Biodegradation of Diesel, Crude Oil, Kerosene and Used Engine Oil by a Newly Isolated Bacillus cereus Strain DRDU1 from an Automobile Engine in Liquid Culture

Bioremediation of copper using indigenous fungi Aspergillus species isolated from an abandoned copper mine soil

Bioremediation of mining soils using metal tolerant fungi is widely considered as a promising cost-effective and ecofriendly approach. This study assessed the copper removal efficiency and bioaccumulation ability of the indigenous species Aspergillus hiratsukae LF1 and Aspergillus terreus LF2 isolated from the soils of an abandoned copper mine in Oman. Nutrient medium containing five different Cu (II) levels (0 - control, 100, 200, 300 and 500 mg/L) was employed for assessing both parameters. The removal efficiency from nutrient medium (100-500 mg Cu per L) ranged from 57% to 21% for A. hiratsukae LF1, and from 69% to 24% for A. terreus LF2. A. hiratsukae LF1 and A. terreus LF2 accumulated a maximum of 4.63 and 5.95 mg Cu/g,espectively, at 500 mg/L of Cu (II) concentration. The compositional analysis of extracellular polymeric substances excreted by both species revealed a hormetic response by A. hiratsukae LF1 at 100 mg/L; whereas increasing media Cu levels induced carbohydrates production in A. terreus LF2. These results hint at the involvement of carbohydrates in the Cu-tolerance mechanism of the latter. Copper accumulation in both species was further demonstrated through scanning electron microscopy and energy dispersive spectrometry. In line with the pertaining literature, our results are somewhat inconclusive concerning whether proteins or carbohydrates play a more pivotal role in copper complexation in both species; yet, FTIR analysis showed the participation of different functional groups in Cu sorption. Overall, although additional research is required to advance the knowledge about both Aspergillus species, our findings suggest that A. terreus LF2 presents greater promise for copper bioremediation due to enhanced tolerance and accumulation capacity.

Characterization of new diesel-degrading bacteria isolated from freshwater sediments

As the result of diesel's extensive production and use as fuel for transportation, pollution with such complex mixtures of hydrocarbons is a major concern worldwide. The present study's focus was to investigate the presence of diesel-degrading bacteria in different Danube Delta freshwater sediments. Ten bacterial strains capable to grow in a minimal medium with diesel as the sole carbon source were isolated and characterized in this study. Based on the phenotypic and molecular characteristics, the ten strains belong to four genera and seven species, such as Pseudomonas (P. aeruginosa, P. nitroreducens, P. resinovorans, P. multiresinivorans), Acinetobacter (A. tandoii), Bacillus (B. marisflavi), and Stenotrophomonas (S. maltophilia). All these bacteria were excellent biosurfactant producers, and they were able to tolerate saturated hydrocarbons, like n-heptane, n-decane, n-pentadecane, and n-hexadecane. The ten strains possess at least one alkane hydroxylase gene in their genome, and they were also able to tolerate and degrade diesel. Higher biodegradation rates of diesel were acquired for the strains from the genera Pseudomonas, Acinetobacter, and Stenotrophomonas, compared with that obtained for the Bacillus strain. Due to their remarkable potential to degrade diesel and produce biosurfactants, the ten isolated bacteria are attractive candidates for bioremediation of diesel-polluted environments.

Kerosene Biodegradation by Highly Efficient Indigenous Bacteria Isolated From Hydrocarbon-Contaminated Sites

