Oil-degrading Bacteria Research Articles

Biodegradation and removal of heavy oil using Pseudomonas sp. and Bacillus spp. isolated from oily sludge and wastewater in Xinjiang Oilfield, China

Environmental pollution arising from massive production of oily sludge is a global concern. Microbial remediation is an emerging strategy for cleaning up oily sludge-contaminated sites, but it is still challenging to apply heavy oil-degrading bacteria across regions. The aim of this study was to ascertain the feasibility of biodegrading and removing heavy oil from oily sludge by the use of bacterial strains isolated from oily sludge and wastewater collected from Xinjiang Oilfield, Northwest China. The application potential of these bacterial strains for bioremediation of oily sludge-contaminated soils was also evaluated. A total of six oil-degrading bacteria were isolated, three of which showed excellent oil displacement activity (clear zone diameter: 20–23 cm). The three strains were tentatively identified as Pseudomonas reidholzensis (SB2), Bacillus megaterium (SB4), and B. tequilensis (WB1). In a single-factor experiment, the addition of co-substrates stimulated bacterial growth performance on oily sludge agar plates, and all strains formed the largest colonies (mean diameter >11 mm) with sucrose and glucose as co-substrates. Bacterial treatment led to effective biodegradation of heavy oil extracted from oily sludge within 30 days. When additional carbon source (glucose) and nitrogen source (yeast extract) were used, the degradation rate of extracted heavy oil by SB2, SB4, and WB1 reached 15.60%, 11.95%, and 18.43%, respectively. In the oil samples treated with SB2 and SB4, there was a noticeable decrease in the relative abundances of alkenes, cycloalkanes, isoalkanes, and aromatics, accompanied by a slight increase in the relative abundance of n-alkanes. The major oil components all decreased in WB1-treated oil samples. Under simulated conditions, 13.63%, 9.57% and 15.61% of heavy oil was removed from modified oily sludge by SB2, SB4, and WB1, respectively. The results demonstrate the potential of Pseudomonas sp. and Bacillus spp. as candidate strains for use in oily sludge bioremediation.

Employing salt-tolerant bacteria Serratia marcescens subsp. SLS for biodegradation of oily kitchen waste

The high oil and salt content of kitchen waste (KW) inhibit bioconversion and humus production. To efficiently degrade oily kitchen waste (OKW), a halotolerant bacterial strain, Serratia marcescens subsp. SLS which could transform various animal fats and vegetable oils, was isolated from KW compost. Its identification, phylogenetic analysis, lipase activity assays, and oil degradation in liquid medium were assessed, and then it was employed to carry out a simulated OKW composting experiment. In liquid medium, the 24 h degradation rate of mixed oils (soybean oil: peanut oil: olive oil: lard = 1:1:1:1, v/v/v/v) was up to 87.37% at 30 °C, pH 7.0, 280 rpm, 2% oil concentration and 3% NaCl concentration. The ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS) method demonstrated that the mechanism of SLS strain metabolizing long-chain triglycerides (TAGs) (C53–C60), especially the biodegradation of TAG (C18:3/C18:3/C18:3) by the strain can reach more than 90%. Degradation of 5, 10, 15% concentrations of total mixed oil were also calculated to be 64.57, 71.25, 67.99% respectively after a simulated composting duration of 15 days. The results suggest that the isolated strain of S. marcescens subsp. SLS is suitable for OKW bioremediation in high NaCl concentration within a reasonably short period of time. The findings introduced a salt-tolerant and oil-degrading bacteria, providing insights into the mechanism of oil biodegradation and offering new avenues of study for OKW compost and oily wastewater treatment.

Chelativorans petroleitrophicus sp. nov., a paraffin oil-degrading bacterium isolated from a mixture of oil-based drill cuttings and paddy soil.

