Microbial community evolution during the aerobic biodegradation of petroleum hydrocarbons in marine sediment microcosms: Effect of biostimulation and seasonal variations

Research on aquatic microcosm: Bibliometric analysis, toxicity comparison and model prediction

Recently, aquatic microcosms have attracted considerable attention because they can be used to simulate natural aquatic ecosystems. First, to evaluate the development of trends, hotspots, and national cooperation networks in the field, bibliometric analysis was performed based on 1841 articles on aquatic microcosm (1962-2022). The results of the bibliometric analysis can be categorized as follows: (1) Aquatic microcosm research can be summarized in two sections, with the first part focusing on the ecological processes and services of aquatic ecosystems, and the second focusing on the toxicity and degradation of pollutants. (2) The United States (number of publications: 541, proportion: 29.5%) and China (248, 13.5%) are the two most active countries. Second, to determine whether there is a difference between single-species and microcosm tests, that is, to perform different-tier assessments, the recommended aquatic safety thresholds in risk assessment [i.e., the community-level no effect concentration (NOECcommunity), hazardous concentrations for 5% of species (HC5) and predicted no effect concentration (PNEC)] were compared based on these tests. There was a significant difference between the NOECcommunity and HC5 (P < 0.05). Moreover, regression models predicting microcosm toxicity values were constructed to provide a reference for ecological systemic risk assessments based on aquatic microcosms.

Insight into the enhancement effect of humic acid on microbial degradation of triclosan in anaerobic sediments

Humic acid (HA) as one class of macromolecular substances plays important roles in mediating environmental behaviors of pollutants in sediments, but its effect on microbial degradation of triclosan (TCS), a common antibacterial drug, remains unclear. In this study, the effects of HA addition with different dosages (0-5%) on TCS degradation in anaerobic sediment slurries and the underlying microbial mechanisms were investigated. The results showed that HA addition significantly accelerated the TCS removal and the maximum removal percentage (30.2%) was observed in the sediment slurry with 5% HA addition. The iron reduction rate, relative abundances of the genera Comamonas, Pseudomonas and Geobacter, and bacterial network complexity in sediment slurry were significantly enhanced due to HA addition. Based on the partial least squares path modeling analysis, the enhancement effect of HA on TCS degradation was mainly explained by Fe(II):Fe(III) ratio with the highest influence on TCS removal (total effect: 0.723), followed by dominant genera abundances (total effect: 0.391), module relative abundance (total effect: 0.272), and network topological features (total effect: 0.263). This finding enhanced our understanding of the role of HA in TCS biodegradation in contaminated sediments for bioremediation purposes.

Efficient degradation and mineralization of aniline in aqueous solution by new dielectric barrier discharge non-thermal plasma

Aniline is a priority pollutant that is unfavorable to the environment and human health due to its carcinogenic and mutagenic nature. The performance of the dielectric barrier discharge reactor was examined based on the aniline degradation efficiency. Different parameters were studied and optimized to treat various wastewater conditions. Role of active species for aniline degradation was investigated by the addition of inhibitors and promoters. The optimum conditions were 20 mg/L initial concentration, 1.8 kV applied voltage, 4 L/min gas flow rate and a pH of 8.82. It was observed that 87% of aniline was degraded in 60 min of dielectric barrier discharge treatment at optimum conditions. UV-Vis spectra showed gradual increase in the treatment efficiency of aniline with the propagation of treatment time. Mineralization of AN was confirmed by TOC measurement and a decrease in pH during the process. To elicit the aniline degradation route, HPLC and LC-MS techniques were used to detect the intermediates and byproducts. It was identified that aniline degraded into different organic byproducts and was dissociated into carbon dioxide and water. Comparison of the current system with existing advanced oxidation processes showed that DBD has a remarkable potential for the elimination of organic pollutants.