Kerosene is widely used in Ethiopia as a household fuel (for lighting and heating), as a solvent in paint and grease, and as a lubricant in glass cutting. It causes environmental pollution and escorts to loss of ecological functioning and health problems. Therefore, this research was designed to isolate, identify, and characterize indigenous kerosene-degrading bacteria that are effective in cleaning ecological units that have been contaminated by kerosene. Soil samples were collected from hydrocarbon-contaminated sites (flower farms, garages, and old-aged asphalt roads) and spread-plated on mineral salt medium (Bushnell Hass Mineral Salts Agar Medium: BHMS), which consists of kerosene as the only carbon source. Seven kerosene-degrading bacterial species were isolated, 2 from flower farms, 3 from garage areas, and 2 from asphalt areas. Three genera from hydrocarbon-contaminated sites were identified, including Pseudomonas, Bacillus, and Acinetobacter using biochemical characterization and the Biolog database. Growth studies in the presence of various concentrations of kerosene (1% and 3% v/v) showed that the bacterial isolates could metabolize kerosene as energy and biomass. Thereby, a gravimetric study was performed on bacterial strains that proliferated well on a BHMS medium with kerosene. Remarkably, bacterial isolates were able to degrade 5% kerosene from 57.2% to 91% in 15 days. Moreover, 2 of the most potent isolates, AUG2 and AUG1, resulted in 85% and 91% kerosene degradation, respectively, when allowed to grow on a medium containing kerosene. In addition, 16S rRNA gene analysis indicated that strain AAUG1 belonged to Bacillus tequilensis, whereas isolate AAUG showed the highest similarity to Bacillus subtilis. Therefore, these indigenous bacterial isolates have the potential to be applied for kerosene removal from hydrocarbon-contaminated sites and the development of remediation approaches.

Slurry phase biodegradation of heavy oily sludge and evidence of asphaltene biotransformation

Oily sludge management is a global environmental concern due to its hazardous nature. Oily sludge obtained from a refinery in India had 19-21% oil content. The oil was highly enriched in the asphaltene fraction. Slurry phase biodegradation of this oily sludge in presence of a 3-membered bacterial consortium was optimized in presence of Triton X-100 to increase the bioavailability of hydrocarbons. Triton X-100 at 4 times the critical micelle concentration (CMC) showed the highest degradation where oil removal of 53.1% was achieved from a 10% sludge slurry over 90 days. GCxGC analysis of n-alkanes present in the oily sludge after the biodegradation study showed an increase in the lower n-alkanes, i.e., dodecane and tridecane over the first 30 days, whereas the higher n-alkanes were removed to a much higher extent. Heptadecane showed the maximum extent of degradation with 94.9% removal in 90 days and an initial degradation rate of 0.079 day^-1. The, maximum rate of degradation was observed for pentacosane (0.083 day^-1) with 93.7% removal in 90 days. The increase in the lower n-alkanes may be attributed to biotic transformation of the asphaltene fraction which was also confirmed through FTIR and pyrolysis GCxGC analysis. Biodegradation was found to cause changes in the pyrolysis product of asphaltenes where four and three-ring pyrolysis products decreased while the one and two-ring pyrolysis products increased. In presence of the consortium asphaltene removal over 90 days was 12% whereas only 0.4% removal was obtained in the abiotic controls.

Isolation and development of a microbial consortium for the treatment of automobile service station wastewater

AIM

This work aims to investigate the nature of waste being generated by automobile service stations (ASS) and to devise a microbial-based formulation for the treatment of ASS wastewater.

METHODS AND RESULTS

Analysis of soil and water samples from the vicinity of different ASS in and around the Pune city region (India) revealed the presence of significant amounts of many heavy metals including zinc (Zn) 13.8-175.44 mg kg^-1 , nickel (Ni) 0.6-5.5 mg kg^-1 and copper (Cu) 8.07-179.2 mg kg^-1 as well as oil and grease (O&G). A consortium, consisting of selected members from the ASS soil bacterial isolates, was formulated. The selection of consortium members was based on their ability to degrade hydrocarbons, tolerate heavy metals, and produce biosurfactant and lipase. The developed microbial consortium was capable of reducing the concentration of Ni, manganese (Mn) and chromium (Cr) by 69.25%, 14.63% and 84.93%, respectively, and O&G by 71.8% in the aqueous medium under laboratory conditions.

CONCLUSIONS

Wastewater and soil analysis confirmed the presence of a high amount of O&G and metals in and around ASS. The developed microbial consortium holds potential for the treatment of wastewater rich in O&G and heavy metals.

SIGNIFICANCE AND IMPACT OF THE STUDY

There is a dearth of scientific studies in India on the wastewater and polluted soils associated with ASS. This work reveals and confirms the hazardous nature of ASS and the need for the development and feasibility of microbial-based technology for the sustainable bioremediation of such sites.

