Comparison the effects of bioaugmentation versus biostimulation on marine microbial community by PCR-DGGE: A mesocosm scale

Microbial degradation mechanisms of surface petroleum contaminated seawater in a typical oil trading port

Petroleum hydrocarbons are significant new persistent organic pollutants for marine oil spill risk areas. Oil trading ports, in turn, have become major bearers of the risk of offshore oil pollution. However, studies on the molecular mechanisms of microbial degradation of petroleum pollutants by natural seawater are limited. Here, an in situ microcosm study was conducted. Combined with metagenomics, differences in metabolic pathways and in the gene abundances of total petroleum hydrocarbons (TPH) are revealed under different conditions. About 88% degradation of TPH was shown after 3 weeks of treatment. The positive responders to TPH were concentrated in the genera Cycloclasticus, Marivita and Sulfitobacter of the orders Rhodobacterales and Thiotrichales. The genera Marivita, Roseobacter, Lentibacter and Glaciecola were key degradation species when mixing dispersants with oil, and all of the above are from the Proteobacteria phylum. The analysis showed that the biodegradability of aromatic compounds, polycyclic aromatic hydrocarbon and dioxin were enhanced after the oil spill, and genes with higher abundances of bphAa, bsdC, nahB, doxE and mhpD were found, but the photosynthesis-related mechanism was inhibited. The dispersant treatment effectively stimulated the microbial degradation of TPH and then accelerated the succession of microbial communities. Meanwhile, functions such as bacterial chemotaxis and carbon metabolism (cheA, fadeJ and fadE) were better developed, but the degradation of persistent organic pollutants such as polycyclic aromatic hydrocarbons was weakened. Our study provides insights into the metabolic pathways and specific functional genes for oil degradation by marine microorganisms and will help improve the application and practice of bioremediation.

Prospects in the bioremediation of petroleum hydrocarbon contaminants from hypersaline environments: A review

Hypersaline environments are underappreciated and are frequently exposed to pollution from petroleum hydrocarbons. Unlike other environs, the high salinity conditions present are a deterrent to various remediation techniques. There is also production of hypersaline waters from oil-polluted ecosystems which contain toxic hydrophobic pollutants that are threat to public health, environmental protection, and sustainability. Currently, innovative advances are being proposed for the remediation of oil-contaminated hypersaline regions. Such advancements include the exploration and stimulation of native microbial communities capable of utilizing and degrading petroleum hydrocarbons. However, prevailing salinity in these environments is unfavourable for the growth of non-halophylic microorganisms, thus limiting effective bioremediation options. An in-depth understanding of the potentials of various remediation technologies of hydrocarbon-polluted hypersaline environments is lacking. Thus, we present an overview of petroleum hydrocarbon pollution in hypersaline ecosystems and discuss the challenges and prospects associated with several technologies that may be employed in remediation of hydrocarbon pollution in the presence of delimiting high salinities. The application of biological remediation technologies including the utilization of halophilic and halotolerant microorganisms is also discussed.

Bioaugmentation as a green technology for hydrocarbon pollution remediation. Problems and prospects

Environmental pollution mitigation measure involving bioremediation technology is a sustainable intervention for a greener ecosystem biorecovery, especially the obnoxious hydrocarbons, xenobiotics, and other environmental pollutants induced by anthropogenic stressors. Several successful case studies have provided evidence to this paradigm including the putative adoption that the technology is eco-friendly, cost-effective, and shows a high tendency for total contaminants mineralization into innocuous bye-products. The present review reports advances in bioremediation, types, and strategies conventionally adopted in contaminant clean-up. It identified that natural attenuation and biostimulation are faced with notable limitations including the poor remedial outcome under the natural attenuation system and the residual contamination occasion following a biostimulation operation. It remarks that the use of genetically engineered microorganisms shows a potentially promising insight as a prudent remedial approach but is currently challenged by few ethical restrictions and the rural unavailability of the technology. It underscores that bioaugmentation, particularly the use of high cell density assemblages referred to as microbial consortia possess promising remedial prospects thus offers a more sustainable environmental security. The authors, therefore, recommend bioaugmentation for large scale contaminated sites in regions where environmental degradation is commonplace.

