Total Petroleum Hydrocarbon Degradation Research Articles

Study on the co-catalytic performance and mechanism of MoO2 in oil-contaminated wastewater treated by Fenton system

BackgroundIn the treatment of organic wastewater, Fenton technology often produces iron sludge due to iron circulation obstruction, which inhibits the treatment efficiency and causes secondary pollution to the actual water. MethodsIn this study, MoO2 was used as a cocatalyst to promote the effective cycling of Fe2+/Fe3+ in the Fe2+/H2O2 system, thus efficiently degrading total petroleum hydrocarbons (TPHs). The superiority of MoO2 as co-catalyst was verified under different reaction conditions, and its mechanism was discussed. FindingsThe degradation rate of TPHs in the Fe2+/H2O2/MoO2 system (0.069 min−1) was about 14 times that of Fe2+/H2O2 system (0.005 min−1). Compared with the Fe2+/H2O2 system, the Fe2+/H2O2/MoO2 system not only had a wider pH adaptation range, but also could effectively remove TPHs under the interference of co-existing organic and inorganic anions. MoO2 did not change the types of reactive species in Fenton system, but it enhanced the production of reactive oxygen species (ROS) by promoting the Fe2+/Fe3+ cycling in the reaction system, and ·OH was the main reactive species of TPHs degradation.

Sulfur-containing iron carbon nanocomposites activate persulfate for combined chemical oxidation and microbial remediation of petroleum-polluted soil

In this study, sulfur-containing iron carbon nanocomposites (S@Fe-CN) were synthesized by calcining iron-loaded biomass and utilized to activate persulfate (PS) for the combined chemical oxidation and microbial remediation of petroleum-polluted soil. The highest removal efficiency of total petroleum hydrocarbons (TPHs) was achieved at 0.2% of activator, 1% of PS and 1:1 soil-water ratio. The EPR and quenching experiments demonstrated that the degradation of TPHs was caused by the combination of 1O2,·OH, SO4·-, and O2·-. In the S@Fe-CN activated PS (S@Fe-CN/PS) system, the degradation of TPHs underwent two phases: chemical oxidation (days 0 to 3) and microbial degradation (days 3 to 28), with kinetic constants consistent with the pseudo-first-order kinetics of chemical and microbial remediation, respectively. In the S@Fe-CN/PS system, soil enzyme activities decreased and then increased, indicating that microbial activities were restored after chemical oxidation under the protection of the activators. The microbial community analysis showed that the S@Fe-CN/PS group affected the abundance and structure of microorganisms, with the relative abundance of TPH-degrading bacteria increased after 28 days. Moreover, S@Fe-CN/PS enhanced the microbial interactions and mitigated microbial competition, thereby improving the ability of indigenous microorganisms to degrade TPHs.

POTENTIAL OF MYCORRHIZAL INOCULATION AND CATTLE RUMEN DIGESTA IN THE BIOREMEDIATION OF SPENT ENGINE OIL CONTAMINATED SOIL

Soil pollution by crude oil contamination has become a major constraint on agricultural productivity. Physicochemical techniques are often expensive. However, bioremediation of petroleum hydrocarbon polluted soil is cost-effective. Therefore, the study was carried out to analyze the influence of mycorrhiza and cattle rumen digesta on bioremediation of Spent Engine Oil (SEO) contaminated soil in Dutse, Jigawa state. Soil samples were randomly collected from the University Research and Teaching Farm. About 2.5 kg of sterilized topsoil (0–15 cm) was filled into pots and arranged in a 2×2×3 factorial experiment in completely randomized design with three replications. Mycorrhiza and cattle rumen digesta were at two levels, while SEO was at three levels. Data were collected on the total petroleum hydrocarbon (TPH) content, bacterial and fungal colony count. Data were analyzed using ANOVA at α 0.05. Results obtained from the study show that mycorrhiza and cattle rumen digesta increased the colonies of fungi and bacteria resulting in significantly enhanced TPH degradation in the contaminated soil. However, cattle rumen digesta significantly (p<0.05) enhanced TPH degradation, bacterial and fungal population the most compared to mycorrhiza alone. Combined cattle rumen digesta and mycorrhiza application resulted in significantly (p<0.05) lower residual TPH content in the contaminated soil compared to using cattle rumen digesta or mycorrhiza alone. Thus, cattle rumen digesta and mycorrhiza should be used in bioremediation of petroleum hydrocarbon impacted soils.