Response of partial nitritation and denitrification processes to high levels of free ammonia in a pilot mature landfill leachate treatment system: Stability and microbial community dynamics

The high levels of free ammonia (FA) challenge the application of partial nitritation (PN) and denitrification (DN) in the treatment of ammonia-rich wastewater. This study explored the impact of high levels of FA on the PN and DN stability and microbial community dynamics. By reducing reflux and increasing influent load, the concentrations of FA in PN and DN reactors increased from 28.9 mg/L and 140.0 mg/L to 1099.8 mg/L and 868.4 mg/L, respectively. During this process, the performance of PN and DN remained stable. The microbial analysis revealed that the Nitrosomonas exhibited strong tolerance to high levels of FA, and its relative abundance was positively correlated with amoABC (R2 0.984) and hao (R2 0.999) genes. The increase in microbial diversity could enhance the resistance ability of PN against the FA impact. In contrast, high levels of FA had scant influence on the microbial community and performance of DN.

Spatio-temporal variation of the microbial community of the coast of Lebanon in response to petroleum hydrocarbon pollution

In this study, the coast of Lebanon was analyzed for the dynamic changes in sediment microbial communities in response to a major petroleum oil spill and tar contamination that occurred in the summer of 2021. Spatio-temporal variations in the microbial structure along the shores of Lebanon were assessed in comparison to baseline microbial structure determined in 2017. Microbial community structure and diversity were determined using Illumina MiSeq technology and DADA2 pipeline. The results show a significant diversity of microbial populations along the Lebanese shore, and a significant change in the sediment microbial structure within four years. Namely, Woeseia, Blastopirellula, and Muriicola were identified in sediment samples collected in year 2017, while a higher microbial diversity was observed in 2021 with Woeseia, Halogranum, Bacillus, and Vibrio prevailing in beach sediments. In addition, the results demonstrate a significant correlation between certain hydrocarbon degraders, such as Marinobacter and Vibrio, and measured hydrocarbon concentrations.

Effects of biodegradation, biotoxicity and microbial community on biostimulation of sulfolane

To evaluate the effectiveness of biostimulation in remediating soil-free groundwater and groundwater with soil, experiments were conducted using soil and groundwater samples that were contaminated with sulfolane. The main objective was to characterize the differences in sulfolane removal efficiency and biotoxicity between in situ soil-free groundwater and groundwater with soil and different concentrations of dissolved oxygen (1 mg/L and 5 mg/L) and various nutrient salts (in situ and spiked). Optimizing the nutrient salt conditions improved the removal efficiency of sulfolane by 1.8-6.5 that under in situ nutrient salt conditions. Controlling the dissolved oxygen concentration enhanced the efficiency of removal of sulfolane by 1.5-4.5 times over that at the simulated in situ dissolved oxygen concentration, suggesting that the degradation of sulfolane by indigenous microorganisms requires nutrient salts more than it requires dissolved oxygen. Biotoxicity data showed that the luminescence inhibition of Aliivibrio fischeri by sulfolane was lower in the biostimulated samples than in the pre-treated samples. Biostimulation reduced the biotoxicity of the treated samples by 42-51%, revealing that it was effective in removing sulfolane and reducing biotoxicity. Microbial community analysis showed that the biostimulation did not change the dominant species in the original in situ community, and increased the proportion of sulfolane-degraders. The outcome of this study can be used to set parameters for the remediation of groundwater that is contaminated by sulfolane in oil refineries.

Biodegradation of petroleum hydrocarbons based pollutants in contaminated soil by exogenous effective microorganisms and indigenous microbiome

Microbial remediation is an eco-friendly and promising approach for the restoration of sites contaminated by petroleum hydrocarbons (PHCs). The degradation of total petroleum hydrocarbons (TPHs), semi volatile organic compounds (SVOCs) and volatile organic compounds (VOCs) of the soil samples collected from a petrochemical site by indigenous microbiome and exogenous microbes (Saccharomyces cerevisiae ATCC 204508/S288c, Candida utilis AS2.281, Rhodotorula benthica CBS9124, Lactobacillus plantarum S1L6, Bacillus thuringiensis GDMCC1.817) was evaluated. Community structure and function of soil microbiome and the mechanism involved in degradation were also revealed. After bioremediation for two weeks, the concentration of TPHs in soil samples was reduced from 17,800 to 13,100 mg/kg. The biodegradation efficiencies of naphthalene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene, 1,2,3-trichloropropane, 1,2-dichloropropane, ethylbenzene and benzene in soil samples with the addition of S. cerevisiae were 38.0%, 35.7%, 36.2%, 40.4%, 33.6%, 36.2%, 12.0%, 43.9%, 43.3% and 43.0%, respectively. The microbial diversity and community structure were improved during the biodegradation process. S. cerevisiae supplemented soil samples exhibited the highest relative abundance of the genus Acinetobacter for bacteria and Saccharomyces for yeast. The findings offer insight into the correlation between microbes and the degradation of PHC-based pollutants during the bioremediation process.

