIEH = 1.072-1.500) and apparent decane biodegradation rates (k = - 0.017 to - 0.067 day-1) of the sand filter were low. To conclude, low biodegradation rates, small hydrogen isotope fractionation, zero order mineralization kinetics and lack of microbial biomass growth indicated that mass transfer controlled biodegradation.

Sorption and desorption of petroleum hydrocarbons on biodegradable and nondegradable microplastics

Both biodegradable and nondegradable plastics are widely used. However, their interactions with petroleum hydrocarbons (PHs) have not been sufficiently studied. In this study, a type of biodegradable [polylactic acid (PLA)] and five types of nondegradable microplastics [polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC)] were selected to investigate the sorption and desorption mechanisms of PHs. The sorption kinetics of the six types of microplastics followed a pseudo-second-order kinetics model (R² ranged from 0.956 to 0.999) and indicated that chemical sorption dominated the sorption process. The key rate-controlling steps of the sorption of PHs on microplastics were intraparticle diffusion and liquid film diffusion. The sorption capacity of PHs on microplastics followed the order of PA > PE > PS > PET > PLA > PVC. The difference in sorption capacity might be due to the crystallinity, and rubber or glass state of the microplastics. In addition, all types of microplastics exhibited reversible sorption without noticeable desorption hysteresis. No obvious differences were observed in the sorption and desorption of PHs between biodegradable and nondegradable microplastics. Both biodegradable and nondegradable microplastics could sorb/desorb PHs and serve as transportation vectors.

A review on biosurfactants: properties, applications and current developments

Microbial surfactants are a large number of amphipathic biomolecules with a myriad of biomolecule constituents from various microbial sources that have been studied for their surface tension reduction activities. With unique properties, their applications have been increased in different areas including environment, medicine, healthcare, agriculture and industries. The present review aims to study the biochemistry and biosynthesis of biosurfactants exhibiting varying biomolecular structures which are produced by different microbial sources. It also provides details on roles played by biosurfactants in nature as well as their potential applications in various sectors. Basic biomolecule content of all the biosurfactants studied showed presence of carbohydrates, aminoacids, lipids and fattyacids. The data presented here would help in designing, synthesis and application of tailor-made novel biosurfactants. This would pave a way for perspectives of research on biosurfactants to overcome the existing bottlenecks in this field.

Combined microbial degradation of crude oil under alkaline conditions by Acinetobacter baumannii and Talaromyces sp

The purpose of this work was to study the biodegradation of crude oil under alkaline condition by defined co-culture of Acinetobacter baumannii and Talaromyces sp. The n-alkanes in crude oil could be completely degraded by bacteria and fungi with the ratio of 1:1 at pH 9 in 14 d water simulation experiment. Meanwhile, the total degradation rate of crude oil could reach 80%. Fungi had stronger ability to degrade n-alkanes, while bacteria could better degrade other components such as aromatics and branched alkanes. The two strains were both capable of producing a small amount of biosurfactant. High cell viability was the main factor for strains to exert high degradation ability in alkaline environment. It was preliminarily verified that bacteria and fungi rely on the differences of enzyme systems to achieve synergy in the degradation process. These results indicated that the defined co-culture had great potential for bioremediation in alkaline soils.

Biocatalytic remediation of industrial pollutants for environmental sustainability: Research needs and opportunities

An increasing quantum of pollutants from various industrial sector activities represents a severe menace to environmental & ecological balance. Bioremediation is gaining flow globally due to its cost-effective and environment-friendly nature. Understanding biodegradation mechanisms is of high ecological significance. Application of microbial enzymes has been reported as sustainable approach to mitigate the pollution. Immobilized enzyme catalyzed transformations are getting accelerated attention as potential alternatives to physical and chemical methods. The attention is now also focused on developing novel protein engineering strategies and bioreactor design systems to ameliorate overall biocatalysis and waste treatment further. This paper presents and discusses the most advanced and state of the art scientific & technical developments about biocatalytic remediation of industrial pollutants. It also covers various biocatalysts and the associated sustainable technologies to remediate various pollutants from waste streams. Enzyme production and immobilization in bioreactors have also been discussed. This paper also covers challenges and future research directions in this field.

Attenuation of petroleum hydrocarbon fractions using rhizobacterial isolates possessing alkB, C23O, and nahR genes for degradation of n-alkane and aromatics

This work assessed the catabolic versatility of functional genes in hydrocarbon-utilizing bacteria obtained from the rhizosphere of plants harvested in aged polluted soil sites in Ogoni and their attenuation efficacy in a bioremediation study. Rhizosphere soil was enumerated for its hydrocarbon-utilizing bacteria. The bacteria were in-vitro screened and selected through the quantification of their total protein and specific intermediate pathway enzyme (catechol 2,3-dioxygenase) activity in the metabolism of hydrocarbon. Thereafter, agarose gel electrophoresis technique was deployed to profile the genome of the selected strains for catechol 2,3-dioxygenase (C23O), 1,2-alkane monooxygenase (alkB), and naphthalene dioxygenase (nahR). Four rhizobacterial isolates namely Pseudomonas fluorescens (A3), Achromobacter agilis (A4), Bacillus thuringiensis (D2), and Staphylococcus lentus (L1) were selected based on the presence of C23O, alkB, and nahR genes. The gel electrophoresis results showed an approximate molecular weight of 200 bp for alkB, 300 bp for C23O, and 400 bp for nahR. The gas chromatogram for residual total petroleum hydrocarbon (TPH) revealed mineralization of fractions C₈-C₁₇, phytane, C₁₈-C₃₀. TPH for in-vitro bioremediation of crude oil-polluted soil was observed to have an optimal reduction/loss of 97% within the 56th day of the investigation. This study has further revealed that the microbiome of plants pre-exposed to crude oil pollution could serve as a reservoir for mining group of bacterial with broad catabolic potentials for eco-recovery and waste treatment purposes.

Effect of biostimulation and bioaugmentation on hydrocarbon degradation and detoxification of diesel-contaminated soil: a microcosm study

Soil contamination with diesel oil is quite common during processes of transport and storage. Bioremediation is considered a safe, economical, and environmentally friendly approach for contaminated soil treatment. In this context, studies using hydrocarbon bioremediation have focused on total petroleum hydrocarbon (TPH) analysis to assess process effectiveness, while ecotoxicity has been neglected. Thus, this study aimed to select a microbial consortium capable of detoxifying diesel oil and apply this consortium to the bioremediation of soil contaminated with this environmental pollutant through different bioremediation approaches. Gas chromatography (GC-FID) was used to analyze diesel oil degradation, while ecotoxicological bioassays with the bioindicators Artemia sp., Aliivibrio fischeri (Microtox), and Cucumis sativus were used to assess detoxification. After 90 days of bioremediation, we found that the biostimulation and biostimulation/bioaugmentation approaches showed higher rates of diesel oil degradation in relation to natural attenuation (41.9 and 26.7%, respectively). Phytotoxicity increased in the biostimulation and biostimulation/bioaugmentation treatments during the degradation process, whereas in the Microtox test, the toxicity was the same in these treatments as that in the natural attenuation treatment. In both the phytotoxicity and Microtox tests, bioaugmentation treatment showed lower toxicity. However, compared with natural attenuation, this approach did not show satisfactory hydrocarbon degradation. Based on the microcosm experiments results, we conclude that a broader analysis of the success of bioremediation requires the performance of toxicity bioassays.