Water conditions and arbuscular mycorrhizal symbiosis affect the phytoremediation of petroleum-contaminated soil by Phragmites australis

Phytoremediation of petroleum-contaminated soils using the synergistic functions of plants and rhizosphere microorganisms is a promising technology. However, successfully applying this approach presents challenges under certain conditions (submerged environments). This study analyzed the potential role of Phragmites australis in symbiosis with arbuscular mycorrhizal (AM) fungi during petroleum remediation at two water levels. AM inoculation promoted P. australis aboveground growth under non-flooded conditions, whereas flooding significantly increased P. australis biomass. The highest total petroleum hydrocarbon (TPH) degradation efficiency was observed in non-flooded soils, whereas submergence severely inhibited TPHs dissipation. Plants with AM inoculation treatments substantially enhanced the removal of TPHs under flooded conditions. TPH removal was positively correlated with dehydrogenase activity but negatively correlated with easily extracted glomalin-related soil proteins. Moreover, different petroleum-hydrocarbon-decaying candidates contributed to TPH removal in these two cultured soils. These findings provide valuable information for the remediation of future TPH-contaminated soils, especially applied in intermittently submerged environments.

Unraveling the functional instability of bacterial consortia in crude oil degradation via integrated co-occurrence networks.

Soil ecosystems are threatened by crude oil contamination, requiring effective microbial remediation. However, our understanding of the key microbial taxa within the community, their interactions impacting crude oil degradation, and the stability of microbial functionality in oil degradation remain limited. To better understand these key points, we enriched a crude oil-degrading bacterial consortium generation 1 (G1) from contaminated soil and conducted three successive transfer passages (G2, G3, and G4). Integrated Co-occurrence Networks method was used to analyze microbial species correlation with crude oil components across G1-G4. In this study, G1 achieved a total petroleum hydrocarbon (TPH) degradation rate of 32.29% within 10 days. Through three successive transfer passages, G2-G4 consortia were established, resulting in a gradual decrease in TPH degradation to 23.14% at the same time. Specifically, saturated hydrocarbon degradation rates ranged from 18.32% to 14.17% among G1-G4, and only G1 exhibited significant aromatic hydrocarbon degradation (15.59%). Functional annotation based on PICRUSt2 and FAPROTAX showed that functional potential of hydrocarbons degradation diminished across generations. These results demonstrated the functional instability of the bacterial consortium in crude oil degradation. The relative abundance of the Dietzia genus showed the highest positive correlation with the degradation efficiency of TPH and saturated hydrocarbons (19.48, 18.38, p < 0.05, respectively), Bacillus genus demonstrated the highest positive correlation (21.94, p < 0.05) with the efficiency of aromatic hydrocarbon degradation. The key scores of Dietzia genus decreased in successive generations. A significant positive correlation (16.56, p < 0.05) was observed between the Bacillus and Mycetocola genera exclusively in the G1 generation. The decline in crude oil degradation function during transfers was closely related to changes in the relative abundance of key genera such as Dietzia and Bacillus as well as their interactions with other genera including Mycetocola genus. Our study identified key bacterial genera involved in crude oil remediation microbiome construction, providing a theoretical basis for the next step in the construction of the oil pollution remediation microbiome.

