A tropical soil Actinomycete, Gordonia amicalis HS-11, has been previously demonstrated to degrade unsaturated and saturated hydrocarbons (squalene and n-hexadecane, respectively) in an effective manner. In present study, G. amicalis HS-11 degraded 92.85 ± 3.42% of the provided diesel oil [1% (v/v)] after 16 days of aerobic incubation. The effect of different culture conditions such as carbon source, nitrogen source, pH, temperature, and aeration on degradation was studied. During degradation, this Actinomycete synthesized surface active compounds (SACs) in an extracellular manner that brought about a reduction in surface tension from 69 ± 2.1 to 30 ± 1.1 mN m⁻¹ after 16 days. The morphology of cells grown on diesel was monitored by using a Field Emission Scanning Electron Microscope. Diesel-grown cells were longer and clumped with smooth surfaces, possibly due to the secretion of SACs. The interaction between the cells and diesel oil was studied by Confocal Laser Scanning Microscope. Some cells were adherent on small diesel droplets and others were present in the non-attached form thus confirming the emulsification ability of this organism. The fatty acid profiles of the organism grown on diesel oil for 48 h were different from those on Luria Bertani Broth. The genotoxicity and cytotoxicity of diesel oil before and after degradation were determined. Cytogenetic parameters such as mitotic index (MI); mitosis distribution and chromosomal aberration (type and frequency) were assessed. Oxidative stress was evaluated by measuring levels of catalase, superoxide dismutase and concentration of malondialdehyde. On the basis of these studies it was deduced that the degradation metabolites were relatively non-toxic.

Bioremediation of real-time petroleum refining industry oily waste (PRIOW) is a major challenge due to the poor emulsification potential and oil sludge disintegration efficiency of conventional bioamphiphile molecules. The present study was focused on the design of a covalently engineered supramolecular bioamphiphile complex (SUBC) rich in hydrophobic amino acids for proficient emulsification of hydrocarbons followed by the concomitant degradation of total petroleum hydrocarbons (TPH) in PRIOW using the hydrocarbonoclastic microbial bio-formulation system. The synthesis of SUBC was carried out by pH regulated microbial biosynthesis process and the yield was obtained to be 450.8 mg/g of petroleum oil sludge. The FT-IR and XPS analyses of SUBC revealed the anchoring of hydrophilic moieties of monomeric bioamphiphilic molecules, resulting in the formation of SUBC via covalent interaction. The SUBC was found to be lipoprotein in nature. The maximum loading capacity of SUBC onto surface modified rice hull (SMRH) was achieved to be 45.25 mg/g SMRH at the optimized conditions using RSM-CCD design. The SUBC anchored SMRH was confirmed using SEM, FT-IR, XRD and TGA analyses. The adsorption isotherm models of SUBC onto SMRH were performed. The integrated approach of SUBC-SMRH and hydrocarbonoclastic microbial bio-formulation system, emulsified oil from PRIOW by 92.86 ± 2.26% within 24 h and degraded TPH by 89.25 ± 1.75% within 4 days at the optimum dosage ratio of SUBC-SMRH (0.25 g): PRIOW (1 g): mass of microbial-assisted biocarrier material (0.05 g). The TPH degradation was confirmed by SARA fractional analysis, FT-IR, ¹H NMR and GC-MS analyses. The study suggested that the application of covalently engineered SUBC has resulted in the accelerated degradation of real-time PRIOW in a very short duration without any secondary sludge generation. Thus, the SUBC integrated approach can be considered to effectively manage the hydrocarbon contaminants from petroleum refining industries under optimal conditions.