Succession of microbial communities and synergetic effects during bioremediation of petroleum hydrocarbon-contaminated soil enhanced by chemical oxidation

Biotechnologies integrated with chemical techniques are promising in treating the soils contaminated by petroleum hydrocarbons. Experiments by applying the degrading consortium and the modified Fenton (MF) with the chelator sodium citrate simultaneously were carried out to investigate the effects of the MF reagents on the degradation of total petroleum hydrocarbons (TPHs), changes in enzyme activities and the succession of microbial communities at the 0, 20, 100 and 500 mmol/kg hydrogen peroxide concentration levels. The ratio between hydrogen peroxide, ferrous sulfate and sodium citrate in the MF reagents was 100:1:1. The results indicated that the degradation of TPHs conformed to first-order kinetics and MF treatments increased the total removal rates of TPHs (4.73-24.26%) and activated dehydrogenase and polyphenol oxidase activities. A shift in microbial communities from Proteobacteria to Bacteroidetes was observed during the enhanced bioremediation, and the predominant genus shifted from Pseudomonas with an average relative abundance (ARAs) of 76.61% at the beginning to Sphingobacterium with ARAs of 52.06% at the later stage. The MF reagents at the proper level could simplify the relationship among the community populations, alleviate their competition and strengthen their associations, which would optimize the removal efficiency.

Refinery wastewater treatment via a multistage enhanced biochemical process

Petroleum refinery wastewater (PRWW) that contains recalcitrant components as the major portion of constituents is difficult to treat by conventional biological processes. An effective and economical biological treatment process was established to treat industrial PRWW with an influent COD of over 2500 mg L⁻¹ in this research. This process is mainly composed of internal circulation biological aerated filter (ICBAF), hydrolysis acidfication (HA), two anaerobic–aerobic (A/O) units, a membrane biological reactor (MBR), and ozone-activated carbon (O₃-AC) units. The results showed that, overall, this system removed over 94% of the COD, BOD_5, ammonia nitrogen (NH₄⁺-N) and phosphorus in the influent, with the ICBAF unit accounting for 54.6% of COD removal and 83.6% of BOD₅ removal, and the two A/O units accounting for 33.3% of COD removal and 9.4% of BOD₅ removal. The degradation processes of eight organic pollutants and their removal via treatment were also analyzed. Furthermore, 26 bacteria were identified in this system, with Proteobacteria and Acidobacteria being the most dominant. Ultimately, the treatment process exhibited good performance in degrading complex organic pollutants in the PRWW.

Biodegradation of C20 carbon clusters from Diesel Fuel by Coriolopsis gallica: optimization, metabolic pathway, phytotoxicity

This study is to test the capacity of the white rot fungus Coriolopsis gallica for the biodegradation of Diesel Fuel hydrocarbons (DHs). Using the experimental face centered central composite design (FCCCD), culture conditions of the Diesel-mended medium were optimized to reach 110.43% of DHs removal rate, and l5267.35 U L-1 of laccase production by C. gallica, simultaneously. The optimal combination of the cultural parameters was: Diesel concentration range of 2.95-3.14%, inoculum size of 3%, incubation time of 15 days, Tween 80 concentration of 0.05%, and the ratio glucose/peptone (G/P) range of 10.15-10.27. Further, the degradation ability of C. gallica for Diesel Fuel was evaluated through mycelial pellets uptake and oxidative action of fungal enzymes in the optimized degrading-medium using gas chromatography-mass spectrometry (GC-MS). Cyclosiloxanes and C20 PAHs detected as the major compound in Diesel Fuel (46%) was completely bio-transformed to simple metabolites including, essentially benzoic acid ester (71%), alcohols (1.52%) epoxy alkane (1.07%), carboxylic acids (1.24%) and quinones (0.33%). Germination rate and root elongation, as a rapid phytotoxicity test demonstrated that toxicity of Diesel's PAHs is minimized by fungal treatment.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02769-w.

Effectiveness of a bio-catalytic agent used in the bioremediation of crude oil-polluted seawater

Oil spillage contamination has been one of the most common and challenging problems in marine ecosystems over the years due to frequent petroleum exploitation, washing, and transportation activities. The use of nature-derived surfactants has become an attractive approach to restore the sites affected by oil spillage. Several studies have demonstrated that nutrient addition is an efficient strategy to enhance oil biodegradation since microorganisms can use petroleum hydrocarbons as their carbon and energy source, thus favoring and increasing the hydrocarbons degradation rate. This study aimed to assess the effectiveness of a commercial bio-catalytic agent used in the biological remediation of crude oil-contaminated sites through the qualitative analysis of its properties. The tests applied to this bio-catalyst showed excellent results. For instance, the emulsification (E₂₄) and critical micellar concentration (CMC) assays displayed average values of 74.47% and 40 mg L⁻¹, respectively. A significant reduction of Chemical Oxygen Demand (COD), turbidity, and Total Petroleum Hydrocarbon Content (TPHC) were observed in all the samples with bio-catalytic agent solution and aeration system. The best water quality was achieved by the sample with the highest concentration (10000 ppm) of bio-catalytic agent solution. It displayed a Total Petroleum Hydrocarbon removal efficiency (RTPH) of 81.537% after 30 days of the remediation time.

A comprehensive review on the applications of functionalized chitosan in petroleum industry

The biomaterials have gained the attention for utilization as sustainable alternatives for petroleum-derived products due to the rapid depletion of petroleum resources and environmental issues. Chitosan is an economical, renewable and abundant polysaccharide having unique molecular characteristics. Chitosan is derived by deacetylation of chitin, a natural polysaccharide existing in insects' exoskeleton, outer shells of crustaceans, and some fungi cell walls. Chitosan is widely used in numerous domains like agriculture, food, water treatment, medicine, cosmetics, fisheries, packaging, and chemical industry. This review aims to account for all the efforts made towards chitosan and its derivatives for utilization in the petroleum industry and related processes including exploration, extraction, refining, transporting oil spillages, and wastewater treatment. This review includes a compilation of various chemical modifications of chitosan to enhance the petroleum field's performance and applicability.

Optimization and characterization of rhamnolipid production by Pseudomonas aeruginosa NY3 using waste frying oil as the sole carbon

Yield and cost are two major factors limiting the widespread use of rhamnolipids (RLs). In the present study, waste frying oil (WFO) was used as the sole carbon source to produce environmentally friendly RLs by Pseudomonas aeruginosa NY3. The Plackett-Burman design (PBD) and Box-Behnken design (BBD) methods were used to maximize the production yield of RL. The PBD results showed that the concentrations of NaNO₃ , Na₂ HPO₄ , and trace elements were the key factors affecting the yield of RL. Furthermore, the BBD results showed that at NaNO₃ , Na₂ HPO₄ , and trace elements concentrations were 4.95, 0.66, and 0.64 mL/L, respectively, the average RL yield reached 9.15 ± 0.52 g/L, 1.58-fold higher than that observed before optimization. Fourier transform infrared spectroscopy (FTIR) and liquid chromatography-ion trap-time of flight mass spectrometry (LCMS-IT-TOF) were used to elucidate the diversity of RL congeners. The results showed that, after optimization, the RL congener diversity increased, and the major RL constituent was converted from di-RLs (64.04%) to mono-RLs (60.44%). These results suggested that the concentrations of the components contained in the culture medium of P. aeruginosa NY3 influenced not only the yield of RL, but also its congener distribution.

