Phytomediated biostimulation of the autochthonous bacterial community for the acceleration of the depletion of polycyclic aromatic hydrocarbons in contaminated sediments

Characteristic microbiome and synergistic mechanism by engineering agent MAB-1 to evaluate oil-contaminated soil biodegradation in different layer soil

Bioremediation is a sustainable and pollution-free technology for crude oil-contaminated soil. However, most studies are limited to the remediation of shallow crude oil-contaminated soil, while ignoring the deeper soil. Here, a high-efficiency composite microbial agent MAB-1 was provided containing Bacillus (naphthalene and pyrene), Acinetobacter (cyclohexane), and Microbacterium (xylene) to be synergism degradation of crude oil components combined with other treatments. According to the crude oil degradation rate, the up-layer (63.64%), middle-layer (50.84%), and underlying-layer (54.21%) crude oil-contaminated soil are suitable for bioaugmentation (BA), biostimulation (BS), and biostimulation+bioventing (BS+BV), respectively. Combined with GC-MS and carbon number distribution analysis, under the optimal biotreatment, the degradation rates of 2-ring and 3-ring PAHs in layers soil were about 70% and 45%, respectively, and the medium and long-chain alkanes were reduced during the remediation. More importantly, the relative abundance of bacteria associated with crude oil degradation increased in each layer after the optimal treatment, such as Microbacterium (2.10-14%), Bacillus (2.56-12.1%), and Acinetobacter (0.95-12.15%) in the up-layer soil; Rhodococcus (1.5-6.9%) in the middle-layer soil; and Pseudomonas (3-5.4%) and Rhodococcus (1.3-13.2%) in the underlying-layer soil. Our evaluation results demonstrated that crude oil removal can be accelerated by adopting appropriate bioremediation approach for different depths of soil, providing a new perspective for the remediation of actual crude oil-contaminated sites.

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.

Degradation of BTEX mixture by a new Pseudomonas putida strain: role of the quorum sensing in the modulation of the upper BTEX oxidative pathway

A new Pseudomonas putida strain (AQ8) was isolated from a decommissioned oil refinery's soil in Italy and characterized for its ability to degrade BTEX. The draft genome of the new strain was sequenced and annotated for genes that encode enzymes putatively involved in BTEX degradation and quorum sensing. The strain was transformed with a plasmid expressing lactonase, which cleaves the autoinducer quorum sensing signal molecule, the acyl-homoserine lactone, to obtain a quorum sensing minus strain. P. putida AQ8 depleted the 40% on average of all the components of the initial BTEX concentration in 36 h. The quorum sensing minus strain, in the same time interval, depleted only the 10% of the initial BTEX concentration. The role of quorum sensing in regulating the expression of the annotated benzene/toluene dioxygenase gene (benzA) and biphenyl/toluene/benzene dioxygenase (bphA) genes, which are involved in BTEX degradation, was studied by quantitative RT-real-time quantitative (q)PCR analysis. The qPCR data showed decreased levels of expression of the benzA and bphA genes in the quorum sensing minus strain. Our results showed, for the first time, quorum sensing modulation of the level of transcription of dioxygenase genes in the upper BTEX oxidation pathway.

Arbuscular mycorrhizal and microbial profiles of an aged phenol-polynuclear aromatic hydrocarbon-contaminated soil

Arbuscular mycorrhizal fungi (AMF) are ubiquitous, obligatory plant symbionts that have a beneficial influence on plants in contaminated environments. This study focused on evaluating the biomass and biodiversity of the AMF and microbial communities associated with Poa trivialis and Phragmites australis plants sampled at an aged site contaminated with phenol and polynuclear aromatic hydrocarbons (PAHs) and an uncontaminated control site. We analyzed the soil phospholipid fatty acid profile to describe the general structure of microbial communities. PCR-denaturing gradient gel electrophoresis with primers targeting the 18S ribosomal RNA gene was used to characterize the biodiversity of the AMF communities and identify dominant AMF species associated with the host plants in the polluted and control environments. The root mycorrhizal colonization and AMF biomass in the soil were negatively affected by the presence of PAHs and phenol, with no significant differences between the studied plant species, whereas the biodiversity of the AMF communities were influenced by the soil contamination and plant species. Soil contamination was more detrimental to the biodiversity of AMF communities associated with Ph. australis, compared to P. trivialis. Both species favored the development of different AMF species, which might be related to the specific features of their different root systems and soil microbial communities. The contaminated site was dominated by AMF generalists like Funneliformis and Rhizophagus, whereas in the control site Dominikia, Archaeospora, Claroideoglomus, Glomus, and Diversispora were also detected.