Biodiesel side stream waste glycerol was identified as a cheap carbon source for rhamnolipids (RLs) production which at the same time could improve the management of waste. The present study aimed to produce RLs by using Pseudomonas aeruginosa RS6 utilizing waste glycerol as a substrate and to evaluate their physico-chemicals properties. Fermentation conditions such as temperature, initial medium pH, waste glycerol concentration, nitrogen sources and concentrations resulted in different compositions of the mono- and di-RLs produced. The maximum RLs production of 2.73 g/L was obtained when P. aeruginosa RS6 was grown in a basal salt medium supplemented with 1% waste glycerol and 0.2 M sodium nitrate at 35 °C and pH 6.5. At optimal fermentation conditions, the emulsification index (E₂₄) values of cooking oil, diesel oil, benzene, olive oil, petroleum, and kerosene were all above E₂₄₌50%. The surface tension reduction obtained from 72.13 mN/m to 29.4–30.4 mN/m was better than the surface activity of some chemical-based surfactants. The RLs produced possessed antimicrobial activities against Gram-negative and Gram-positive bacteria with values ranging from 37% to 77% of growth inhibition when 1 mg/mL of RLs was used. Concentrations of RLs below 1500 μg/mL did not induce phytotoxicity effects on the tested seeds (Vigna radiata) compared to the chemical-based- surfactant, SDS. Furthermore, RLs tested on zebrafish (Danio rerio) embryos only exhibited low acute toxicity with an LC₅₀ value of 72.97 μg/mL at 48 h of exposure suggesting a green and eco-biochemical worthy of future applications to replace chemical-based surfactants.

Crude oil and its derivatives are considered as one group of the most pervasive environmental pollutants in marine environments. Bioremediation using oil-degrading bacteria has emerged as a promising green cleanup alternative in more recent years. The employment of biosurfactant-producing and hydrocarbon-utilizing indigenous bacteria enhances the effectiveness of bioremediation by making hydrocarbons bioavailable for degradation. In this study, the best candidates of biosurfactant-producing indigenous bacteria were selected by screening of biochemical tests. The selected bacteria include Bacillus algicola (003-Phe1), Rhodococcus soli (102-Na5), Isoptericola chiayiensis (103-Na4), and Pseudoalteromonas agarivorans (SDRB-Py1). In general, these isolated species caused low surface tension values (33.9–41.3 mN m−1), high oil spreading (1.2–2.4 cm), and hydrocarbon emulsification (up to 65%) warranting active degradation of hydrocarbons. FT-IR and LC-MS analyses indicated that the monorhamnolipid (Rha-C16:1) and dirhamnolipid (Rha-Rha-C6-C6:1) were commonly produced by the bacteria as potent biosurfactants. The residual crude oil after the biodegradation test was quantitated using GC-MS analysis. The bacteria utilized crude oil as their sole carbon source while the amount of residual crude oil significantly decreased. In addition the cell-free broth containing biosurfactants produced by bacterial strains significantly desorbed crude oil in oil-polluted marine sediment. The selected bacteria might hold additional capacity in crude oil degradation. Biosurfactant-producing indigenous bacteria therefore degrade crude oil hydrocarbon compounds, produce biosurfactants that can increase the emulsification of crude oil and are thus more conducive to the degradation of crude oil.

This paper describes details of an oil spill model, OILTRANS, developed by the authors. The model is an off-line particle-transport model coupled to the most up to date operational met-ocean model forecasts. Formulations for the dominant oil fate processes of spreading, advection, diffusion, evaporation, emulsification and dispersion have been encoded, providing the model with the ability to accurately predict the horizontal movement of surface oil slick, the vertical entrainment of oil into the water column and the mass balance of spilled oil. The application of the OILTRANS model to an accidental release during a ship-to-ship fuel transfer in the Celtic Sea in February 2009 is presented to validate the system. Comparisons with aerial observations of the oil slick at the time of the incident, and subsequent model simulations, indicate that the OILTRANS model is capable of accurately predicting the transport and fate of the oil slick.

Twenty-five crude-oil-degrading bacteria were isolated from oil-contaminated sites in the Persian Gulf and the Caspian Sea. Based on a high growth rate on crude oil and on hydrocarbon degradation ability, 11 strains were selected from the 25 isolated strains for further study. Determination of the nucleotide sequence of the 16S rRNA gene showed that these isolated strains belonged to genera Acinetobacter, Pseudomonas, Gordonia, Rhodococcus, Cobetia, Halomonas, Alcanivorax, Marinobacter and Microbacterium. Among the 11 isolates, strains BS (Acinetobacter calcoaceticus, 98%) and PG-12 (Alcanivorax dieselolei, 98%) were the most effective in degrading crude oil. Rate of crude-oil degradation of 82% (isolate BS) and 71% (isolate PG-12) were observed after 1week of cultivation in mineral medium. These strains had high emulsification activity and biosurfactant production. GC–MS analysis showed that A. dieselolei PG-12 can degrade different alkanes in crude oil. Screening of the distribution of the alkane hydroxylase gene in 25 isolates in relation to the source of isolation indicated that the group (II) alkane hydroxylase is prevalent in the Caspian Sea, but in the Persian Gulf, the frequency of the group (III) alkane hydroxylase gene is greater than that of the group (II) alkane hydroxylase gene.