Harnessing the Potential of Native Microbial Communities for Bioremediation of Oil Spills in the Iberian Peninsula NW Coast

Oil spills are among the most catastrophic events to marine ecosystems and current remediation techniques are not suitable for ecological restoration. Bioremediation approaches can take advantage of the activity of microorganisms with biodegradation capacity thus helping to accelerate the recovery of contaminated environments. The use of native microorganisms can increase the bioremediation efficiency since they have higher potential to survive in the natural environment while preventing unpredictable ecological impacts associated with the introduction of non-native organisms. In order to know the geographical scale to which a native bioremediation consortium can be applied, we need to understand the spatial heterogeneity of the natural microbial communities with potential for hydrocarbon degradation. In the present study, we aim to describe the genetic diversity and the potential of native microbial communities to degrade petroleum hydrocarbons, at an early stage of bioremediation, along the NW Iberian Peninsula coast, an area particularly susceptible to oil spills. Seawater samples collected in 47 sites were exposed to crude oil for 2 weeks, in enrichment experiments. Seawater samples collected in situ, and samples collected after the enrichment with crude oil, were characterized for prokaryotic communities by using 16S rRNA gene amplicon sequencing and predictive functional profiling. Results showed a drastic decrease in richness and diversity of microbial communities after the enrichment with crude oil. Enriched microbial communities were mainly dominated by genera known to degrade hydrocarbons, namely Alcanivorax, Pseudomonas, Acinetobacter, Rhodococcus, Flavobacterium, Oleibacter, Marinobacter, and Thalassospira, without significant differences between geographic areas and locations. Predictive functional profiling of the enriched microbial consortia showed a high potential to degrade the aromatic compounds aminobenzoate, benzoate, chlorocyclohexane, chlorobenzene, ethylbenzene, naphthalene, polycyclic aromatic compounds, styrene, toluene, and xylene. Only a few genera contributed for more than 50% of this genetic potential for aromatic compounds degradation in the enriched communities, namely Alcanivorax, Thalassospira, and Pseudomonas spp. This work is a starting point for the future development of prototype consortia of hydrocarbon-degrading bacteria to mitigate oil spills in the Iberian NW coast.

Bibliometric Analysis of Hydrocarbon Bioremediation in Cold Regions and a Review on Enhanced Soil Bioremediation

Simple Summary

Anthropogenic activities in cold regions require petroleum oils to support various purposes. With the increased demand of petroleum, accidental oil spills are generated during transportation or refuelling processes. Soil is one of the major victims in petroleum pollution, hence studies have been devoted to find solutions to remove these petroleum hydrocarbons. However, the remote and low-temperature conditions in cold regions hindered the implementation of physical and chemical removal treatments. On the other hand, biological treatments in general have been proposed as an innovative approach to attenuate these hydrocarbon pollutants in soils. To understand the relevancy of biological treatments for cold regions specifically, bibliometric analysis has been applied to systematically analyse studies focused on hydrocarbon removal treatment in a biological way. To expedite the understanding of this analysis, we have summarised these biological treatments and suggested other biological applications in the context of cold conditions.

Abstract

The increased usage of petroleum oils in cold regions has led to widespread oil pollutants in soils. The harsh environmental conditions in cold environments allow the persistence of these oil pollutants in soils for more than 20 years, raising adverse threats to the ecosystem. Microbial bioremediation was proposed and employed as a cost-effective tool to remediate petroleum hydrocarbons present in soils without significantly posing harmful side effects. However, the conventional hydrocarbon bioremediation requires a longer time to achieve the clean-up standard due to various environmental factors in cold regions. Recent biotechnological improvements using biostimulation and/or bioaugmentation strategies are reported and implemented to enhance the hydrocarbon removal efficiency under cold conditions. Thus, this review focuses on the enhanced bioremediation for hydrocarbon-polluted soils in cold regions, highlighting in situ and ex situ approaches and few potential enhancements via the exploitation of molecular and microbial technology in response to the cold condition. The bibliometric analysis of the hydrocarbon bioremediation research in cold regions is also presented.

Petroleum sludge polluted soil remediation: Integrated approach involving novel bacterial consortium and nutrient application

Petroleum sludge has been reported as noteworthy hazardous solid waste generated from industrial activities of petroleum sector. Environment friendly and economically sound treatment of petroleum sludge has attracted global attention worldwide and has become a thrust area of research. Petroleum sludge bioremediation is gaining interest of researchers globally to clean pollutants from soil ecosystems. To date of submission of the work there is no literature available reporting comparing five approaches for remediation of agricultural soil polluted with petroleum sludge employing hydrocarbon utilizing bacterial consortium (HUBC). Further studies on toxicity were performed through pot experiments using Vigna radiata. The aim of this research work was to compare capability of five approaches for remediating petroleum sludge polluted agricultural soil by employing soil microcosms. Best results were obtained when simultaneous application of HUBC and nutrients was performed in microcosm. Highest decrease (93.14 ± 1.75%) of petroleum sludge with sufficient count of hydrocarbon utilizers and decreased nutrients in 42 days was reported. Quality improvement of petroleum sludge contaminated agricultural soil after its bioremediation was performed by pot experiments by checking germination of V. radiata seeds. 85.71% germination of seeds in 5 days was noted for treated soil. Thus, HUBC can be applied as a bioremediating consortium to reclaim petroleum sludge polluted soil.

Rhizoremediation of hydrocarbon contaminated soil using Luffa aegyptiaca (Mill) and associated fungi

The potentials of Luffa aegyptiaca and its rhizospheric, non-mycorrhizal fungi in biodegrading and bio-remediating hydrocarbon contaminated soil were investigated in-vitro and in-situ. Biodegradation study was done in two stages: preliminary study using hydrocarbon treated filter paper and in-vitro with Mineral Salt Media (MSM) read on Spectrophotometer at two photo synthetically active wavelengths (530 nm and 620 nm) while rhizoremediation study was done in-situ in contaminated plot of land. Hydrocarbon utilization ability of the fungi and plant were confirmed using total petroleum hydrocarbon (TPH) analysis and gas chromatography mass spectroscopy (GC-MS). Results show differing rates of hydrocarbon utilization by isolated fungi. In-vitro biodegradation study showed that Aspergillus niger, Fusarium solani, Curvularia lunata and Trichoderma harzianum were best in degrading kerosene (78%), diesel (70%), spent engine oil (83%) and crude oil (77%) respectively. Rhizoremediation study using L. aegyptiaca and C. lunata show that remediation was enhanced to 72.15% as against 32.32% and 14% when only the plant or fungus is used respectively. Hydrocarbon accumulation by L. aegyptiaca also decreased in the presence of the fungus. Curvularia lunata is shown in this study to enhance the germination, survival, growth and bioremediation efficiency of L. aegyptiaca in polluted environment.Novelty statement The potentials of Curvularia lunata, a non-mycorrhizal fungi associated with L. aegyptiaca in survival, growth and phytoremediation of petroleum hydrocarbon polluted soil by L. aegyptiaca is highlighted in this study. Luffa aegyptiaca and its associated fungi is shown to bio-remediate petroleum hydrocarbon through phyto-accumulation and rhizosphere effect.