Biodegradation of petroleum by bacteria isolated from fishes of Indian Ocean

In this study, oil degrading bacteria discovered from fish living near the oil ports at Karachi in Pakistan were characterized. The bacteria isolated from skin, gills, and gut in fish could consume crude oil as a source of carbon and energy. Total 36 isolates were tested using Nutrient Agar (NA) and MSA media with different crude oil concentrations (0.2%, 0.5%, 0.7%, 1%, 2%, and 5%) and 4 out of 36 isolates (two Gram positive and two Gram negative bacteria) were selected for further identification. 16S rRNA gene sequencing revealed that the isolates are related to Bacillus velezensis, Bacillus flexus, Pseudomonas brenneri and Pseudomonas azotoforman. Oil degrading potential of these bacteria was characterized by GC-MS analysis of degradation of oil components in crude oil as well as engine oil. We found that one (2, 6, 10, 14-Tetramethylpentadecane) out of 42 components in the crude oil was fully eliminated and the other oil components were reduced. In addition, 26 out of 42 oil components in the engine oil, were fully eliminated and the rest were amended. Taken together, these studies identify that B. velezensis, B. flexus, P. brenneri and P. azotoforman have high oil degrading potential, which may be useful for degradation of oil pollutants and other commercial applications.

Biosurfactant mediated bioelectrokinetic remediation of diesel contaminated environment

The present study integrated the electrokinetic (EK) with bioremediation (Bioelectrokinetic -BEK) of diesel hydrocarbon by Staphylococcus epidermidis EVR4. It was identified as efficient biosurfactant producing bacteria and growth parameters was optimized using response surface methodology. Upon degradation, there is a complete disappearance of peaks from nonane (C₉) to tricosane (C₂₃) and 85%, 47% of degradation of pentacosane and octacosane respectively. Marine bacterial strain, EVR4 was found to be potential to degrade the diesel with a maximum degradation efficiency of 96% within 4 d, which was due to its synergistic role of biosurfactant and catabolic enzymes (dehydrogenase, catalase and cytochrome C). The application of integrated BEK was an effective insitu method for the remediation of diesel contaminated soil by BEK (84%) than EK (67%). EVR4 as an effective strain can be employed for BIO-EK method to clean the diesel hydrocarbon polluted environment.

Biodegradation of hydrocarbons by microbial strains in the presence of Ni and Pb

Microbial strains capable of degrading petroleum hydrocarbons were isolated from the Yellow River Delta and screened for bio-surfactant production. The bio-surfactant-producing characteristics of the isolates were evaluated, and all the isolates which could produce bio-surfactant were identified by 16S rRNA gene sequencing. The results showed that the isolates belong to Bacillus sp. (72%), Ochrobactrum sp. (0.16%), Brevundimonas sp. (0.06%) and Brevibacterium sp. (0.06%). The biodegradability of crude oil, gasoline, diesel oil and other hydrocarbons by microbial strains were studied, among which the biodegrading ability of strain P1 and strain P19 is higher than other strains. Both strains P1 and P19 can degrade n-hexane and n-hexadecane effectively and have wide substrate extensiveness. In addition, Ni promoted the biodegradability of toluene by both strain P1 and strain P19, while Pb inhibited the growth of strain P19 and decreased its ability to biodegrade toluene. The studies revealed that microbes including strain P1 and strain P19 can be utilized in bioremediation of co-contaminated water with petroleum and heavy metals including Ni and Pb.

Biodegradation of Petroleum Hydrocarbons by Bacillus subtilis BL-27, a Strain with Weak Hydrophobicity

The biodegradation of petroleum hydrocarbons has many potential applications and has attracted much attention recently. The hydrocarbon-degrading bacterium BL-27 was isolated from petroleum-polluted soil and was compounded with surfactants to improve biodegradation. Its 16S rDNA and rpoD gene sequences indicated that it was a strain of Bacillus subtilis. Strain BL-27 had extensive adaptability and degradability within a broad range of temperatures (25–50 °C), pH (4.0–10.0) and salinity (0–50 g/L NaCl). Under optimal conditions (45 °C, pH 7.0, 1% NaCl), the strain was able to degrade 65% of crude oil (0.3%, w/v) within 5 days using GC-MS analysis. Notably, strain BL-27 had weak cell surface hydrophobicity. The adherence rate of BL-27 to n-hexadecane was 29.6% with sucrose as carbon source and slightly increased to 33.5% with diesel oil (0.3%, w/v) as the sole carbon source, indicating that the cell surface of BL-27 is relatively hydrophilic. The strain was tolerant to SDS, Tween 80, surfactin, and rhamnolipids at a concentration of 500 mg/L. The cell surface hydrophobicity reduced more with the addition of surfactants, while the chemical dispersants, SDS (50–100 mg/L) and Tween 80 (200–500 mg/L), significantly increased the strain’s ability to biodegrade, reaching 75–80%. These results indicated that BL-27 has the potential to be used for the bioremediation of hydrocarbon pollutants and could have promising applications in the petrochemical industry.