We isolated a paraffin oil-degrading bacterial strain from a mixture of oil-based drill cutting and paddy soil, and characterized the strain using a polyphasic approach. The Gram-positive, aerobic, rod-shaped and non-spore-forming strain (SCAU 2101T) grew optimally at 50 °C, pH 7.0 and 0.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence indicated that the strain represented a distinct clade in the genus Chelativorans, neighbouring Chelativorans intermedius LMG 28482T (97.1 %). The genome size and DNA G+C content of the strain were 3 969 430 bp and 63.1 mol%, respectively. Whole genome based phylogenomic analyses showed that the average nucleotide identity and digital DNA-DNA hybridization values between strain SCAU 2101T and C. intermedius LMG 28482T were 77.5 and 21.2 %, respectively. The major respiratory quinone was Q-10. The dominant fatty acids were C19 : 0 cyclo ω8c (50.6 %), summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c; 22.5 %) and C18 : 0 (13.8 %). The polar lipids of the strain included phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, phosphatidylcholine and diphosphatidylglycerol. Based on the results, strain SCAU 2101T was considered to represent a novel species in the genus Chelativorans, for which the name Chelativorans petroleitrophicus sp. nov. is proposed. The type strain is SCAU 2101T (= CCTCC AB 2021125T=KCTC 92067T).

Role of Pseudomonas fluorescens FSYZ01 on the corrosion behavior of Q235B carbon steel in oilfield produced water.

The corrosion behavior of Q235B carbon steel is investigated in water, LB medium, and oilfield produced water adding Pseudomonas fluorescens FSYZ01. After immersion at 30°C for 13days, the weight loss of carbon steel with this strain decreased by 32.23%, 54.07%, and 78.34%, respectively. X-ray diffraction (XRD) results show that P. fluorescens FSYZ01 inhibited conversion of iron oxides by hindering oxygen from approaching metal surface. Fourier transform infrared (FT-IR) and X-ray photoelectron spectrometer (XPS) results show that specific functional groups and bonds reacted with Fe(II/III) to form a dense and stable chelate-oxide protective layer, thereby inhibiting corrosion. Pyrolysis gas chromatography-mass spectrometer (Py-GCMS) results demonstrate the bacteria degraded C12 to C20 alkanes in oil. The inhibitory mechanism of crude oil-degrading bacteria P. fluorescens FSYZ01 on the carbon steel corrosion was proposed, so as to slow corrosion of oilfield produced water system pipeline and prolong its service life, helping to comprehend the microbial corrosion in the actual environment.

Valorization of Ketapang Leaves (Terminalia Catappa) as Immoblizing Agent for Hydrocarbon-Degrading Bacteria Dried Storage

One of the mitigations in dealing with the problem of waste oil is by using bioremediation techniques. Bioremediation techniques use biological agents that are safe for the environment and more cost-effective. The method commonly developed in bioremediation techniques is the immobilization of bacteria using plant fibers. The plant fiber used is ketapang leaf (Terminalia catappa) because it has physico-chemical properties that can be used in bioremediation. This study aims to analyze the ability of T. catappa as a living medium for bacteria degrading oil waste and analyze the effect of storage of live media for bacteria degrading oil waste. Five bacterial isolates used in this study were Bacillus aquimaris, B. megaterium, B. pumilus, H. trueperi, and R. bacterium. The live media for waste oil-degrading bacteria was made from T. catappa powder. Tests were carried out on storage days 0, 7, and 28. The results showed that T. catappa leaves could be used as a living medium for bacteria that degrade waste oil (bio carrier) in the amount of 19.9%-55.8%.

Surfactant-enhanced bioremediation of petroleum-contaminated soil and microbial community response: A field study