In‐situ remediation of TPH‐polluted soil by Na2FeO4 in the Loess Plateau of China

AbstractIn recent years, the oil pollution problem on the Loess Plateau in western China is becoming increasingly serious, therefore, the use of hydroxyl radical (·OH) advanced oxidation process has increased due to its ability to efficiently degrade total petroleum hydrocarbon (TPH) in soil. However, the ability to produce ·OH of different oxidants varies widely, and the removal effect of specific pollutants has fluctuations and differences. The objective of this study is to screen the best oxidant according to the physico‐chemical properties and pollution situation of polluted soil, and to reveal the degradation mechanism of pollutants. In this study, we employed sodium ferrate (Na2FeO4) to produce ·OH for the degradation of TPHs in aged oil‐polluted soil located in the western part of the Loess Plateau in China. The results showed that the removal rates of TPH in the soil samples by hydrogen peroxide (H2O2), sodium persulfate (Na2SO4) and Na2FeO4 could reach 45.5%, 62.4%, and 65.6% respectively. The ·OH produced during the process played a major role in TPH oxidation with a contribution of more than 80%; H2O2 was intermediate substance that generated ·OH, biochar could induce the production of ·OH, the addition of biochar could activate H2O2 to promote the generation of ·OH and the removal rate is significantly increased by 19.2%. In situ remediation of polluted soil on the Loess Plateau using Na2FeO4, with a TPH degradation rate of 87.5%. The results of this study will provide a new method for the efficient degradation of TPH in loessial soil.

Synergistic effect of process parameters and nanoparticles on spent lubricant oil waste biodegradation by UV-exposed Scenedesmus vacuolatus: Process modelling, kinetics and degradation pathways

The study examines the impact of process parameters and nanoparticles (NPs) on the degradation of spent coolant waste (SCW) by UV-exposed S. vacuolatus. The model was experimentally optimized using response surface methodology (RSM) with high coefficient of determination (R2) >0.99. Upon validation of the model, total petroleum hydrocarbon (TPH) degradation of 100 % was obtained after 15 days under the optimized conditions of 25 °C temperature, 10 % (v/v) substrate concentration and 10 % (v/v) inoculum concentration. Moreover, the sensitivity of the process parameters on the degradation process assessed using artificial neural network (ANN) revealed high sensitivity of the degradation process to operational temperature. Metabolites obtained provide strong evidence for terminal oxidation and subterminal oxidation metabolic pathways in SCW degradation. In addition, the incorporation of NPs in the SCW degradation significantly enhanced the biodegradation efficiency of UV-exposed S. vacuolatus resulting in shortened degradation period from 15 to 12 days. Likewise, the inclusion of NPs substantially improved UV-exposed S. vacuolatus affinity (1/Ks) for SCW, growth constant (Kg) and maximum specific growth rate (μmax). The degradation kinetics followed the second-order reaction with degradation rate constant (K) in the range of 0.029 to 0.288 m−1 t−1 for monoaromatics and 0.972 to 4.130 m−1 t−1 for PAHs, at half-life (T1/2) ranges of 0.75 to 1.52 day−1 and 0.08 to 0.23 day−1, respectively. This knowledge will enhance the design of waste pollutant degradation towards sustainable green environment.

Potential natural attenuation of petroleum hydrocarbons in fuel contaminated soils: Focusing on anaerobic fuel biodegradation involving microbial Fe(III) reduction

Liquid fossil fuels, collectively known as total petroleum hydrocarbons (TPHs), are highly toxic and frequently leak into subsurface environments due to anthropogenic activities. As an in-situ biological remedial option for TPH contamination, aerobic TPH biodegradation is limited due to oxygen's low solubility in water, and because it is consumed quickly by aerobic bacteria. Thus, we investigated the potential of anaerobic TPH degradation by indigenous fermenting bacteria and Fe(III)-reducing bacteria. Twenty 6–10 m soil cores were collected from a closed military base subject to ongoing TPH contamination since the 1980s. Physicochemical and microbial properties were determined at 0.5-m intervals in each core. To assess the relationship between TPH degradation and microbial Fe(III) reduction, soil samples were grouped into high-TPH (>500 mg kg−1) and high-Fe(II) (>450 mg kg−1), high-TPH and low-Fe(II), low-TPH and high-Fe(II), and low-TPH and low-Fe(II) groups. Alpha diversity was significantly lower in high-TPH groups than in low-TPH groups, suggesting that high TPH concentrations exerted a strong selective pressure on bacterial communities. In the high-TPH and low-Fe(II) group, fermenting bacteria, including Microgenomatia and Chlamydiae, were more abundant, suggesting that TPH biodegradation occurred via fermentation. In the high-TPH and high-Fe(II) group, Fe(III)-reducing bacteria, including Geobacter and Zoogloea, were more abundant, suggesting that microbial Fe(III) reduction enhances TPH biodegradation. In contrast, the fermenting and/or Fe(III)-reducing bacteria were not statistically abundant in the low-TPH groups.