Improving soil fertility by driving microbial community changes in saline soils of Yellow River Delta under petroleum pollution

It is promising to use indigenous microorganisms for fertility improvement in petroleum-contaminated coastal soil. As a result, the microbial community and physicochemical property are the base for the restoration. For the detailed information, the Phragmites Communis (P), Chinese Tamarisk (C), Suaeda salsa (S), and new Bare Land (B) soil of Yellow River Delta was 90 g in 100 mL sterile bottles simulated at 25 °C with soil: petroleum = 10:1 in the incubator for four months. The samples were detected at 60 and 120 days along with untreated soil and aged Oil Sludge (O) as control. The results showed that all the samples were alkaline (pH 7.99-8.83), which the salinity and NO₃^- content of incubate soil followed the in situ samples as P (1.09-1.72‰, 8.02-8.17 mg kg^-1), C (10.61-13.79‰, 5.99-6.07 mg kg^-1), S (10.19-12.43‰, 3.64-4.22 mg kg^-1), B (31.85-32.45‰, 3.56-3.72 mg kg^-1) and O (31.61-34.30‰, 0.89-0.90 mg kg^-1). NO₃^- and organic carbon decreased after incubation, which the polluted samples (86.63-92.63 g kg^-1) still had higher organic carbon than untreated ones with more NH₄⁺ consumption. The high-throughput sequence results showed that the Gammaproteobacteria and Alphaproteobacteria were dominant in all samples, while sulfate reducting bacteria Alphaproteobacteria decreased at 120 days. Meanwhile, the electroactive Gammaproteobacteria might symbiosis with Methanosaetaceae and Methanosarcinaceae, degrading petroleum after electron receptors depletion. Nitrososphaeraceae and Nitrosopumilaceae oxidise NH₄⁺ to NO₂^- for intra-aerobic anaerobes and denitrifying bacteria producing oxygen for biodegradation in polluted Phragmites Communis soil. The halotolerant Halomicrobiaceae and Haloferacaceae predominated in saline Chinese Tamarisk, Suaeda Salsa and Bare Land, which were potential electroactive degradater. As the ageing sludge formed, the hydrogen trophic methanogens Methanothermobacteraceae (73.90-92.72%) was prevalent with the petroleum pollution. In conclusion, petroleum initiated two-phase in the sludge forming progress: electron acceptor consumption and electron transfer between degradater and methanogens. Based on the results, the domestic sewage N, P removal coupling and electron transport will be the basement for polluted soils fertility improvement.

A latest review on the application of microcosm model in environmental research

Microcosms are used experimentally to simulate ecosystems. This technology has received increasing attention and is widely used for environmental research. This review briefly introduces the origin and development of microcosm theory, summarizes classification and applications of microcosms across decades, and describes the advantages and limitations of microcosm technology in comparison with other methods. Finally, trends in the development of microcosm models are discussed.

Bioremediation perspectives and progress in petroleum pollution in the marine environment: a review

The marine environment is often affected by petroleum hydrocarbon pollution due to industrial activities and petroleum accidents. This pollution has recalcitrant and persistent compounds that pose a high risk to the ecological system and human health. For this reason, the world claims to seek to clean up these pollutants. Bioremediation is an attractive approach for removing petroleum pollution. It is considered a low-cost and highly effective approach with fewer side effects compared to chemical and physical techniques. This depends on the metabolic capability of microorganisms involved in the degradation of hydrocarbons through enzymatic reactions. Bioremediation activities mostly depend on environmental conditions such as temperature, pH, salinity, pressure, and nutrition availability. Understanding the effects of environmental conditions on microbial hydrocarbon degraders and microbial interactions with hydrocarbon compounds could be assessed for the successful degradation of petroleum pollution. The current review provides a critical view of petroleum pollution in seawater, the bioavailability of petroleum compounds, the contribution of microorganisms in petroleum degradation, and the mechanisms of degradation under aerobic and anaerobic conditions. We consider different biodegradation approaches such as biostimulation, bioaugmentation, and phytoremediation.