Effective emulsification plays an important role in the treatment of marine oil spills. The negative effects of chemical surfactants have necessitated a search for alternative dispersant that are sustainable and environmentally-friendly. To identify alternate dispersants, oil-in-seawater emulsions stabilized by hydrocarbon-degrading bacteria were investigated. After individual immobilization and surface-modification, the hydrocarbon-degrading bacteria, Bacillus cereus S-1, was found to produce a stable oil-in-seawater Pickering emulsion, which was similar to particle emulsifiers. The individual immobilization and surface-modification process improved the surface hydrophobicity and wettability of the bacterial cells, which was responsible for their effective adsorption at the oil–water interface. Through effective emulsification, the biodegradation of oil was remarkably facilitated by these treated bacteria, because of the increased interfacial area. By combining the emulsification and biodegradation, the results of this reported work demonstrated a novel approach for developing environmentally-friendly bioremediation technology in the field of oil treatment.

To assess risks of chemically-dispersed oil to marine organisms, oil concentrations in the water were simulated using a hypothetical spill accident in Tokyo Bay. Simulated oil concentrations were then compared with the short-term no-observed effect concentration (NOEC), 0.01mg/L, obtained through toxicity tests using marine diatoms, amphipod and fish. Area of oil concentrations higher than the NOEC were compared with respect to use and non-use of dispersant. Results of the simulation show relatively faster dispersion near the mouth of the bay compared to its inner sections which is basically related to its stronger water currents. Interestingly, in the inner bay, a large area of chemically-dispersed oil has concentrations higher than the NOEC. It seems emulsifying oil by dispersant increases oil concentrations, which could lead to higher toxicity to aquatic organisms. When stronger winds occur, however, the difference in toxic areas between use and non-use of dispersant is quite small.

A flexible 2D/3D oil spill modeling system addressing the distinct nature of the surface and water column fluids, major oil weathering and improved retention/reposition processes in coastal zones is presented. The system integrates hydrodynamic, transport and oil weathering modules, which can be combined to offer different-complexity descriptions as required by applications across the river-to-ocean continuum. Features include accounting for different composition and reology in the surface and water column mixtures, as well as spreading, evaporation, water-in-oil emulsification, shoreline retention, dispersion and dissolution. The use of unstructured grids provides flexibility and efficiency in handling spills in complex geometries and across scales. The use of high-order Eulerian–Lagrangian methods allows for computational efficiency and for handling key processes in ways consistent with their distinct mathematical nature and time scales. The modeling system is tested through a suite of synthetic, laboratory and realistic-domain benchmarks, which demonstrate robust handling of key processes and of 2D/3D couplings. The application of the modeling system to a spill scenario at the entrance of a port in a coastal lagoon illustrates the power of the approach to represent spills that occur in coastal regions with complex boundaries and bathymetry.

Fifteen crude oil degrading bacteria were isolated from oil contaminated sites in the Persian Gulf at Khorramshahr provenance. These bacteria were screened with two important factors such as growth rate on crude oil and hydrocarbon biodegradation, and then three strains were selected from 15 isolated strains for further study. One strain (PG-Z) that show the best crude oil biodegradation was selected between all isolates. Nucleotides sequencing of the gene encoding for 16S rRNA show that strain PG-Z belong to Corynebacterium variabile genus. This strain was efficient in degrading of crude oil. This strain was capable to degraded 82% of crude-oil after one week incubation in ONR7a medium. The PG-Z strain had high emulsification activity and biosurfactant production between all isolates. GC–MS analysis shows that C. variabile strain PG-Z can degrade different alkanes in crude oil.