Microbial Community Dynamics during Biodegradation of Crude Oil and Its Response to Biostimulation in Svalbard Seawater at Low Temperature

The development of oil exploration activities and an increase in shipping in Arctic areas have increased the risk of oil spills in this cold marine environment. The objective of this experimental study was to assess the effect of biostimulation on microbial community abundance, structure, dynamics, and metabolic potential for oil hydrocarbon degradation in oil-contaminated Arctic seawater. The combination of amplicon-based and shotgun sequencing, together with the integration of genome-resolved metagenomics and omics data, was applied to assess microbial community structure and metabolic properties in naphthenic crude oil-amended microcosms. The comparison of estimates for oil-degrading microbial taxa obtained with different sequencing and taxonomic assignment methods showed substantial discrepancies between applied methods. Consequently, the data acquired with different methods was integrated for the analysis of microbial community structure, and amended with quantitative PCR, producing a more objective description of microbial community dynamics and evaluation of the effect of biostimulation on particular microbial taxa. Implementing biostimulation of the seawater microbial community with the addition of nutrients resulted in substantially elevated prokaryotic community abundance (103-fold), a distinctly different bacterial community structure from that in the initial seawater, 1.3-fold elevation in the normalized abundance of hydrocarbon degradation genes, and 12% enhancement of crude oil biodegradation. The bacterial communities in biostimulated microcosms after four months of incubation were dominated by Gammaproteobacterial genera Pseudomonas, Marinomonas, and Oleispira, which were succeeded by Cycloclasticus and Paraperlucidibaca after eight months of incubation. The majority of 195 compiled good-quality metagenome-assembled genomes (MAGs) exhibited diverse hydrocarbon degradation gene profiles. The results reveal that biostimulation with nutrients promotes naphthenic oil degradation in Arctic seawater, but this strategy alone might not be sufficient to effectively achieve bioremediation goals within a reasonable timeframe.

Bioremediation of Total Petroleum Hydrocarbons (TPH) by Bioaugmentation and Biostimulation in Water with Floating Oil Spill Containment Booms as Bioreactor Basin

A crude oil spill is a common issue during offshore oil drilling, transport and transfer to onshore. Second, the production of petroleum refinery effluent is known to cause pollution due to its toxic effluent discharge. Sea habitats and onshore soil biota are affected by total petroleum hydrocarbons (TPH) as a pollutant in their natural environment. Crude oil pollution in seawater, estuaries and beaches requires an efficient process of cleaning. To remove crude oil pollutants from seawater, various physicochemical and biological treatment methods have been applied worldwide. A biological treatment method using bacteria, fungi and algae has recently gained a lot of attention due to its efficiency and lower cost. This review introduces various studies related to the bioremediation of crude oil, TPH and related petroleum products by bioaugmentation and biostimulation or both together. Bioremediation studies mentioned in this paper can be used for treatment such as emulsified residual spilled oil in seawater with floating oil spill containment booms as an enclosed basin such as a bioreactor, for petroleum hydrocarbons as a pollutant that will help environmental researchers solve these problems and completely clean-up oil spills in seawater.

Mesocosm-based simulations to optimize a bioremediation strategy for the effective restoration of wildfire-impacted soils contaminated with high-molecular-weight hydrocarbons

AIMS

We obtained four microbial isolates from soil exposed to forest fire and evaluated their potential bioremediation activity when combined with a biosurfactant-producing bacterial strain for the decontamination of wildfire-impacted soil polluted with high-molecular-weight (HMW) hydrocarbons.