A comprehensive study on diesel oil bioremediation under microcosm conditions using a combined microbiological, enzymatic, mass spectrometry, and metabarcoding approach.

This study aims at the application of a marine fungal consortium (Aspergillus sclerotiorum CRM 348 and Cryptococcus laurentii CRM 707) for the bioremediation of diesel oil-contaminated soil under microcosm conditions. The impact of biostimulation (BS) and/or bioaugmentation (BA) treatments on diesel-oil biodegradation, soil quality, and the structure of the microbial community were studied. The use of the fungal consortium together with nutrients (BA/BS) resulted in a TPH (Total Petroleum Hydrocarbon) degradation 42% higher than that obtained by natural attenuation (NA) within 120days. For the same period, a 72 to 92% removal of short-chain alkanes (C12 to C19) was obtained by BA/BS, while only 3 to 65% removal was achieved by NA. BA/BS also showed high degradation efficiency of long-chain alkanes (C20 to C24) at 120 days, reaching 90 and 92% of degradation of icosane and heneicosane, respectively. In contrast, an increase in the levels of cyclosiloxanes (characterized as bacterial bioemulsifiers and biosurfactants) was observed in the soil treated by the consortium. Conversely, the NA presented a maximum of 37% of degradation of these alkane fractions. The 5-ringed PAH benzo(a)pyrene, was removed significantly better with the BA/BS treatment than with the NA (48 vs. 38 % of biodegradation, respectively). Metabarcoding analysis revealed that BA/BS caused a decrease in the soil microbial diversity with a concomitant increase in the abundance of specific microbial groups, including hydrocarbon-degrading (bacteria and fungi) and also an enhancement in soil microbial activity. Our results highlight the great potential of this consortium for soil treatment after diesel spills, as well as the relevance of the massive sequencing, enzymatic, microbiological and GC-HRMS analyses for a better understanding of diesel bioremediation.

Activation behavior of Cu0/FeS/N-graphene derived from waste soybean residue for peroxymonosulfate: Performance and mechanism

Nitrogen-enriched graphene grown on zero valent copper (Cu0) and loaded with iron sulfide (FeS) was prepared through a pyrolysis-liquid phase exfoliation process using waste soybean residue as the precursor biomass. Graphene-based catalyst (GBC) exhibits exceptional proficiency as a peroxymonosulfate activator, displaying a remarkable removal surpassing 90% of total petroleum hydrocarbons (TPHs) in 180 min. Reactive oxygen species were identified through masking experiments and electron paramagnetic resonance analysis in the Cu0/FeS/BC-900/PMS system. S(II) was the source of power for the conversion of Fe(III) to Fe(II), and it was also the reason for the continuous generation of SO4•− in the system. Density functional theory calculations revealed the active sites for adsorption and reaction. The presence of SO4•−, O2•−, and 1O2 species was attributed to the elongation of S–O and O–O bonds, as well as enhancement of electrons in sulfur and sp2 hybrid carbon atoms, respectively. The degradation of TPHs was ascribed to various radical and non-radical pathways of ROSs, with SO4•− serving as the primary oxidizing species. It was fascinating that the Cu0/FeS/BC-900/PMS system exhibited good resistance to inorganic anions and surfactants, and the treatment effect on real oilfield produced wastewater was satisfactory.

Potential of biochar for hydrocarbon degradation of crude oil-contaminated soils.