Hydrocarbon transformation pathways and soil organic carbon stability in the biostimulation of oil-contaminated soil: Implications of 13C natural abundance

Mineralization, assimilation, and humification are key processes to detoxify oil-contaminated soil by biostimulation remediation strategies, and these processes are affected by stimulants. In this study, we investigated the effects of either inorganic salts or organic stimulants (organic compost and sawdust) on hydrocarbon transformation. Total petroleum hydrocarbons (TPH) and hydrocarbon components were determined by gravimetry and gas chromatography, and the ¹³C of CO₂, microbial biomass carbon (MBC), and humus were measured by stable isotope mass spectrometry. The results showed that organic compost was the most beneficial for the dissipation of hydrocarbons. After 60 days of remediation, the removal rates of TPH, saturates, aromatics, C7-C30 n-alkanes, and 16 PAHs were 35.7%, 39.6%, 15.9%, 80.5%, and 8.8%, respectively. A total of 84.7%-88.5% of the removed hydrocarbons were mineralized in all the treatments. The hydrocarbon degradation pathway in the control soil (without stimulant addition) was "assimilation → humification → mineralization". The hydrocarbon transformation pathways in the biostimulation treatments were "assimilation → mineralization → humification". The soil organic carbon (SOC) stability decreased during remediation, which was attributed to the enhanced microbial activity and the removal of recalcitrant hydrocarbons.

Port Sediments: Problem or Resource? A Review Concerning the Treatment and Decontamination of Port Sediments by Fungi and Bacteria

Contamination of marine sediments by organic and/or inorganic compounds represents one of the most critical problems in marine environments. This issue affects not only biodiversity but also ecosystems, with negative impacts on sea water quality. The scientific community and the European Commission have recently discussed marine environment and ecosystem protection and restoration by sustainable green technologies among the main objectives of their scientific programmes. One of the primary goals of sustainable restoration and remediation of contaminated marine sediments is research regarding new biotechnologies employable in the decontamination of marine sediments, to consider sediments as a resource in many fields such as industry. In this context, microorganisms—in particular, fungi and bacteria—play a central and crucial role as the best tools of sustainable and green remediation processes. This review, carried out in the framework of the Interreg IT-FR Maritime GEREMIA Project, collects and shows the bioremediation and mycoremediation studies carried out on marine sediments contaminated with ecotoxic metals and organic pollutants. This work evidences the potentialities and limiting factors of these biotechnologies and outlines the possible future scenarios of the bioremediation of marine sediments, and also highlights the opportunities of an integrated approach that involves fungi and bacteria together.

Effect of C/N substrates for enhanced extracellular polymeric substances (EPS) production and Poly Cyclic Aromatic Hydrocarbons (PAHs) degradation

Extracellular Polymeric Substances (EPS) influenced Poly Cyclic Aromatic Hydrocarbons (PAHs) degrading Klebsiella pneumoniae was isolated from the marine environment. To increase the EPS production by Klebsiella pneumoniae, several physicochemical parameters were tweaked such as different carbon sources (arabinose, glucose, glycerol, lactose, lactic acid, mannitol, sodium acetate, starch, and sucrose at 20 g/L), nitrogen sources (ammonium chloride, ammonium sulphate, glycine, potassium nitrate, protease peptone and urea at 2 g/L), different pH, carbon/nitrogen ratio, temperature, and salt concentration were examined. Maximum EPS growth and biodegradation of Anthracene (74.31%), Acenaphthene (67.28%), Fluorene (62.48%), Naphthalene (57.84%), and mixed PAHs (55.85%) were obtained using optimized conditions such as glucose (10 g/L) as carbon source, potassium nitrate (2 g/L) as the nitrogen source at pH 8, growth temperature of 37 °C, 3% NaCl concentration and 72 h incubation period. The Klebsiella pneumoniae biofilm architecture was studied by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). The present study demonstrates the EPS influenced PAHs degradation of Klebsiella pneumoniae.