Complete biodegradation of di-n-butyl phthalate (DBP) by a novel Pseudomonas sp. YJB6

Phthalate acid esters (PAEs) are environmentally ubiquitous and have aroused a worldwide concern due to their threats to environment and human health. Di-n-butyl phthalate (DBP) is one of the most frequently observed PAEs in the environment. In this study, a novel bacterium identified as Pseudomonas sp. YJB6 that isolated from PAEs-contaminated soil was determined to have strong DBP-degrading activity. A complete degradation of DBP in 200 mg/L was achieved within 3 days when YJB6 was cultivated at 31.4 °C with an initial inoculation size of 0.6 (OD600) in basic mineral salts liquid medium (MSM), pH 7.6. The degradation curves of DBP (50-2000 mg/L) fitted well the first-order kinetics model, with a half-life (t_1/2) ranging from 0.86 to 1.88 d. The main degradation intermediates were identified as butyl-ethyl phthalate (BEP), mono-butyl phthalate (MBP), phthalic acid (PA) and benzoic acid (BA), indicating a new complex and complete biodegradation pathway presented by YJB6. DBP might be metabolized through de-esterification, β-oxidation, and hydrolysis, followed by entering the Krebs cycle of YJB6 as a final step. Strain YJB6 was successfully immobilized with sodium alginate (SA), polyvinyl alcohol (PVA), and SA-PVA. The immobilization significantly improved the stability and adaptability of the cells thus resulting in high volumetric DBP-degrading rates compared to that of the freely suspended cells. In addition, these immobilized cells can be reused for many cycles with well conserved in DBP-degrading activity. The ideal DBP degrading ability of the free and immobilized YJB6 cells suggests that strain YJB6, especially the SA-PVA+ YJB6 promises great potential to remove hazardous PAEs.

A critical review on energy recovery and non-hazardous disposal of oily sludge from petroleum industry by pyrolysis

This review systematically reports the pyrolysis of oily sludge (OS) from petroleum industry in regards to its dual features of the energy recovery potential and the environmental risks. The petroleum hydrocarbons are the nonbiodegradable fractions in OS that possess hazardous properties, i.e. ignitability and toxicity. Besides, complicated hazardous elements (i.e. N, S and Cl) and heavy metals inherently existing in OS further aggravate the environmental risks. However, the high oil content and heating value of OS contribute to its huge energy resource potential. Considering the energy demand and the environmental pressure, the ultimate purposes of the OS management are to enhance the oil recovery efficiency to minimize the oil content as well as to stabilize the hazardous elements and heavy metals into the solid residue. Among various OS management technologies, pyrolysis is the most suitable approach to reach both targets. In this review paper, the pyrolysis principle, the kinetics and the product distribution in three-phases are discussed firstly. Then the effects of operating parameters of the pyrolysis process on the quality and the application potential of the three-phase products, as well as the hazardous element distribution are discussed. To further solve the dominant concerns, such as the oil content in the solid residue, the pyrolytic oil quality and the migration of hazardous elements and heavy metals, the potentials of the catalytic pyrolysis and the co-pyrolysis with additives are also summarized. Also, the typical pyrolysis reactors are then presented. From the perspective of the energy efficiency and the non-hazardous disposal, the integrated technology combining the pyrolysis and the combustion for the OS management is recommended. Finally, the remaining challenges of OS pyrolysis encountered in the research and the industrial application are discussed and the related outlooks are itemized.

Naphthalene degradation studies using Pseudomonas sp. strain SA3 from Alang-Sosiya ship breaking yard, Gujarat

Polycyclic aromatic hydrocarbons (PAHs) remediation has received considerable attention due to their significant health concern and environmental pollution. However, PAHs contaminated sites also contain indigenous microbes that can potentially degrade naphthalene. Therefore, this study aimed to isolate, characterise and optimise process parameters for efficient naphthalene degradation. A total of 50 naphthalene degrading bacteria were isolated from Alang-Sosiya ship breaking yard, Bhavnagar, Gujarat and screened for their naphthalene degrading capacity. The selected isolate, Pseudomonas sp. strain SA3 was found to degrade 98.74 ± 0.00% naphthalene at a concentration of 500 ppm after 96 h. Further, optimisation of environmental parameters using one factor at a time approach using different inoculum sizes (v/v), pH, salinity, temperature, carbon and nitrogen source greatly accelerated the degradation process attaining 98.6 ± 0.46% naphthalene degradation after 72 h. The optimised parameters for maximum naphthalene degradation were pH 8, 0.1% peptone as nitrogen source, 8% salinity and 1% (v/v) inoculum size.

Bio-electrokinetic remediation of crude oil contaminated soil enhanced by bacterial biosurfactant

The present study evaluating the coupling between bioremediation (BIO) and electrokinetic (EK) remediation of crude oil hydrocarbon by using bio-electrokinetic (BIO-EK) technique. The application of bacterial biosurfactant (BS) may increase the remediation efficiency by increasing the solubility of organic materials. In this work, the potential biosurfactant producing marine bacteria were isolated and identified by 16S rDNA analysis namely Bacillus subtilis AS2, Bacillus licheniformis AS3 and Bacillus velezensis AS4. Biodegradation efficiency of crude oil was found as 88%, 92% and 97% for strain AS2, AS3 and AS4 respectively, with the optimum temperature of 37 °C and pH 7. FTIR confirm the BS belongs to lipopeptide in nature. GCMS reveals that three isolates degraded the lower to higher molecular weight of the crude oil (C₈ to C₂₈) effectively. Results showed that use of BS in electokinetic remediation enhance the biodegradation rate of crude oil contaminated soil about 92% than EK (60%) in 2 days operation. BS enhances the solubilization of hydrocarbon and it leads to the faster electromigration of hydrocarbon to the anodic compartment, which was confirmed by the presence of higher total organic content than the EK. This study proven that the BIO-EK combined with BS can be used to enhance in situ bioremediation of petroleum contaminated soils.

Occurrence of BTEX from petroleum hydrocarbons in surface water, sediment, and biota from Ubeji Creek of Delta State, Nigeria

Petroleum exploration and production activities pose great threat worldwide in the marine environment with numerous occurrences of spills every year. Ubeji Creek in Nigeria suffers environmental pollution attributable to petroleum exploration. The hydrocarbons in petroleum encompass a large number of toxicants such as BTEX, which are frequently discharged into water bodies during spillage. In terms of scope, this study assessed for the first time BTEX levels in surface water, sediment, and biota of the Ubeji Creek. Environmental samples were collected at designated sampling locations along the Ubeji Creek quarterly for 2 years. Water quality was determined in situ, while BTEX levels in water, sediment, and biota were assessed in the laboratory using GC-FID. The physico-chemical characteristics of water were within the acceptable WHO limits with the exception of DO of 3.01 ± 0.25 mg/L. Organic pollution load could have contributed to the depression of DO level below the limit. BTEX of 5.57 ± 0.62 mg/kg in sediment samples was higher than the level in control sample. The BTEX levels in fish, shrimps, pawpaw fruit, pineapple tissue, bitter leaf, and cassava were 0.37 ± 0.05, 0.39 ± 0.01, 0.56 ± 0.02, 1.35 ± 0.04, 0.46 ± 0.06, and 0.22 ± 0.01 mg/kg, respectively. Accumulation of BTEX in this biota can affect their nutritive quality and consequently pose threat to humans who daily consume them.