Enhancing the degradation of mixed polycyclic aromatic hydrocarbon and medium-chain-length polyhydroxyalkanoate production by mixed bacterial cultures using modified repeated batch fermentation

AIMS

To increase the biodegradation of phenanthrene (PHE), pyrene (PYR) and fluoranthene (FLU) through mixed cultures of polycyclic aromatic hydrocarbon (PAH)-degrading bacteria, using modified repeated batch fermentation.

METHODS AND RESULTS

Novel bacterial strains of Pseudomonas putida, Pseudomonas sp. and Ralstonia eutropha were cultivated and the biodegradation and conversion of mixed PAH to medium-chain-length polyhydroxyalkanoates (MCL-PHA) was determined. The highest degradation of PAH (100%) and PHA production (50·0%) was obtained in medium containing 30 mmol l^-1 of mixed PAH after three cycles of repeated batch fermentation. The concentration of PAH in the reactor was increased from 30 to 90 mmol l^-1 with repeated additions of PAH, and bacteria were able to produce PHA at 40% of cell dry mass. The MCL-PHA were identified by gas chromatography/mass spectroscopy, with the 3-hydroxydecanoate (3-HD) monomer higher than 75 mol.%.

CONCLUSIONS

This study demonstrated that the biodegradation of PHE, PYR and FLU was enhanced by modified repeated batch fermentation using a mixed culture of bacteria. In addition, this fermentation strategy also increased the production of PHA, with an increase in monomer composition.

SIGNIFICANCE AND IMPACT OF THE STUDY

This was the first study to describe the enhancement of the degradation of mixed solutions of PHE, PYR and FLU, and PHA production, using novel mixed bacterial cultures and modified repeated batch fermentation. The MCL-PHA formed had uniquely high 3-HD content.

Mycoremediation of Old and Intermediate Landfill Leachates with an Ascomycete Fungal Isolate, Lambertella sp

In the present study, an Ascomycete fungal strain, Lambertella sp., isolated from environmental polluted matrices, was tested for the capacity to reduce the contamination and the toxicity of intermediate and old landfill leachates. Batch tests in flasks, under co-metabolic conditions, were performed with two different old leachates, with suspended and immobilized Lambertella sp. biomass, resulting in a soluble chemical oxygen demand depletion of 70% and 45%, after 13 and 30 days, respectively. An intermediate landfill leachate was treated in lab-scale reactors operating in continuous conditions for three months, inoculated with immobilized Lambertella sp. biomass, in absence of co-substrates. The Lambertella sp. depleted the corresponding total organic carbon by 90.2%. The exploitability of the Lambertella sp. strain was evaluated also in terms of reduction of phyto-, cyto-, and mutagenicity of the different Landfill Leachates at the end of the myco-based treatment, resulting in an efficient depletion of leachate clastogenicity.

Use of a Zeolite and Molecular Sieve to Restore Homeostasis of Soil Contaminated with Cobalt