Surfactant-enhanced bioremediation (SEBR) is frequently employed to clean up soil polluted with petroleum hydrocarbons, but few studies have focused on how surfactants affect microbial communities and different fractions of petroleum hydrocarbons, particularly in the field. Here, the surfactants sodium dodecyl benzene sulfonate (SDBS), alpha olefin sulfonate (AOS), Triton X-100 (TX-100), Tween80, and rhamnolipid were combined with the oil-degrading bacterium Pseudomonas sp. SB to remediate oil-contaminated soil in the laboratory. AOS gave the highest removal efficiency (65.1%) of total petroleum hydrocarbons (TPHs). Therefore, AOS was used in a field experiment with Pseudomonas sp. SB and the removal efficiency of TPHs and long-chain hydrocarbons C21–C40 reached 57.4 and 53.0%, respectively, significantly higher than the other treatments. During bioremediation the addition of Pseudomonas sp. SB significantly stimulated the growth of bacterial genera such as Alcanivorax, Luteimonas, Parvibaculum, Stenotrophomonas, and Pseudomonas and AOS further stimulated the growth of Sphingobacterium, Pseudomonas and Alcanivorax. This study validates the feasibility of surfactant-enhanced bioremediation in the field and partly reveals the mechanism of surfactant-enhanced bioremediation from the perspective of changes in different fractions of petroleum and microbial community dynamics.

Biodegradation of Oil by a Newly Isolated Strain Acinetobacter junii WCO-9 and Its Comparative Pan-Genome Analysis.

Waste oil pollution and the treatment of oily waste present a challenge, and the exploitation of microbial resources is a safe and efficient method to resolve these problems. Lipase-producing microorganisms can directly degrade waste oil and promote the degradation of oily waste and, therefore, have very significant research and application value. The isolation of efficient oil-degrading strains is of great practical significance in research into microbial remediation in oil-contaminated environments and for the enrichment of the microbial lipase resource library. In this study, Acinetobacter junii WCO-9, an efficient oil-degrading bacterium, was isolated from an oil-contaminated soil using olive oil as the sole carbon source, and its enzyme activity of ρ-nitrophenyl decanoate (ρ-NPD) decomposition was 3000 U/L. The WCO-9 strain could degrade a variety of edible oils, and its degradation capability was significantly better than that of the control strain, A junii ATCC 17908. Comparative pan-genome and lipid degradation pathway analyses indicated that A. junii isolated from the same environment shared a similar set of core genes and that the species accumulated more specific genes that facilitated resistance to environmental stresses under different environmental conditions. WCO-9 has accumulated a complete set of oil metabolism genes under a long-term oil-contamination environment, and the compact arrangement of abundant lipase and lipase chaperones has further strengthened the ability of the strain to survive in such environments. This is the main reason why WCO-9 is able to degrade oil significantly more effectively than ATCC 17908. In addition, WCO-9 possesses a specific lipase that is not found in homologous strains. In summary, A. junii WCO-9, with a complete triglyceride degradation pathway and the specific lipase gene, has great potential in environmental remediation and lipase for industry.

Bioremediation of heavy oil-contaminated intertidal zones using slow-release nutrients and rhamnolipid biosurfactants

The decontamination of heavy oil from intertidal sediments requires a green and economic approach. Herein, the effect of a combination of natural mineral slow-release nutrients and rhamnolipid biosurfactants on the bioremediation of a heavy oil- contaminated intertidal zone was studied. Slow-release nutrients had a good extended time performance and resisted seawater dilution. The concentrations of total nitrogen and total phosphorus after 100 days of treatment were 680.5 mg/L and 25.4 mg/L, respectively. The combined application of slow-release nutrients with rhamnolipid biosurfactants effectively improved the metabolic activity of indigenous microorganisms and the biodegradation efficiency of heavy oil. The combined application reduced heavy oil by 39.4%, which was 17.0% higher than the natural attenuation. In addition, we found that n-alkanes and polycyclic aromatic hydrocarbons in heavy oil could be reduced simultaneously. Bacterial community analysis showed that slow-release nutrients and rhamnolipid biosurfactants enriched oil-degrading bacteria, enhanced heavy oil biodegradation. Overall, our findings demonstrated that the combination of slow-release nutrients and rhamnolipid biosurfactants is an effective intertidal oil remediation treatment.