METHODS AND RESULTS

We established mesocosm trials to compare three bioremediation strategies: natural attenuation, bioaugmentation and biostimulation. Chemical analysis, culture-dependent and culture-independent methods were used to evaluate the bioremediation efficiency and speciation of the microbial cenoses based on these approaches. After treatment for 90 days, bioaugmentation removed 75·2-75·9% of the HMW hydrocarbons, biostimulation removed 63·2-69·5% and natural attenuation removed ~22·5%. Hydrocarbon degradation was significantly enhanced in the mesocosm supplemented with the biosurfactant-producing bacterial strain after 20 and 50 days of treatment compared to the other bioremediation strategies.

CONCLUSIONS

We found that the bioaugmentation approach was more effective than biostimulation and natural attenuation for the removal of HMW hydrocarbons from fire-impacted soil.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study showed that micro-organisms from wildfire-impacted soil show significant potential for bioremediation, and that biosurfactant-producing bacterial strains can be combined with them as part of an effective bioremediation strategy.

Crude oil pollution and biodegradation at the Persian Gulf: A comprehensive and review study

The Persian Gulf consider as the fundamental biological marine condition between the seas. There is a different assortment of marine life forms including corals, wipes, and fish in this marine condition. Mangrove timberlands are found all through this sea-going biological system. Sullying of the Persian Gulf to oil-based goods is the principle of danger to this marine condition and this contamination can effectively affect this differing marine condition. Numerous specialists examined the result of oil contamination on Persian Gulf marine creatures including corals sponges, bivalves, and fishes. These analysts affirmed this oil contamination on the Persian Gulf significantly diminished biodiversity. Diverse microorganisms fit to consume oil-based commodities detailed by various scientists from the Persian Gulf and their capacity to the debasement of unrefined petroleum has been examined. There has additionally been little exploration of cyanobacteria, yeast, and unrefined petroleum debasing organisms in this sea-going environment. Biosurfactants are amphipathic molecules that upgrade the disintegration of oil and increment their bioavailability to corrupt microscopic organisms. Additionally, biosurfactant-producing bacteria were discovered from the Persian Gulf, and the capability to degradation of crude oil in microscale was evaluated. The current review article aims to collect the finding of various researches performed in the Persian Gulf on oil pollution and crude-oil biodegradation. It is expected that by applying biological methods in combination with mechanical and chemical methods, the hazard consequences of crude-oil contamination on this important aquatic ecosystem at the world will be mitigated and a step towards preserving this diverse marine environment.

Feasibility Study of Activated Sludge/Contact Aeration Combined System Treating Oil-Containing Domestic Sewage

Both activated sludge/contact aeration (AS/CA) and AS-only systems for treating oil-containing domestic sewage were tested. The results of these tests indicate that the oil and grease removal ratios of the AS/CA system exceeded those of the AS-only system. When the influent oil and grease concentration reached 60 mg/L, the effluent concentration of the AS system was 13 mg/L, which exceed 10 mg/L, the Taiwan Effluent Standard for oil and grease. However, in the AS/CA system, the effluent oil and grease concentration was 8 mg/L, which was below the required standard. This study analyzes the biological phases of the AS-only system and the combined AS/CA system using a scanning electronic microscope and a denatured gradient gel electrophoresis method when the inflow concentration of oil and grease is increased to 120 mg/L. The results of the Chemical Oxygen Demand (COD) experiment reveal that the AS/CA system is affected less than the AS system, and the COD removal rate of the AS/CA system is maintained at 81%, which exceeds that (61.5%) of the AS-only system. The analytical results thus obtained suggest that both the amounts of biological phase and the biomass in the combined AS/CA system exceed those of an AS-only system.

Microcosm evaluation of the impact of oil contamination and chemical dispersant addition on bacterial communities and sediment remediation of an estuarine port environment

AIM

To evaluate the interactive effects of oil contamination and chemical dispersant application on bacterial composition and sediment remediation of an estuarine port environment.