Since contamination of soil with cobalt disturbs the soil’s biological balance, various types of compounds are being sought that could be used to restore the homeostasis of contaminated soil. The aim of the study was to determine the use of a Bio.Zeo.S.01 zeolite and molecular sieve in restoring the microbiological and biochemical balance of soil contaminated with cobalt. Soil samples were contaminated with cobalt (CoCl2·6H2O) at 0, 20, 80 mg·kg−1, and a Bio.Zeo.S.01 zeolite and molecular sieve were introduced at 0 and 15 g·kg−1. The soils on which the experiment was conducted were loamy sand and sandy clay loam. The experiment was carried out in two series on soil with and without a crop sown in it. The multiplication of microorganisms and the soil enzymes’ activity were determined on days 25 and 50 (harvest) of the experiment, and the yield of the underground and above-ground parts of maize and chemical and physical properties of soil were determined on the day of harvest. It was found that the microorganisms’ multiplication, enzyme activity, and maize yield were significantly disturbed by the excess of cobalt in the soil regardless of the soil type. The zeolite Bio.Zeo.S.01 used in the study had a smaller impact on microorganisms and soil enzyme activity than the molecular sieve. Cobalt accumulated more in the roots than in the above-ground parts of maize. An addition of sorbents decreased the accumulation of cobalt in maize grown only on sandy clay loam.

Cross-Bioaugmentation Among Four Remote Soil Samples Contaminated With Oil Exerted Just Inconsistent Effects on Oil-Bioremediation

Soil samples were collected from Kuwait, Lebanon, Egypt, and Germany, and artificially polluted with 3% (w/w) crude oil. Cross-bioaugmentation was done among them, and the oil-consumption and the constituent communities of hydrocarbonoclastic bacteria were monitored periodically through 6 months. The results showed that cross-bioaugmentation did not bring about reproducible effects on oil-removal in the four soils. After 6 months, oil-removal values reached between 82 and 95% in most of the samples including the unbioaugmented controls. The numbers of hydrocarbonoclastic bacteria showed significant increases followed by significant decreases during the course of bioremediation also in the unbioaugmented controls. In most cases, the inoculated bacterial taxa failed to colonize the soils, and oil-removal was achieved mainly by the native (autochthonous) soil bacterial communities. those belonged to the genera Mycolicibacterium, Mycobacterium, Xanthobacter, Pseudoxanthomonas, Pseudomonas, Zavarzinia, and others. The microbial communities in the four soils also comprised nitrogen fixing bacteria belonging to the genera Gordonia, Rhizobium, Kocuria, and Azospirillum. Such diazotrophs are known to enrich the soils with fixed nitrogen and thus, contribute to enhancing the microbiological hydrocarbon-consumption. It was concluded that cross-bioaugmentation leads to unpredictable and inconsistent effects on oil removal. Therefore, it could not beregarded as the technology of choice for oil-bioremediation.

Pea cultivar Blauwschokker for the phytostimulation of biodiesel degradation in agricultural soil

Phytoremediation is a cost-effective and ecologically friendly process that involves the use of plants to uptake, accumulate, translocate, stabilize, or degrade pollutants. The present study was conducted to demonstrate the potential of pea (Pisum sativum L. spp. sativum) cultivar Blauwschokker to phytostimulate biodiesel degradation in an agricultural soil, considering the influence of biological remediation on selected physiological parameters of plants and the amount and activity of soil microflora. Biodiesel was spiked into soil in dose of 50 g kg-1 of dry mass soil. The results of the study showed that the rate of biodiesel degradation in the vegetated soil was higher than that occurring by natural attenuation. At the same time, biodiesel showed a positive effect on the growth, development, and activity of soil bacteria and fungi. Moreover, the obtained results showed an improvement in physiological parameters of plants, including an increase in chlorophyll a and total chlorophyll content and higher relative water content in leaves in the presence of biodiesel.

Bioremediation techniques-classification based on site of application: principles, advantages, limitations and prospects

Environmental pollution has been on the rise in the past few decades owing to increased human activities on energy reservoirs, unsafe agricultural practices and rapid industrialization. Amongst the pollutants that are of environmental and public health concerns due to their toxicities are: heavy metals, nuclear wastes, pesticides, green house gases, and hydrocarbons. Remediation of polluted sites using microbial process (bioremediation) has proven effective and reliable due to its eco-friendly features. Bioremediation can either be carried out ex situ or in situ, depending on several factors, which include but not limited to cost, site characteristics, type and concentration of pollutants. Generally, ex situ techniques apparently are more expensive compared to in situ techniques as a result of additional cost attributable to excavation. However, cost of on-site installation of equipment, and inability to effectively visualize and control the subsurface of polluted sites are of major concerns when carrying out in situ bioremediation. Therefore, choosing appropriate bioremediation technique, which will effectively reduce pollutant concentrations to an innocuous state, is crucial for a successful bioremediation project. Furthermore, the two major approaches to enhance bioremediation are biostimulation and bioaugmentation provided that environmental factors, which determine the success of bioremediation, are maintained at optimal range. This review provides more insight into the two major bioremediation techniques, their principles, advantages, limitations and prospects.