Ancient hydrocarbon slicks recorded by a coral atoll in the South China Sea

The intensifying oil slicks exert deleterious effects on coral reefs, hence attracting many investigations on coral's tolerance and resilience to anthropogenic oil pollution. We hypothesize that intense seafloor hydrocarbon seepages in the past could also produce oil slicks and subsequently contaminate coral reefs nearby, which may provide clues on their responses to natural oil contamination. Here, a long coral reef core (NK1) drilled in the isolated Meiji Atoll in the southern South China Sea is analyzed for aliphatic hydrocarbons to test this hypothesis. Two depth intervals, centered at 45–65 m and 95–110 m, corresponding to ages of ca. 0.3–0.6 Ma and 1.3–1.5 Ma, respectively, are characterized by geological-configured hydrocarbons indicative of ancient natural oil pollution. Because the Meiji Atoll stands on a volcanic seamount and in isolation in the sea, we deem that natural oils were incorporated into contemporary coral reefs by surface oil slicks, which were derived from hydrocarbon seepages at the seafloor of the adjacent petroliferous basins. The natural hydrocarbon seepages should result from regional tectonic movements that occurred extensively in the middle and late Pleistocene, likely in association with the arc-continent collision in the Taiwan region since 2 Ma. Albeit the two significant contamination events, it appears that they exerted insignificant disturbances on the growth and development of coral reefs, perhaps protected by certain holobiotic oil-degrading bacteria as indicated by excess production of bacterial branched fatty acids during the events. Our study thus suggests a high resilience of coral reefs to oil pollution under natural conditions, which, of course, does not mean that they would survive readily from the abrupt and intense anthropogenic pollution.

Biodegradation of Used Engine Oil by Pseudomonas sp. Isolated from an Automobile Workshop’s Soil

Environmental pollution caused by used engine oil has been on the increase as a result of accidental or deliberate discharge of the oil. Used engine oil is relatively recalcitrant to biodegradation due to the high concentrations of metals from the wear and tear of engine parts. Several physical and chemical methods were employed for the remediation of used engine oil-contaminated soil, but bioremediation remains the most economical especially in remediating polluted soils. Therefore, this work aimed to isolate and screen efficient used engine oil-degrading bacteria from serval automobile workshops located at Gadau town, Itas Gadau, Bauchi state, Nigeria. Soil samples were collected from three different locations and were used to isolate, and screen used engine oil-degrading bacteria. The best degrader was Pseudomonas sp. with 82% degradation of 1% (v/v) of used engine oil after 5 days of aerobic incubation. The result further indicated that degradation occurs best at 1% (v/v) and no degradation was recorded at 3% (v/v) of used engine oil. Pseudomonas sp. can be employed in the field remediation of used engine oil-contaminated soil.

Long-term patterns of hydrocarbon biodegradation and bacterial community composition in epipelagic and mesopelagic zones of an Arctic fjord

Oil spill attenuation in Arctic marine environments depends on oil-degrading bacteria. However, the seasonally harsh conditions in the Arctic such as nutrient limitations and sub-zero temperatures limit the activity even for bacteria capable of hydrocarbon metabolism at low temperatures. Here, we investigated whether the variance between epipelagic (seasonal temperature and inorganic nutrient variations) and mesopelagic zone (stable environmental conditions) could limit the growth of oil-degrading bacteria and lead to lower oil biodegradation rates in the epipelagic than in the mesopelagic zone. Therefore, we deployed absorbents coated with three oil types in a SW-Greenland fjord system at 10–20 m (epipelagic) and 615–650 m (mesopelagic) water depth for one year. During this period we monitored the development and succession of the bacterial biofilms colonizing the oil films by 16S rRNA gene amplicon quantification and sequencing, and the progression of oil biodegradation by gas chromatography – mass spectrometry oil fingerprinting analysis. The removal of hydrocarbons was significantly different, with several polycyclic aromatic hydrocarbons showing longer half-life times in the epipelagic than in the mesopelagic zone. Bacterial community composition and density (16S rRNA genes/ cm2) significantly differed between the two zones, with total bacteria reaching to log-fold higher densities (16S rRNA genes/cm2) in the mesopelagic than epipelagic oil-coated absorbents. Consequently, the environmental conditions in the epipelagic zone limited oil biodegradation performance by limiting bacterial growth.