Biodegradation of Diesel, Crude Oil and Spent Lubricating Oil by Soil Isolates of Bacillus spp

Two species of Bacillus, B. thuringiensis B3 and B. cereus B6, isolated from crude oil-contaminated sites in Ecuador, were tested for their capability in degrading polycyclic aromatic hydrocarbons (PAHs) in diesel (shake-flask), and to remove total petroleum hydrocarbons (TPHs) from crude oil- or spent lubricating oil-polluted soils (plot-scale). TPHs and PAHs were analyzed by Gas chromatography-Flame ionization detector (GC-FID) and High performance liquid chromatography (HPLC), respectively. Degradation percentages of PAHs by strain B6 were in the range of 11-83 after 30 days. A mixed culture of both the strains removed 84% and 28% of TPHs from crude oil- and spent lubricating oil-polluted soils, respectively. Reduction in the abundance of total n-alkane fractions (C₈-C₄₀) of spent lubricating oil was 94%, which was 18% higher than the control. Our results clearly indicate that the selected strains have great potential in degrading petroleum hydrocarbons at both laboratory- and field-scales.

Anoxic biodegradation of petroleum hydrocarbons in saline media using denitrifier biogranules

The total petroleum hydrocarbons (TPH) biodegradation was examined using biogranules at different initial TPH concentration and contact time under anoxic condition in saline media. The circular compact biogranules having the average diameter between 2 and 3mm were composed of a dense population of Bacillus spp. capable of biodegrading TPH under anoxic condition in saline media were formed in first step of the study. The biogranules could biodegrade over 99% of the TPH at initial concentration up to 2g/L at the contact time of 22h under anoxic condition in saline media. The maximum TPH biodegradation rate of 2.6 gTPH/gbiomass.d could be obtained at initial TPH concentration of 10g/L. Accordingly, the anoxic biogranulation is a possible and promising technique for high-rate biodegradation of petroleum hydrocarbons in saline media.

Effect of Biostimulation Using Sewage Sludge, Soybean Meal, and Wheat Straw on Oil Degradation and Bacterial Community Composition in a Contaminated Desert Soil

Waste materials have a strong potential in the bioremediation of oil-contaminated sites, because of their richness in nutrients and their economical feasibility. We used sewage sludge, soybean meal, and wheat straw to biostimulate oil degradation in a heavily contaminated desert soil. While oil degradation was assessed by following the produced CO₂ and by using gas chromatography–mass spectrometry (GC–MS), shifts in bacterial community composition were monitored using illumina MiSeq. The addition of sewage sludge and wheat straw to the desert soil stimulated the respiration activities to reach 3.2–3.4 times higher than in the untreated soil, whereas the addition of soybean meal resulted in an insignificant change in the produced CO₂, given the high respiration activities of the soybean meal alone. GC–MS analysis revealed that the addition of sewage sludge and wheat straw resulted in 1.7–1.8 fold increase in the degraded C₁₄ to C₃₀ alkanes, compared to only 1.3 fold increase in the case of soybean meal addition. The degradation of ≥90% of the C₁₄ to C₃₀ alkanes was measured in the soils treated with sewage sludge and wheat straw. MiSeq sequencing revealed that the majority (76.5–86.4% of total sequences) of acquired sequences from the untreated soil belonged to Alphaproteobacteria, Gammaproteobacteria, and Firmicutes. Multivariate analysis of operational taxonomic units placed the bacterial communities of the soils after the treatments in separate clusters (ANOSIM R = 0.66, P = 0.0001). The most remarkable shift in bacterial communities was in the wheat straw treatment, where 95–98% of the total sequences were affiliated to Bacilli. We conclude that sewage sludge and wheat straw are useful biostimulating agents for the cleanup of oil-contaminated desert soils.