A greenhouse experiment was conducted to assess the effect of phytoremediation and biochar application on hydrocarbon degradation in crude oil-contaminated soils. The experiment consisted of four levels of biochar application (0, 5, 10, and 15 t/ha) and the presence or absence of Vigna unguiculata (cowpea; +C, -C) replicated thrice and arranged in a 4 × 2 × 3 factorial completely randomized design. Samples were taken on days 0, 30, and 60 for total petroleum hydrocarbon (TPH) analysis. A significantly higher TPH degradation efficiency of 69.2% (7033mg/kg) was observed in contaminated soils amended with 15 t/ha biochar only after 60 days of incubation. Highly significant interactions were observed between biochar × plant (p<0.001) and biochar × days (p=0.0073). Biochar also improved the growth of plants in contaminated soils, with the highest height of 23.50cm and stem girth of 2.10cm obtained when plants were amended with 15 t/ha biochar at 6weeks after planting. The potential of biochar to increase the degradation efficiency of hydrocarbons should be explored in the long run for the cleanup of crude oil-contaminated soils.

Assessment of Vinca rosea (Apocynaceae) Potentiality for Remediation of Crude Petroleum Oil Pollution of Soil

Petroleum oil pollution is a worldwide problem that results from the continuous exploration, production, and consumption of oil and its products. Petroleum hydrocarbons are produced as a result of natural or anthropogenic practices, and their common source is anthropogenic activities, which impose adverse effects on the ecosystem’s nonliving and living components including humans. Phytoremediation of petroleum hydrocarbon-polluted soils is an evolving, low-cost, and effective alternative technology to most traditional remediation methods. The objective of this study is to evaluate the phytoremediation potentiality of Vinca rosea for crude oil-contaminated soil by understanding its properties and involvement in the enhanced degradation of crude oil. The remediation potentiality was determined by evaluating the total petroleum hydrocarbon degradation percentage (TPH%) and changes in the molecular type composition of saturated and aromatic hydrocarbon fractions. TPH% was estimated gravimetrically, and changes in the molecular type composition of saturated and aromatic fractions were measured using gas chromatography and high-performance liquid chromatography, respectively. Sulfur concentration was measured using X-ray fluorescence. Cadmium and lead quantification was measured using Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The results revealed that V. rosea enhanced total petroleum hydrocarbon (TPH) degradation and altered the molecular composition of the crude oil. The saturated hydrocarbons increased and the aromatic hydrocarbons decreased. The saturated hydrocarbon fraction in the crude oil showed a wider spectrum of n-paraffin peaks than the oil extracted from unplanted and V. rosea-planted soils. Polyaromatic hydrocarbon degradation was enhanced in the presence of V. rosea, which was reflected in the increase of monoaromatic and diaromatic constituents. This was parallel to the increased sulfur levels in planted soil. The determination of sulfur and heavy metal content in plant organs indicated that V. rosea can extract and accumulate high amounts from polluted soils. The ability of V. rosea to degrade TPH and alter the composition of crude petroleum oil by decreasing the toxicity of polyaromatic hydrocarbons in soil, as well as its capability to absorb and accumulate sulfur and heavy metals, supports the use of plant species for the phytoremediation of crude oil-polluted sites.

Dose–effect of nitrogen regulation on the bioremediation of diesel contaminated soil

Nitrogen regulation is an effective method to enhance the bioremediation of hydrocarbon contamination. In this study, various dosages of two types of nitrogen sources were spiked to the diesel contaminated soil in a 60-day microcosmic experiment. The results showed that the total petroleum hydrocarbon (TPH) degradation rate improved from control test of 32.03% to the highest of 44.74% with nitrogen spiking. Peptone and KNO3 significantly improved the bioremediation of diesel-contaminated soil, peptone was more effective than KNO3 at low dosage. The soil C:N ratio of 20:1 (T1 treatment with the addition of peptone) was the optimal treatment. The effect of two nitrogen on soil pH was reverse, high dose of peptone addition significantly increased soil pH, but KNO3 addition significantly decreased soil pH. The soil bacteria diversity decreased significantly in the high dose Peptone treated soil, while the changes of bacteria diversity of KNO3 treated soil was just opposite. Furthermore, nitrogen regulation significantly changed the structure of soil bacterial community, Rubrobacter, Solirubrobacter and Gaiella, which belonging to Actinomycetota, were identified as the three common genus with hydrocarbon degrading ability in different nitrogen amended soil. Peptone and KNO3 had different mechanisms on the bioremediation of diesel contaminated soil. The properties of these two nitrogen sources provides us with more options for the bioremediation of hydrocarbon contaminated acid or alkaline soil.