Molecular identification and characterization of indigenous bacterial strains isolated from soils around some oil refineries in Iran

One of the main causes of soil pollution is the release of crude oil into the environment. Indigenous microorganisms with the capability of biodegrading hydrocarbon components can be used to improve the efficiency of microbial bioremediation technology. Here, oil-contaminated soils were collected from five oil refineries (Abadan, Isfahan, Tehran, Tabriz and Shiraz) for screening and isolation of geographically adaptive indigenous oil-degrading bacteria. Bacterial colonies from oil-contaminated soil samples were isolated, which were able to grow in a medium containing crude oil, light, and heavy diesel, as a sole carbon source. Twelve strains were isolated, purified, and identified, using the 16S rRNA gene sequencing analysis. The isolates belonged to five species, including Achromobacter spanius, Klebsiella quasipneumoniae, Ochrobactrum intermedium, Citrobacter amalonaticus, Pseudomonas aeruginosa. These bacterial strains were capable of growing in media containing crude oil, light and heavy diesel for 7 to 9 days and had the potential for biosurfactant production. These bacterial strains can be considered as geographically adaptive bacteria, creating preliminary data for further research to utilize their bioremediation potential.

Phytoremediation of crude oil-contaminated sediment using Suaeda heteroptera enhanced by Nereis succinea and oil-degrading bacteria

A 150-day experiment was performed to investigate the stimulatory effect of a promising phytoremediation strategy consisting of Suaeda heteroptera (S. heteroptera), Nereis succinea (N. succinea), and oil-degrading bacteria for cleaning up total petroleum hydrocarbons (TPHs) in spiked sediment. Inoculation with oil-degrading bacteria and/or N. succinea increased plant yield and TPH accumulation in S. heteroptera plants. The highest TPH dissipation (40.5%) was obtained in the combination treatment, i.e., S. heteroptera + oil-degrading bacteria + N. succinea, in which the sediment TPH concentration decreased from an initial value of 3955 to 2355 mg/kg in 150 days. BAF, BCF, and TF confirmed the role of N. succinea and oil-degrading bacteria in the amelioration and translocation of TPHs. In addition, TPH toxicity of S. heteroptera was alleviated by N. succinea and oil-degrading bacteria addition through the reduction of oxidative stress. Therefore, S. heteroptera could be used for cleaning up oil-contaminated sediment, particularly in the presence of oil-degrading bacteria + N. succinea. Field studies on oil-degrading bacteria + N. succinea may provide new insights on the rehabilitation and restoration of sediments contaminated by TPHs.

A novel chitosan-biochar immobilized microorganism strategy to enhance bioremediation of crude oil in soil

The chitosan-biochar composite is a clean and environmentally friendly immobilized microorganisms carrier. In this study, the chitosan-biochar composite as a carrier to immobilize a compound microbial agent contained Pseudomonas aeruginosa and Bacillus licheniformis, and investigated its role in the remediation of oil-contaminated soil. When using 1% (v/v) acetic acid, 3% (m/v) chitosan solution, 0.1% biochar, 4% (v/v) NaOH solution, freeze-drying 6 h, the optimal chitosan-biochar composite material could be obtained. The specific surfacearea of the material increased to 1.725 m2/g and the average pore size also increased from 130.2260 nm to 165.2980 nm after the addition of biochar through the analysis of specific surface area and pore size, which enlarged the contact area of microorganisms and crude oil with the material. SEM showed that the bacterial successfully adhered to the surface and internal of the material. Using FTIR, the results showed that the synthesis of composite carrier material was the covalent combination of –NH2 on chitosan and –COOH on biochar, forming a new chemical bond –NH–CO-. After 60 days of remediation of oil-contaminated soil, the removal rate of crude oil by chitosan-biochar composite immobilized microorganism method was 45.82%, which was 21.26% higher than that of natural remediation. Simultaneously, several oil-degrading bacteria increased at genus level, including Nocardioides (26.79%–33.09%), Bacillus (3.01%–4.10%), Dietzia (1.84%–5.56%), Pseudomonas (0–0.78%), among which Pseudomonas belongs to exogenous bacteria. The results indicated that the chitosan-biochar composite material has high application value in removing crude oil, and further provides a new strategy for bioremediation of oil-contaminated soil.