Bioremediation of Total Petroleum Hydrocarbons (TPH) by Bioaugmentation and Biostimulation in Water with Floating Oil Spill Containment Booms as Bioreactor Basin

A crude oil spill is a common issue during offshore oil drilling, transport and transfer to onshore. Second, the production of petroleum refinery effluent is known to cause pollution due to its toxic effluent discharge. Sea habitats and onshore soil biota are affected by total petroleum hydrocarbons (TPH) as a pollutant in their natural environment. Crude oil pollution in seawater, estuaries and beaches requires an efficient process of cleaning. To remove crude oil pollutants from seawater, various physicochemical and biological treatment methods have been applied worldwide. A biological treatment method using bacteria, fungi and algae has recently gained a lot of attention due to its efficiency and lower cost. This review introduces various studies related to the bioremediation of crude oil, TPH and related petroleum products by bioaugmentation and biostimulation or both together. Bioremediation studies mentioned in this paper can be used for treatment such as emulsified residual spilled oil in seawater with floating oil spill containment booms as an enclosed basin such as a bioreactor, for petroleum hydrocarbons as a pollutant that will help environmental researchers solve these problems and completely clean-up oil spills in seawater.

Tracking gene expression, metabolic profiles, and biochemical analysis in the halotolerant basidiomycetous yeast Rhodotorula mucilaginosa EXF-1630 during benzo[a]pyrene and phenanthrene biodegradation under hypersaline conditions

Polyaromatic phenanthrene (Phe) and benzo[a]pyrene (BaP) are highly toxic, mutagenic, and carcinogenic contaminants widely dispersed in nature, including saline environments. Polyextremotolerant Rhodotorula mucilaginosa EXF-1630, isolated from Arctic sea ice, was grown on a huge concentration range -10 to 500 ppm- of Phe and BaP as sole carbon sources at hypersaline conditions (1 M NaCl). Selected polycyclic aromatic hydrocarbons (PAHs) supported growth as well as glucose, even at high PAH concentrations. Initially, up to 40% of Phe and BaP were adsorbed, followed by biodegradation, resulting in 80% removal in 10 days. While extracellular laccase, peroxidase, and un-specific peroxygenase activities were not detected, NADPH-cytochrome c reductase activity peaked at 4 days. The successful removal of PAHs and the absence of toxic metabolites were confirmed by toxicological tests on moss Physcomitrium patens, bacterium Aliivibrio fischeri, human erythrocytes, and pulmonary epithelial cells (A549). Metabolic profiles were determined at the midpoint of the biodegradation exponential phase, with added Phe and BaP (100 ppm) and 1 M NaCl. Different hydroxylated products were found in the culture medium, while the conjugative metabolite 1-phenanthryl-β-D-glucopyranose was detected in the medium and in the cells. Transcriptome analysis resulted in 870 upregulated and 2,288 downregulated transcripts on PAHs, in comparison to glucose. Genomic mining of 61 available yeast genomes showed a widespread distribution of 31 xenobiotic degradation pathways in different yeast lineages. Two distributions with similar metabolic capacities included black yeasts and mainly members of the Sporidiobolaceae family (including EXF-1630), respectively. This is the first work describing a metabolic profile and transcriptomic analysis of PAH degradation by yeast.

Effects of organic matter addition on chronically hydrocarbon-contaminated soil

Soil is the recipient of organic pollutants as a consequence of anthropogenic activities. Hydrocarbons are contaminants that pose a risk to human and environmental health. Bioremediation of aging contaminated soils is a challenge due to the low biodegradability of contaminants as a result of their interaction with the soil matrix. The aim of this work was to evaluate the effect of both composting and the addition of mature compost on a soil chronically contaminated with hydrocarbons, focusing mainly on the recovery of soil functions and transformations of the soil matrix as well as microbial community shifts. The initial pollution level was 214 ppm of polycyclic aromatic hydrocarbons (PAHs) and 2500 ppm of aliphatic hydrocarbons (AHs). Composting and compost addition produced changes on soil matrix that promoted the release of PAHs (5.7 and 15 % respectively) but not the net PAH elimination. Interestingly, composting stimulated AHs elimination (about 24 %). The lack of PAHs elimination could be attributed to the insufficient PAHs content to stimulate the microbial degrading capacity, and the preferential consumption of easily absorbed C sources by the bacterial community. Despite the low PAH catabolic potential of the aging soil, metabolic shift was driven by the addition of organic matter, which could be monitored by the ratio of Proteobacteria to Actinobacteria combined with E₄/E₆ ratio. Regarding the quality of the soil, the nutrients provided by the exogenous organic matter contributed to the recovery of the global functions and species diversity of the soil along with the reduction of phytotoxicity.

Diesel in Antarctica and a Bibliometric Study on Its Indigenous Microorganisms as Remediation Agent

Diesel acts as a main energy source to complement human activities in Antarctica. However, the increased expedition in Antarctica has threatened the environment as well as its living organisms. While more efforts on the use of renewable energy are being done, most activities in Antarctica still depend heavily on the use of diesel. Diesel contaminants in their natural state are known to be persistent, complex and toxic. The low temperature in Antarctica worsens these issues, making pollutants more significantly toxic to their environment and indigenous organisms. A bibliometric analysis had demonstrated a gradual increase in the number of studies on the microbial hydrocarbon remediation in Antarctica over the year. It was also found that these studies were dominated by those that used bacteria as remediating agents, whereas very little focus was given on fungi and microalgae. This review presents a summary of the collective and past understanding to the current findings of Antarctic microbial enzymatic degradation of hydrocarbons as well as its genotypic adaptation to the extreme low temperature.

Response of soil bacterial communities to high petroleum content in the absence of remediation procedures

Oil spills are events that frequently lead to petroleum pollution. This pollution may cause stress to microbial communities, which require long adaption periods. Soil petroleum pollution is currently considered one of the most serious environmental problems. In the present work, processes occurring in the bacterial communities of three soil samples with different physicochemical characteristics, artificially polluted with 12% of crude oil, were investigated in 120-day laboratory experiment. It was found that the total petroleum hydrocarbon content did not decrease during this time; however, the proportion of petroleum fractions was altered. Petroleum pollution led to a short-term decrease in the bacterial 16S rRNA gene copy number. On the basis of amplicon sequencing analysis, it was concluded that bacterial community successions were similar in the three soils investigated. Thus, the phyla Actinobacteria and Proteobacteria and candidate TM7 phylum (Saccaribacteria) were predominant with relative abundances ranging from 35 to 58%, 25 to 30%, and 15 to 35% in different samples, respectively. The predominant operational taxonomic units (OTUs) after pollution belonged to the genera Rhodococcus and Mycobacterium, families Nocardioidaceae and Sinobacteraceae, and candidate class ТМ7-3. Genes from the alkIII group encoding monoxygenases were the most abundant compared with other catabolic genes from the alkI, alkII, GN-PAH, and GP-PAH groups, and their copy number significantly increased after pollution. The copy numbers of expressed genes involved in the horizontal transfer of catabolic genes, FlgC, TraG, and OmpF, also increased after pollution by 11-33, 16-63, and 11-71 times, respectively. The bacterial community structure after a high level of petroleum pollution changed because of proliferation of the cells that initially were able to decompose hydrocarbons, and in the second place, because proliferation of the cells that received these catabolic genes through horizontal transfer.

Isolation and characterization of a novel hydrocarbonoclastic and biosurfactant producing bacterial strain: Fictibacillus phosphorivorans RP3

In this study, an indigenous novel hydrocarbonoclastic (kerosene and diesel degrading) and biosurfactant producing strain Fictibacillus phosphorivorans RP3 was identified. The characteristics of bacterial strain were ascertained through its unique morphological and biochemical attributes, 16S rRNA sequencing, and phylogenetic analysis. The degradation of hydrocarbons by F. phosphorivorans RP3 was observed at Day 7, Day 10 and Day 14 of the experimental duration. GC-FID chromatograms demonstrated a significant increase in hydrocarbon degradation (%) with progressing days (from 7 to 14). The bacterium exhibited capability to utilize and degrade n-hexadecane (used for primary screening) and petroleum hydrocarbons (kerosene and diesel; by ≥ 90%). With increase in the number of experimentation days, the optical density of the culture medium increased, whereas pH declined (became acidic) for both Kerosene and Diesel. Absence of resistance to routinely used antibiotics makes it an ideal candidate for future field application. The study is, thus, significant in view of toxicological implications of hydrocarbons and their degradation using environmentally safe techniques so as to maintain ecological and human health.