Efficacy of bioadmendments in reducing the influence of salinity on the bioremediation of oil-contaminated soil

This study aimed to investigate the potential of three bioamendments (rice husk biochar, wheat straw biochar, and spent mushroom compost) to enhance microbial degradation of crude oil in saline soil. A soil microcosm experiment was conducted, comparing the response of soil microorganisms to crude oil under saline (1 % NaCl) and non-saline conditions. The soils were amended with different bioamendments at varying concentrations (2.5 % or 5 %), and degradation rates were monitored over a 120-day period at 20 °C. The results showed that the bioamendments significantly influenced the degradation of total petroleum hydrocarbons (TPH) in both non-saline and saline soils by 67 % and 18 % respectively. Non-saline soils exhibited approximately four times higher TPH biodegradation compared to saline soils. Among the bioamendments, rice husk biochar and spent mushroom compost had the greatest impact on biodegradation in saline soil, while wheat straw and rice husk biochar combined with spent mushroom compost showed the most significant effects in non-saline soil. The study also revealed that the bioamendments facilitated changes in the microbial community structure, particularly in the treatments with rice husk biochar and wheat straw biochar. Actinomycetes and fungi were found to be more tolerant to soil salinity, especially in the treatments with rice husk biochar and wheat straw biochar. Additionally, the production of CO2, indicating microbial activity, was highest (56 % and 60 %) in the treatments combining rice husk biochar or wheat straw biochar with spent mushroom compost in non-saline soil, while in saline soil rice husk biochar treatment (50 %) was the highest. Overall, this research demonstrates that the application of bioamendments, particularly rice husk biochar and wheat straw biochar combined with spent mushroom compost, can effectively enhance the biodegradation of crude oil in saline soil. These findings highlight the potential of such bioamendments as green and sustainable solutions for soil pollution, especially in the context of climate change-induced impacts on high-salinity soils, including coastal soils.

New insight into the effect of nitrogen on hydrocarbon degradation in petroleum-contaminated soil revealed through 15N tracing and flow cytometry

Nitrogen (N) has been widely used to dissipate total petroleum hydrocarbons (TPH) in the oil-contaminated soil, but the relationships of hydrocarbon transformation, N cycling and utilization, and microbial characteristics during TPH biodegradation still remain unclear. In this study, 15N tracers (K15NO3 and 15NH4Cl) were used as stimulants for TPH degradation to compare the bioremediation potential of TPH in the historically (5 a) and freshly (7 d) petroleum-contaminated soils. During bioremediation process, TPH removal and carbon balance, N transformation and utilization, as well as microbial morphologies were investigated using 15N tracing and flow cytometry. Results showed that TPH removal rates were higher in the freshly polluted soils (61.59 % for K15NO3 amendment and 48.55 % for 15NH4Cl amendment) than in the historically polluted soils (35.84 % for K15NO3 amendment and 32.30 % for 15NH4Cl amendment), and TPH removal rate through K15NO3 amendment was higher than that of 15NH4Cl in the freshly polluted soils. This result was attributed to the higher N gross transformation rates in the freshly contaminated soils (0.0034–0.432 mmol N kg−1 d−1) when compared with that in the historically contaminated soils (0.009–0.04 mmol N kg−1 d−1), which led to more TPH transformation to residual carbon (51.84 %–53.74 %) in the freshly polluted soils than that in the historically polluted soils (24.67 %–33.47 %). Based on the fluorescence intensity displayed by the combination of stains and cellular components to indicate microbial morphology and activity, flow cytometry analysis showed that nitrogen addition was beneficial for the membrane integrity of TPH-degrading bacteria, and nitrogen also enhanced DNA synthesis and activity of TPH-degrading fungi in freshly polluted soil. Correlation and structural equation modeling analysis identified that K15NO3 was beneficial to synthesize DNA of the TPH-degrading fungi but not the bacteria, which contributed to enhance TPH bio-mineralization in the soils with K15NO3 amendment.

Petroleum-Degrading Fungal Isolates for the Treatment of Soil Microcosms.