Microbial Remediation of Crude Oil in Saline Conditions by Oil-Degrading Bacterium Priestia megaterium FDU301.

Salinity greatly affects the microbial degradation process of crude oil; thus, the isolation and identification of halotolerant microbes is essential. Limited studies explored how microbes respond to increased salinity. In this study, an oil-degrading bacterium Priestia megaterium FDU301 was isolated from the Dagang oil field, which can tolerate a salinity of 6%. Compared to the non-saline condition, oil degradation ratios by P. megaterium FDU301 increased by 15.27% and 11.26% in 0.5% and 3.5% salinity media, respectively. Meanwhile, bacteria degraded various components of crude oil more thoroughly in saline environments, especially mid-chain hydrocarbons (C11-C18). Surface tension under salt stress was lower than that in the non-saline medium, indicating that the amount of biosurfactants produced by bacteria was increased. The microbial activity enhanced markedly in response to increased salinity, which was the main factor for the high degradation ability. As a vital component of biofilms, the production of polysaccharides was accelerated with P. megaterium FDU301 inoculation in saline environments. These results indicate that P. megaterium FDU301 has great potential application in oil bioremediation in saline environments.

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.

Biodegradation of petroleum oil using a constructed nonpathogenic and heavy metal-tolerant bacterial consortium isolated from marine sponges

Marine sponges are an attractive source of bacterial strains that are tolerant to and able to degrade toxic compounds. This study reveals the diverse bacterial communities of marine sponges collected from the Thailand coast by using 16S rRNA gene amplicon sequencing. Functional predictions using Tax4Fun2 indicated that the sponge bacterial communities have the potential for crude oil degradation. In this work, two nonpathogenic crude oil-degrading bacteria, Sphingobium naphthae MO2–4 and Bacillus aryabhattai TL01–2, isolated from the sponges Chalinula sp. and Clathria reinwardti, respectively, were selected to construct a bacterial consortium named MOTL. The results showed that the strains MO2–4 and TL01–2 had biosurfactant producing abilities and each had the ability to adhere to hydrocarbons. These strains also demonstrated capacities for surviving in the presence of various heavy metals. Moreover, strain MO2–4 contained genes encoding hydrocarbon-degrading enzymes. Consortium MOTL achieved 64%, 63%, and 51% degradation efficiencies for 2000 mg L−1 crude oil, diesel oil, and fuel oil, respectively, within 7 days and still maintained its degradation capacity when the concentration of petroleum oil increased to 8000 mg L−1. The consortium could degrade phenanthrene, tetradecane and a mixture of phenanthrene and tetradecane, and its degradation efficiencies were more effective than those of the individual strains. Consequently, the consortium MOTL is a promising candidate for the full-scale application of petroleum bioremediation in the presence of heavy metals.

Enhancing the ability of two kinds of oil-degrading bacteria to treat oily sludge by optimising the growth conditions using a response surface methodology.

Biosurfactant are Surfactants produced by certain microorganisms. These biosurfactants increase the biodegradability of insoluble pollutants. In this study, the fermentation products of Pseudomonas stutzeri Lh-42 (PS) and Rhodococcus sp. PR-1 (RD) were studied by Oil spreading method, emulsifying activity and infrared spectrum analysis. It was proved that these fermentation products were biosurfactant. And then the fermentation conditions of PS, RD were optimised by Placket-Burman (PB) design, hill-climbing experiment and response surface methodology (RSM). N source and liquid loading were significant factors in the fermentation of PS, while C source and speed were significant factors in the fermentation of RD. The surface tension was found to be as low as 39.53 ± 0.25 mN/m for the fermentation conditions of PS with an N source of 4.62 ± 0.41 g and a liquid loading of 28.4 ± 0.3%. The surface tension was 40.70 ± 0.47 mN/m for the incubation conditions of RD with a C source of 26.94 ± 0.62 g and a rotational speed of 210 r/min. Finally, the experimental results for the degradation of oily sludge showed that the degradation rate of oily sludge was improved when the fermentation conditions were optimised. The results of the infrared spectroscopy analysis showed that the organic matter content of the oily sludge treated with PS bacteria was significantly reduced after the optimised fermentation. This study provides a theoretical reference for further use of these bacteria to produce biosurfactants to treat organic matter.