Aerobic composting remediation of petroleum hydrocarbon-contaminated soil. Current and future perspectives

This article provides a comprehensive review on aerobic composting remediation of soil contaminated with total petroleum hydrocarbons (TPHs). The studies reviewed have demonstrated that composting technology can be applied to treat TPH contamination (as high as 380,000 mg kg^-1) in clay, silt, and sandy soils successfully. Most of these studies reported more than 70% removal efficiency, with a maximum of 99%. During the composting process, the bacteria use TPHs as carbon and energy sources, whereas the fungi produce enzymes that can catalyze oxidation reactions of TPHs. The mutualistic and competitive interactions between the bacteria and fungi are believed to sustain a robust biodegradation system. The highest biodegradation rate is observed during the thermophilic phase. However, the presence of a diverse and dynamic microbial community ensures that TPH degradation occurs in the entire composting process. Initial concentration, soil type, soil/compost ratio, aeration rate, moisture content, C/N ratio, pH, and temperature affect the composting process and should be monitored and controlled to ensure successful degradation. Nevertheless, there is insufficient research on optimizing these operational parameters, especially for large-scale composting. Also, toxic and odorous gas emissions during degradation of TPHs, usually unaddressed, can be potential air pollution sources and need further insightful characterization and mitigation/control research.

Bioremediation of oily sludge by solid complex bacterial agent with a combined two-step process

In the present research, a bioremediation process was developed using solid complex bacterial agents (SCBA) through a combined two-step biodegradation process. Four isolated strains showed high efficiency for the degradation of total petroleum hydrocarbons (TPH) and the reduction of COD of the oily sludge, at 96.6% and 92.6%, respectively. The mixed strains together with bran prepared in form of SCBA exhibited improved performance compared to individual strains, all of which had an optimal temperature of around 35 °C. The use of SCBA provided advantages over commonly used liquid media for storage and transportation. The two-step process, consisting of firstly biosurfactant-assisted oil recovery and secondly biodegradation of the remaining TPH with SCBA, demonstrated the capability for treating oily sludge with high TPH content (>10 wt%) and short process period (60 days). The large-scale (5 tons oily sludge) field test, achieving a TPH removal efficiency of 93.8% and COD reduction of 91.5%, respectively, confirmed the feasibility and superiority of the technology for industrial applications.

Application of extracellular polymers on soil communities exposed to oil and nickel contamination

The petrochemical industry is responsible for many accidental releases of pollutants in soil such as hydrocarbons and toxic metals. This co-contamination is responsible for a delay in the degradation of the organic pollution. Many successful technologies to remove these metals apply extracellular polymeric substances (EPS). In this study, we tested the application of an EPS from a Paenibacillus sp. to aid the bioremediation of soils contaminated with crude oil and nickel. We conducted a microcosm experiment to soils containing combinations of oil, nickel, and EPS. The final concentration of oil was evaluated with an infrared spectrometer. Also, we sequenced the metagenomes of the samples in an ion torrent sequencer. The application of EPS did not aid the removal of hydrocarbons with or without the presence of nickel. However, it led to a smaller decrease in the diversity indexes. EPS decreased the abundance of Actinobacteria and increased that of Proteobacteria. The EPS also decreased the connectivity among Actinobacteria in the network analysis. The results indicated that the addition of EPS had a higher effect on the community structure than nickel. Altogether, our results indicate that this approach did not aid the bioremediation of hydrocarbons likely due to its effect in the community structure that affected hydrocarbonoclastic microorganisms.

Sustainability in ElectroKinetic Remediation Processes: A Critical Analysis

In recent years, the development of suitable technologies for the remediation of environmental contaminations has attracted considerable attention. Among these, electrochemical approaches have gained prominence thanks to the many possible applications and their proven effectiveness. This is particularly evident in the case of inorganic/ionic contaminants, which are not subject to natural attenuation (biological degradation) and are difficult to treat adequately with conventional methods. The purpose of this contribution is to present a critical overview of electrokinetic remediation with particular attention on the sustainability of the various applications. The basis of technology will be briefly mentioned, together with the phenomena that occur in the soil and how that will allow its effectiveness. The main critical issues related to this approach will then be presented, highlighting the problems in terms of sustainability, and discussing some possible solutions to reduce the environmental impact and increase the cost-effectiveness and sustainability of this promising technology.

Revealing of Non-Cultivable Bacteria Associated with the Mycelium of Fungi in the Kerosene-Degrading Community Isolated from the Contaminated Jet Fuel

Fuel (especially kerosene) biodamage is a challenge for global industry. In aviation, where kerosene is a widely used type of fuel, its biodeterioration leads to significant damage. Six isolates of micromycetes from the TS-1 aviation kerosene samples were obtained. Their ability to grow on the fuel was studied, and the difference between biodegradation ability was shown. Micromycetes belonged to the Talaromyces, Penicillium, and Aspergillus genera. It was impossible to obtain bacterial isolates associated with their mycelium. However, 16S rRNA metabarcoding and microscopic observations revealed the presence of bacteria in the micromycete isolates. It seems to be that kerosene-degrading fungi were associated with uncultured bacteria. Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes were abundant in the fungal cultures isolated from the TS-1 jet fuel samples. Most genera among these phyla are known as hydrocarbon degraders. Only bacteria-containing micromycete isolates were able to grow on the kerosene. Most likely, kerosene degradation mechanisms are based on synergism of bacteria and fungi.

Effect of natural microbiome and culturable biosurfactants-producing bacterial consortia of freshwater lake on petroleum-hydrocarbon degradation

Freshwater lake ecosystem is a reservior of valuable microbial diversity. It needs to be explored for addressing key environmental issues like petroleum-hydrocarbon contamination. In this work, the microbial communities (pre and post enriched with petroleum-hydrocarbons) from different layers of freshwater lake, i.e. surface water, sediments and deepwater, were explored through metagenomic and culture-dependent approaches. A total of 41 bacterial phyla were retrieved from pre-enriched samples, which were significantly reduced in enriched samples where Proteobacteria were dominant (87% to 100%) followed by Bacteroidetes (7.37%) and Verrucomicrobia (3.06%). The most dominant hydrocarbon-degrading genera were extensively verified as Pseudomonas (48.65%), Acinetobacter (45.38%), Stenotrophomonas (3.16%) and Brevundimonas (2.07%) in surface water (S1WCC); Acinetobacter (62.46%), Aeromonas (10.7%), Sphingobacterium (5.20%) and Pseudomonas (4.23%) in sediment (S2MCC); and Acinetobacter (46.57%), Pseudomonas (13.10%), Comamonas (12.93%), Flavobacterium (12.18%) and Enterobacter (9.62%) in deep water (S4WCC). Additionally, the maximum biodegradation of petroleum-hydrocarbons (i.e. used engine oil or UEO) was achieved by microbiome of S2MCC (67.60 ± 0.08%) followed by S4WCC (59.70 ± 0.12%), whereas only 36.80 ± 0.10% degradation was achieved by S1WCC microbiome. On the other hand, UEO degradation by cultivable biosurfactant-producing single cultures such as Pseudomonas sp. S2WE, Pseudomonas sp. S2WG, Pseudomonas sp. S2MS, Ochrobactrum sp. S1MM and Bacillus nealsonii S2MT showed 31.10 ± 0.08% to 40.50 ± 0.11% biodegradation. Comparatively, the biodegradation efficiency was found higher (i.e. 42.20 ± 0.12% to 56.10 ± 0.12%) in each consortia comprising of two, three, four, and five bacterial cultures. Conclusively, the isolated culturable biosurfactants-producing bacterial consortium of freshwater lake demonstrated >80% contribution in the total petroleum-hydrocarbons degradation by the natural microbiome of the ecosystem.