Exogenous IAA treatment enhances phytoremediation of soil contaminated with phenanthrene by promoting soil enzyme activity and increasing microbial biomass

In this study, we aimed to confirm that indole-3-acetic acid promotes plant uptake of phenanthrene (PHE), stimulates the activity of soil enzymes or microflora, and thereby accelerates the dissipation of PHE in soil. Four treatments were evaluated: PHE-contaminated soil planted with (1) ryegrass (T0), (2) ryegrass and supplemented with 1 mg kg(-1) indole-3-acetic acid (IAA) (T1), (3) ryegrass and supplemented with 5 mg kg(-1) IAA (T5), and (4) ryegrass and supplemented with 10 mg kg(-1) IAA (T10). After 30 days, PHE concentrations were lower for all treatments and the removal rate was 70.19, 89.17, 91.26, and 97.07 % for T0, T1, T5, and T10, respectively. PHE was only detected in the roots and not in the shoots. IAA facilitated the accumulation of PHE in the roots, and plants subjected to the T10 treatment had the highest levels. Exogenous IAA stimulated soil peroxidase activity in a dose-dependent manner, whereas soil polyphenoloxidase activity was not significantly increased, except in T10. Soil microbial biomass also increased in response to IAA treatment, particularly in T10. Furthermore, phospholipid fatty acid analysis showed that IAA treatment increased microbial biomass and alleviated environmental stress. Gram-positive bacteria are largely responsible for polycyclic aromatic hydrocarbon degradation, and we found that the ratio of gram-positive to gram-negative bacteria in the soil significantly increased as the IAA concentrations increased (P < 0.05). Correlation analysis indicated that the increase in soil microbial biomass, enzyme activity, and plant uptake of PHE promotes removal of PHE from the soil.

Isolation and characterization of a hydrocarbonoclastic bacterial enrichment from total petroleum hydrocarbon contaminated sediments: potential candidates for bioaugmentation in bio-based processes

Seven hydrocarbonoclastic new bacterial isolates were isolated from dredged sediments of a river estuary in Italy. The sediments were contaminated by shipyard activities since decades, mainly ascribable to the exploitation of diesel oil as the fuel for recreational and commercial navigation of watercrafts. The bacterial isolates were able to utilize diesel oil as sole carbon source. Their metabolic capacities were evaluated by GC-MS analysis, with reference to the depletion of both the normal and branched alkanes, the nC18 fatty acid methyl ester and the unresolved complex mixture of organic compounds. They were taxonomically identified as different species of Stenotrophomonas and Pseudomonas spp. by the combination of amplified ribosomal DNA restriction analysis (ARDRA) and repetitive sequence-based PCR (REP-PCR) analysis. The metabolic activities of interest were analyzed both in relation to the single bacterial strains and to the combination of the latter as a multibacterial species system. After 6 days of incubation in mineral medium with diesel oil as sole carbon source, the Stenotrophomonas sp. M1 strain depleted 43-46 % of Cn-alkane from C28 up to C30, 70 % of the nC18 fatty acid methyl ester and the 46 % of the unresolved complex mixture of organic compounds. On the other hand, the Pseudomonas sp. NM1 strain depleted the 76 % of the nC18 fatty acid methyl ester, the 50 % of the unresolved complex mixture of organic compounds. The bacterial multispecies system was able to completely deplete Cn-alkane from C28 up to C30 and to deplete the 95 % of the unresolved complex mixture of organic compounds. The isolates, either as single strains and as a bacterial multispecies system, were proposed as candidates for bioaugmentation in bio-based processes for the decontamination of dredged sediments.