METHODS AND RESULTS

A multifactorial controlled microcosm experiment was set up using sediment cores retrieved from an estuarine port area located at Ria de Aveiro lagoon (Aveiro, Portugal). An oil spill with and without chemical dispersant addition was simulated. Sediment oil hydrocarbon concentrations and benthic bacterial community structure were evaluated by GC-MS and 16S rRNA high-throughput sequencing respectively. Although initially (first 10 days) chemical dispersion of oil enhanced the concentrations of the heavier polycyclic aromatic hydrocarbons and of the C₂₂ -C₃₀ alkane group, with time (21 days), no significant differences in hydrocarbon concentrations were detected among treatments. Moreover, no significant changes were detected in the structure of sediment bacterial communities, which mainly consisted of operational taxonomic units related to hydrocarbon-contaminated marine environments. We hypothesize that the environmental background of the sampling site preconditioned the communities' response to additional contamination.

CONCLUSION

This experimental microcosm study showed that the chemical dispersion of oil did not influence sediment remediation or bacterial community composition.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study showed that chemical dispersion of oil may not improve the remediation of port sediments. Further studies are needed to investigate the impact of chemical dispersants in combination with bioremediation strategies on the process of sediment remediation in port areas.

Degradation of phenol at high concentrations using immobilization of Pseudomonas putida P53 into sawdust entrapped in sodium-alginate beads

Phenols are distributed either as natural or artificial mono-aromatic compounds in various environmental sites as major pollutants. The objective of this study was the immobilization of the phenol degrading bacteria P. putida P53 and A. scleromae P69 in sodium-alginate beads and sawdust as carriers and evaluate the biodegradation ability. The biodegradation ability of strains in free form were evaluated and P. putida P53 was shown to biodegrade up to 1,800 mg/L phenol. Bacterial biomass was prepared and attached to carrier with entrapment and attachment methods. Prepared beads were added to Erlenmeyer flasks containing different concentrations of phenol in BH medium (1,800, 2,200, 2,600 and 3,000 mg/L). According to the results, phenol biodegradation efficiency of immobilized bacteria in sawdust was more than free form. Strain P53 had better biodegradation than P69 strain. Attachment and entrapments into carriers had positive results, Scanning electron micrograph (SEM) images indicated that alginate beads were globular shapes (10 nm), and strains aggregated between the large cavities of the matrix. Comparison of sawdust and alginate as carriers for degradation of phenol at high concentrations demonstrated that sawdust improved biodegradation better, and immobilized P53 into sawdust entrapped in sodium-alginate beads can be used for biodegradation purposes.

Separating and characterizing functional alkane degraders from crude-oil-contaminated sites via magnetic nanoparticle-mediated isolation

Uncultivable microorganisms account for over 99% of all species on the planet, but their functions are yet not well characterized. Though many cultivable degraders for n-alkanes have been intensively investigated, the roles of functional n-alkane degraders remain hidden in the natural environment. This study introduces the novel magnetic nanoparticle-mediated isolation (MMI) technology in Nigerian soils and successfully separates functional microbes belonging to the families Oxalobacteraceae and Moraxellaceae, which are dominant and responsible for alkane metabolism in situ. The alkR-type n-alkane monooxygenase genes, instead of alkA- or alkP-type, were the key functional genes involved in the n-alkane degradation process. Further physiological investigation via a BIOLOG PM plate revealed some carbon (Tween 20, Tween 40 and Tween 80) and nitrogen (tyramine, l-glutamine and d-aspartic acid) sources promoting microbial respiration and n-alkane degradation. With further addition of promoter carbon or nitrogen sources, the separated functional alkane degraders significantly improved n-alkane biodegradation rates. This suggests that MMI is a promising technology for separating functional microbes from complex microbiota, with deeper insight into their ecological functions and influencing factors. The technique also broadens the application of the BIOLOG PM plate for physiological research on functional yet uncultivable microorganisms.