Rhizoremediation as a green technology for the remediation of petroleum hydrocarbon-contaminated soils

Rhizoremediation is increasingly becoming a green and sustainable alternative to physico-chemical methods for remediation of contaminated environments through the utilization of symbiotic relationship between plants and their associated soil microorganisms in the root zone. The overall efficiency can be enhanced by identifying suitable plant-microbe combinations for specific contaminants and supporting the process with the application of appropriate soil amendments. This approach not only involves promoting the existing activity of plants and soil microbes, but also introduces an adequate number of microorganisms with specific catabolic activity. Here, we reviewed recent literature on the main mechanisms and key factors in the rhizoremediation process with a particular focus on soils contaminated with total petroleum hydrocarbon (TPH). We then discuss the potential of different soil amendments to accelerate the remediation efficiency based on biostimulation and bioaugmentation processes. Notwithstanding some successes in well-controlled environments, rhizoremediation of TPH under field conditions is still not widespread and considered less attractive than physico-chemical methods. We catalogued the major pitfalls of this remediation approach at the field scale in TPH-contaminated sites and, provide some applicable situations for the future successful use of in situ rhizoremediation of TPH-contaminated soils.

Biosurfactant production from newly isolated Rhodotorula sp.YBR and its great potential in enhanced removal of hydrocarbons from contaminated soils

One of the very promising methods in the field of bioremediation of hydrocarbons is the application of biosurfactant- producing microorganisms based on the use of wastewater as renewable substrates of culture media, contributing to the reduction of costs. With this aim, the production, characterization and properties of the yeast strain YBR producing a biosurfactant newly isolated from an oilfield in Algeria, using wastewater from olive oil mills (OOMW) as a substrate for a low-cost and effective production, have been investigated. Screening of biosurfactant production was carried out with different tests, including emulsification index test (E24), drop collapse test, oil spreading technique and measurement of surface tension (ST). The isolated yeast strain was found to be a potent biosurfactant producer with E24 = 69% and a significant reduction in ST from 72 to 35 mN m^-1. The study of the cultural, biochemical, physiological and genetic characteristics of the isolate allowed us to identify it as Rhodotorula sp. strain YBR. Fermentation was carried out in a 2.5 L Minifors Bioreactor using crude OOMW as culture medium, the E₂₄ value reached 90% and a reduction of 72 to 35 mN m^-1 in ST. A biosurfactant yield = 10.08 ± 0.38 g L^-1 was recorded. The characterization by semi-purification and thin layer chromatography (TLC) of the crude extract of biosurfactant showed the presence of peptides, carbohydrates and lipids in its structure. The crude biosurfactant exhibited interesting properties such as: low critical micellar concentration (CMC), significant reduction in ST and strong emulsifying activity. In addition, it has shown stability over a wide range of pH (2-12), temperature (4-100 °C) and salinity (1-10%). More interestingly, the produced biosurfactant has proven to be of great potential application in the remobilization of hydrocarbons from polluted soil with a removal rate of greater than 95%.

Toxicity assessment of total petroleum hydrocarbons in aquatic environments using the bioluminescent bacterium Aliivibrio fischeri

Toxicity monitoring of environmental pollutants especially petroleum hydrocarbons as priority pollutants is an important environmental issue. This study addresses a rapid, sensitive and cost effective method for the detection of total petroleum hydrocarbons (TPHs) using Aliivibrio fischeri bioluminescence inhibition bioassay. At the first step, the optimum conditions including time, pH and temperature for growth of A. fischeri were determined. Then, two methods were used to evaluate the toxicity of petroleum compounds. In the first method, short-term (15 min) and long-term (16 h) toxicity assays were performed. In the second method luminescence kinetics of A. fischeri was investigated during 24 h. The results demonstrated the most appropriate time for the bacterial growth occurred 16 h after inoculation and optimum temperature and pH were found 25 °C and 7, respectively. Short-term and long-term toxicity did not indicate any toxicity for various concentrations of TPHs (30, 50, 110, 160, 220 mg/L). Considering the luminescence kinetics of A. fischeri the long-term assay was introduced as 6 h. The half maximal effective concentration (EC₅₀) was achieved 1.77 mg/L of TPHs. It is concluded that the luminescence kinetics of A. fischeri can be a valuable approach for assessing toxicity of TPHs in aquatic environments.

Bio-based rhamnolipids production and recovery from waste streams: Status and perspectives

Bio-based rhamnolipid production from waste streams is gaining momentum nowadays because of increasing market demand, huge range of applications and its economic and environment friendly nature. Rhamnolipid type biosurfactants are produced by microorganisms as secondary metabolites and have been used to reduce surface/interfacial tension between two different phases. Biosurfactants have been reported to be used as an alternative to chemical surfactants. Pseudomonas sp. has been frequently used for production of rhamnolipid. Various wastes can be used in production of rhamnolipid. Rhamnolipids are widely used in various industrial applications. The present review provides information about structure and nature of rhamnolipid, production using different waste materials and scale-up of rhamnolipid production. It also provides comprehensive literature on various industrial applications along with perspectives and challenges in this research area.

Concomitant prediction of environmental fate and toxicity of chemical compounds

The environmental fate of many functional molecules that are produced on a large scale as precursors or as additives to specialty goods (plastics, fibers, construction materials, etc.), let alone those synthesized by the pharmaceutical industry, is generally unknown. Assessing their environmental fate is crucial when taking decisions on the manufacturing, handling, usage, and release of these substances, as is the evaluation of their toxicity in humans and other higher organisms. While this data are often hard to come by, the experimental data already available on the biodegradability and toxicity of many unusual compounds (including genuinely xenobiotic molecules) make it possible to develop machine learning systems to predict these features. As such, we have created a predictor of the "risk" associated with the use and release of any chemical. This new system merges computational methods to predict biodegradability with others that assess biological toxicity. The combined platform, named BiodegPred (https://sysbiol.cnb.csic.es/BiodegPred/), provides an informed prognosis of the chance a given molecule can eventually be catabolized in the biosphere, as well as of its eventual toxicity, all available through a simple web interface. While the platform described does not give much information about specific degradation kinetics or particular biodegradation pathways, BiodegPred has been instrumental in anticipating the probable behavior of a large number of new molecules (e.g. antiviral compounds) for which no biodegradation data previously existed.