Remediation of Petroleum Contaminated Tidal Flat Sediments by Co-bioremediation System

ABSTRACT The remediation effects of oil-degrading bacteria, Nereis succinea and Suaeda heteroptera, on oil-contaminated sediments were studied by laboratory pot experiments under simulated conditions of intertidal zone. Three concentrations of oil-contaminated sediments (I: 500 mg/Kg, II: 1500 mg/Kg, III: 3000 mg/kg) and four bioremediation treatment groups (bacteria group, bacteria-N. succinea group, bacteria-S. heteroptera group, bacteria-N. succinea-S. heteroptera group) were set up, and the oil removal efficiency was measured after 15, 30, 45, 60, and 70 days of the experiment, respectively. The results showed that the percent removals of total petroleum content, linear hydrocarbons, and polycyclic aromatic hydrocarbons (PAHs) of each sediment under all bioremediation treatments were significantly higher than those of the control groups (P < .05). The bacteria – N. succinea – S. heteroptera synergistic model performed best, after 70 days of remediation tests, the percent removals of total petroleum content reached 51.9%, 47.8%, and 40.6% under I, II, and III oil concentration conditions, respectively, indicating the biological disturbance caused by N. succinea and the rhizosphere effect of S. heteroptera can effectively promote the oil removal of the bioremediation system. In addition, the oil degradation speed in each bioremediation combination showed an increasing trend in the began month, peaked during 15–30 d period, and then decreased obviously at 30–70 d in all bioremediation treatments. We also found that the synergistic bioremediation models promoted the removal of petroleum linear hydrocarbons and PAHs, and the percent removals of linear hydrocarbons were negatively related to their carbon chain length, and the removal rates of PAHs decreased significantly as the number of benzene rings increases. The above results demonstrated the feasibility of co-bioremediation technology in the remediation of petroleum contaminated tidal flat sediments.

Comparing the Effects of Diesel Oil Pollution on Forest and Industrial Soil Microbial Community

Introduction: Diesel oil is the most used petroleum product in Iran and other countries. The majority of diesel oil is stored in underground reservoirs and Fuel stations. This product can heavily pollute the adjacent soil. Diesel oil pollution has some ecological effects on soil that disturb the composition and diversity of the microbial community. The present research aimed to investigate the effects of diesel oil pollution on two different types of soil.&#x0D; Materials and Methods: To examine the effects of diesel oil on microbial communities, two different types of soil (industrial and forest types) were collected from Kerman province, Iran. Six microcosms were designed based on three microcosms existing in each type of soil, including unpolluted microcosm, polluted microcosm, and polluted microcosm with nutrients (Nitrogen and Phosphor). Some factors were assayed in each microcosm during 120 days of the experiment. These factors included total heterotrophic bacteria, total diesel oil-degrading bacteria, dehydrogenase enzyme, and diesel oil biodegradation.&#x0D; Results: The quantity of diesel oil-degrading bacteria was significantly lower than heterotrophic bacteria in all soil microcosms. The quantity of diesel oil-degrading bacteria had a decrement pattern until day 60 of the experiment, but after that, these bacteria had an increment pattern. The best dehydrogenase activity between different microcosms was related to polluting microcosms with diesel oil except for farmland soil. The highest biodegradation of diesel oil in all studied soil types belonged to the industrial microcosm (95%). Statistical analysis of the results indicated a significant correlation between the most probable number quantity of heterotrophic bacteria and other assayed factors. Forest soil was significantly different from other soil types.&#x0D; Conclusion: Given the obtained results of the current research, that forest soil is more sensitive to diesel oil pollution, compared to industrial soil. It is, therefore, possible to propose appropriate strategies for the bioremediation of different studied soil types.