The main purpose of this study was to degrade total petroleum hydrocarbons (TPHs) from contaminated soil in batch microcosm reactors. Native soil fungi isolated from the same petroleum-polluted soil and ligninolytic fungal strains were screened and applied in the treatment of soil-contaminated microcosms in aerobic conditions. The bioaugmentation processes were carried out using selected hydrocarbonoclastic fungal strains in mono or co-cultures. Results demonstrated the petroleum-degrading potential of six fungal isolates, namely KBR1 and KBR8 (indigenous) and KBR1-1, KB4, KB2 and LB3 (exogenous). Based on the molecular and phylogenetic analysis, KBR1 and KB8 were identified as Aspergillus niger [MW699896] and tubingensis [MW699895], while KBR1-1, KB4, KB2 and LB3 were affiliated with the genera Syncephalastrum sp. [MZ817958], Paecilomyces formosus [MW699897], Fusarium chlamydosporum [MZ817957] and Coniochaeta sp. [MW699893], respectively. The highest rate of TPH degradation was recorded in soil microcosm treatments (SMT) after 60 days by inoculation with Paecilomyces formosus 97 ± 2.54%, followed by bioaugmentation with the native strain Aspergillus niger (92 ± 1.83%) and then by the fungal consortium (84 ± 2.21%). The statistical analysis of the results showed significant differences.

Characterization and genome analysis of Acinetobacter oleivorans S4 as an efficient hydrocarbon-degrading and plant-growth-promoting rhizobacterium

Plant-growth-promoting rhizobacteria (PGPR) have received increasing attention for assisting phytoremediation. However, the effect of PGPR on total petroleum hydrocarbon (TPH) degradation and plant growth promotion and its underlying mechanism is not well understood. In this study, phenotypic analysis and whole genome sequencing were conducted to comprehensively characterize a newly isolated rhizobacterium strain S4, which was identified as Acinetobacter oleivorans, from a TPH-contaminated soil. The strain degraded 62.5% of initially spiked diesel (1%) in minimal media within six days and utilized n-alkanes with a wide range of chain length (i.e., C12 to C40). In addition, the strain showed phenotypic traits beneficial to plant growth, including siderophore production, indole-3-acetic acid synthesis and phosphate solubilization. Potential metabolic pathways and genes encoding proteins responsible for the phenotypic traits were identified. In a real TPH-contaminated soil, inoculation of Acinetobacter oleivorans S4 significantly enhanced the growth of tall fescue relative to the soil without inoculation. In contrast, inoculation of Bacillus sp. Z7, a hydrocarbon-degrading strain, showed a negligible effect on the growth of tall fescue. The removal efficiency of TPH with inoculation of Acinetobacter oleivorans S4 was significantly higher than those without inoculation or inoculation of Bacillus sp. Z7. These results suggested that traits of PGPR beneficial to plant growth are critical to assist phytoremediation. Furthermore, heavy metal resistance genes and benzoate and phenol degradation genes were found in the genome of Acinetobacter oleivorans S4, suggesting its application potential in broad scenarios.

Fast degradation of macro alkanes through activating indigenous bacteria using biosurfactants produced by Burkholderia sp.

Soil bacteria that produce biosurfactants can use total petroleum hydrocarbons (TPHs) as a carbon source. This study demonstrated that biosurfactants produced by Burkholderia sp. enhanced the recovery and synergism of soil microbial community, resulting in fast degradation of macro alkanes. Experiments were carried out by applying bio-stimulation after pre-oxidation to investigate the effects of nutrient addition on biosurfactant production, TPH degradation, and microbial community succession in the soil. The results presented that bio-stimulation could produce biosurfactants in high C/N (32.6) and C/H (13.3) conversion after pre-oxidation and increased the total removal rate of TPH (10.59-46.71%). The number of total bacteria had a rapid increase trend (2.94-8.50 Log CFU/g soil). The degradation rates of macro alkanes showed a 4.0-fold (48.07mg/kg·d-1 versus 186.48mg/kg·d-1) increase, and the bioremediation time of degrading macro alkanes saved 166days. Further characterization revealed that the biosurfactants produced by Burkholderia sp. could activate indigenous bacteria to degrade macro alkanes rapidly. A shift in phylum from Actinomycetes to Proteobacteria was observed during bioremediation. The average relative abundance of the microbial community increased from 36.24 to 64.96%, and the predominant genus tended to convert from Allorhizobium (8.57%) to Burkholderia (15.95%) and Bacillus (15.70%). The co-occurrence network and Pearson correlation analysis suggested that the synergism of microbial community was the main reason for the fast degradation of macro alkanes in petroleum-contaminated soils. Overall, this study indicated the potential of the biosurfactants to activate and enhance the recovery of indigenous bacteria after pre-oxidation, which was an effective method to remediate petroleum-contaminated soils.