Treatment of petroleum refinery sludge by petroleum degrading bacterium Stenotrophomonas pavanii IRB19 as an efficient novel technology

Petroleum hydrocarbons (PHCs) in petroleum refinery sludge (PRS) are the most adverse components because of their toxic nature, which are harmful to human health and the aquatic ecosystem. This study aimed to identify and characterize an indigenous bacterium isolated from PRS of Indian oil corporation ltd. (IOCL), Haldia, India, and evaluate its performance for biodegradation of total petroleum hydrocarbon (TPH) of PRS. The bacterium molecularly characterized as Stenotrophomonas sp. IRB19 by 16S rRNA sequencing and phylogenetic analysis. The strain IRB19 showed a significant ability to utilize four different oils (kerosene, diesel, petrol and hexadecane) in-vitro. IRB19 could able to degrade up to 65 ± 2.4% of TPH in 28 d of incubation. Solvent extraction study showed that PRS contain 180.57 ± 3.44 g kg^-1 of TPH and maltene fraction composed of aliphatic, aromatics and polar components of 52 ± 4, 39 ± 2 and 9 ± 1%, respectively. The TPH degradation best fitted for the Gompertz model and followed the first-order kinetics having the rate constant (k) and half-life period (t _1/2) of 0.036 d^-1 and 19 d, respectively. Results of this study verified the suitability of the novel strain IRB19 for the biodegradation of PHCs.

Simulation of Microbial Response to Accidental Diesel Spills in Basins Containing Brackish Sea Water and Sediment

The brackish Baltic Sea is under diesel oil pollution risk due to heavy ship traffic. The situation is exasperated by densely distributed marinas and a vigorous although seasonal recreational boating. The seasonality and physical environmental variations hamper the monitoring of microbial communities in response to diesel oil spills. Hence, an 8-week simulation experiment was established in metal basins (containing 265 L sea water and 18 kg quartz sand or natural shore sand as the littoral sediment) to study the effect of accidental diesel oil spills on microbial communities. Our results demonstrated that microbial communities in the surface water responded to diesel oil contamination, whereas those in the littoral sediment did not, indicating that diesel oil degradation mainly happened in the water. Diesel oil decreased the abundance of bacteria and fungi, but increased bacterial diversity in the water. Time was the predominant driver of microbial succession, attributable to the adaption strategies of microbes. Bacteria were more sensitive to diesel oil contamination than fungi and archaea. Diesel oil increased relative abundances of bacterial phyla, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Flavobacteriia and Cytophagia, and fungal phylum Ascomycota in the surface water. Overall, this study improves the understanding of the immediate ecological impact of accidental diesel oil contamination, providing insights into risk management at the coastal area.

Multispecies Diesel Fuel Biodegradation and Niche Formation Are Ignited by Pioneer Hydrocarbon-Utilizing Proteobacteria in a Soil Bacterial Consortium

A soil bacterial consortium that was grown on diesel fuel and consisted of more than 10 members from different genera was maintained through repetitive subculturing and was utilized as a practical model to investigate a bacterial community that was continuously exposed to petroleum hydrocarbons. Through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification which supported the linkage of genomic data and functionality, two pioneering genera, Sphingobium and Pseudomonas, whose catabolic capabilities were differentiated, were found to be responsible for the creation of specialized ecological niches that were apparently occupied by other bacterial members for survival within the consortium. Coexisting genera Achromobacter and Cupriavidus maintained their existence in the consortium through metabolic dependencies by utilizing hydrocarbon biotransformation products of pioneer metabolism, which was confirmed through growth tests and identification of biotransformation products of the isolated strains. Pioneering Sphingobium and Pseudomonas spp. utilized relatively water-insoluble hydrocarbon parent compounds and facilitated the development of a consortium community structure that resulted in the creation of niches in response to diesel fuel exposure which were created through the production of more-water-soluble biotransformation products available to cocolonizers. That these and other organisms were still present in the consortium after multiple transfers spanning 15 years provided evidence for these ecological niches. Member survival through occupation of these niches led to robustness of each group within the multispecies bacterial community. Overall, these results contribute to our understanding of the complex ecological relationships that may evolve during prokaryotic hydrocarbon pollutant biodegradation.IMPORTANCE There are few metagenome studies that have explored soil consortia maintained on a complex hydrocarbon substrate after the community interrelationships were formed. A soil bacterial consortium maintained on diesel fuel was utilized as a practical model to investigate bacterial community relationships through metagenomics analyses, consortium member isolation, growth assays, and metabolite identification, which supported the linkage of genomic data and functionality. Two pioneering genera were responsible for the biodegradation of aromatics and alkanes by initiating biotransformation and thereby created specialized niches that were populated by other members. A model that represents these relationships was constructed, which contributes to our understanding of the complex ecological relationships that evolve during prokaryotic hydrocarbon pollutant biodegradation.

Evaluation of aerobic biological process with post-ozonation for treatment of mixed industrial and domestic wastewater for potential reuse in agriculture

Suspended growth biological process (SGBP) with post-ozonation (O₃) was investigated for treatment of simulated complex mixed industrial and domestic wastewater at specific conditions. The SGBP was operated under complete aeration, 30/30-min and 60/30-min on/off aeration cycles and effluent was exposed to ozone at 250 mgO₃/h fixed dose and contact time 1 to 60-min. The SGBP performance was maximum under 60/30-min aeration conditions achieving 92.1, 90.6, 83.3 and 83.8% reduction in COD, BOD₅, TN and PO₄-P respectively. Nitrification (64.1%) was uninhibited even on transition to pulse aeration cycles. The concentrations of diesel oil and methylene blue dye were reduced by 83.6 and 93.5% respectively. Post-ozonation oxidized residual organics up to 19.9%, based on COD measurement, and increased effluent BOD₅ up to 49.5%. The results including the crop growth outcomes indicate that SGBP-O₃ process has great potential to improve the quality of mixed industrial and domestic wastewater considerably for various water reuse applications.

Determination of Total Hydrocarbons in Contaminated Soil with "Thin Layer Sorptive Extraction Coupled with Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy"

Soil analysis using infrared spectroscopy has been proposed as an alternative to conventional soil analysis to detect soil contamination. This study therefore aims to develop an innovative, in situ, rapid, precise, and inexpensive method that is easy to implement in order to assess soil contamination with hydrocarbons. This work describes the development and validation of a new extraction method by thin-layer sorptive extraction and attenuated total reflectance-Fourier transform infrared spectroscopy (TLSE-ATR-FTIR). First, this method allows the preconcentration of thermodesorbed pollutants on a polymer thin film and then, their quantification by ATR-FTIR using a standard addition method. A five factor fractional factorial design was used to identify the most significant factors impacting the analysis. These factors include soil texture, total organic carbon (TOC), humidity, and concentrations of contaminants. The results showed that TOC, nature (clay, sandy, and loamy) of the soil, and the concentration of pollutants can affect the infrared absorbance. The analytical method has been validated by verifying the different performance criteria such as linearity, accuracy, precision, and quantitation limit. The comparison of the results obtained by TLSE-ATR-FTIR to the results of conventional analyses carried out by accredited laboratories confirms that the use of the proposed method can become an effective alternative to the current methods for the determination of the total hydrocarbons in soils.

Degradation of petroleum hydrocarbons by embedding immobilized crude oil degrading bacteria

In this study, the removal effect of free and immobilized bacteria on crude oil was determined. Sodium alginate and polyvinyl alcohol were used as embedding agent, and ramie was modified as an adsorbent to immobilize free bacteria. The conditions for preparing immobilized pellets were optimized using the response surface method, and the best combination was simulated and obtained by Design-Expert 8.0. The best degradation rate of immobilized bacteria was 75.52%. The degradation by free bacteria and immobilized bacteria showed that the selected microorganisms had a good degradation effect on petroleum hydrocarbons.