Remediation of petroleum contaminated soil by persulfate oxidation coupled with microbial degradation

This study was conducted on soil polluted with high concentrations of crude oil (12,835 ± 572.76 mg/kg) with different dosages of persulfate (PS) coupled with hydrocarbon-degrading mixed bacteria (including Enterobacteriaceae, Stenotrophomonas, Pseudomonas, Acinetobacter, and Achromobacter) obtained from long-term oil-contaminated soil. The interaction among total petroleum hydrocarbons (TPH), soil parameters, and microbial communities during a 187-d combined remediation process was evaluated. The result showed that the TPH removal of 1% PS oxidation combined with bioremediation was 80.05%; this was 4.88% and 20.94% higher than that of bioremediation and 1% PS oxidation combined with natural attenuation. This is a result of 1%PS stimulated enzyme secretion and dissolved organic carbon content, especially fulvic acid, improving TPH mobility and bioavailability in soil. Furthermore, introducing mixed bacteria after oxidation further increased enzyme activities and TPH-degrading ability, thus promoting carbon substrate conversion and biodegradation rate. Conversely, the excessive oxidation of 3% and 5% PS had a negative impact on the soil environment and microbial diversity resulting in lower TPH degradation (36%-57%). High-throughput sequencing revealed that the abundance and diversity of soil bacteria decreased in all remediation groups compared to those in the pristine soil. Redundancy analysis showed that the main factors affecting 1% PS oxidation combined with bioremediation during subsequent microbial remediation were pH, cation exchange capacity, and lipase activity, which may indirectly influence TPH biodegradation by increasing the abundance of genus Immundisolibacteraceae, Comamonadaceae, and Acinetobacter. This study provides data on in situ chemical oxidation integrated with the bioremediation of petroleum hydrocarbon-contaminated soils.

Effect of ultra-violet light radiation on Scenedesmus vacuolatus growth kinetics, metabolic performance, and preliminary biodegradation study.

This study presents the effect of ultra-violet (UV) light radiation on the process kinetics, metabolic performance, and biodegradation capability of Scenedesmus vacuolatus. The impact of the UV radiation on S. vacuolatus morphology, chlorophyll, carotenoid, carbohydrates, proteins, lipid accumulation, growth rate, substrate affinity and substrate versatility were evaluated. Thereafter, a preliminary biodegradative potential of UV-exposed S. vacuolatus on spent coolant waste (SCW) was carried out based on dehydrogenase activity (DHA) and total petroleum hydrocarbon degradation (TPH). Pronounced structural changes were observed in S. vacuolatus exposed to UV radiation for 24h compared to the 2, 4, 6, 12 and 48h UV exposure. Exposure of S. vacuolatus to UV radiation improved cellular chlorophyll (chla = 1.89-fold, chlb = 2.02-fold), carotenoid (1.24-fold), carbohydrates (4.62-fold), proteins (1.44-fold) and lipid accumulations (1.40-fold). In addition, the 24h UV exposed S. vacuolatus showed a significant increase in substrate affinity (1/Ks) (0.959), specific growth rate (µ) (0.024h-1) and biomass accumulation (0.513g/L) by 1.50, 2 and 1.9-fold respectively. Moreover, enhanced DHA (55%) and TPH (100%) degradation efficiency were observed in UV-exposed S. vacuolatus. These findings provided major insights into the use of UV radiation to enhance S. vacuolatus biodegradative performance towards sustainable green environment negating the use of expensive chemicals and other unfriendly environmental practices.