Phytoremediation of metals from fly ash through bacterial augmentation

Fly ash toxicity, emerging issues and possible implications for its exploitation in agriculture; Indian scenario: A review

Fly ash is considered as an environmental hazard worldwide, since it generally contain organic pollutants, probable toxic metals like Se, As, B, V, Al, Pb, Hg, Cr and radionuclide's Uranium, Thorium. Although fly ash contains toxic substances, it also contains most of the oxides and trace elements. Presence of oxides contributes to its alkaline pH while trace elements provides nutrients for plant growth hence, it is suggested that it can be used in low concentration in agriculture sector as well as a soil conditioner as fly ash improves the physico-chemical and biological properties of contaminated soils. This article presents a review on causes of fly ash toxicities due to organic pollutants, heavy metals, radioactive elements and environmental issues related to its utilization and possibilities of fly ash exploitation in agriculture sector such as phytoremediation, bioremediation, reclamation of wasteland and forestry.

Biochemical interactions between Glycine max L. silicon dioxide (SiO2) and plant growth-promoting bacteria (PGPR) for improving phytoremediation of soil contaminated with fenamiphos and its degradation products

Fenamiphos is a systematic nematicide-insecticide used extensively for the control of soil nematodes. Fenamiphos and oxidation products have been known to induce water pollution, soil pollution and ecotoxicological effects on aquatic organisms, as well as heath issues. This contaminant can be removed by phytoremediation. Herein, we tested several strategies to improve the effectiveness of this technology. A combination of G. max plus Pseudomonas fluorescens was more efficient than G. max plus Serratia marcescens or G. max alone in degrading fenamiphos to other metabolites. Three major metabolites, namely fenamiphos sulfoxide (FSO), fenamiphos sulfone (FSO2) and fenamiphos phenol (F-phenol), were detected in roots and leaves in which G. max amended with P. fluorescens or amended with S. marcescens produced a significant accumulation of FSO and FSO2 with higher amounts than for G. max alone. Leaf concentrations of FSO were always higher than in the roots, while FSO2 accumulated significantly more in G. max roots than in G. max leaves. In soil treated with fenamiphos, G. max roots and leaves alone, and in combined effects of plant and microorganisms, resulted in the disappearance of fenamiphos and the appearance of F-SO, F-SO2 and F-phenol, which in turn caused toxic stress in G. max and the resulting production of reactive oxygen species such as H2O2 with higher content and an increase in antioxidant GPX activity. Although a batch equilibrium technique showed that use of SiO2 resulted in the efficient removal of fenamiphos when compared with other treatments for removing adsorbed fenamiphos from soil, a fewer amount of fenamiphos was removed by G. max L. with SiO2. H2O2 content and GPX activity increased in G. max under fenamiphos treatment and its degradation products, while amended G. max with SiO2 or Argal led to a decrease in GPX activity and H2O2 content.

Metal-resistant rhizobacteria isolates improve Mucuna deeringiana phytoextraction capacity in multi-metal contaminated soils from a gold mining area

Phytoremediation consists of biological techniques for heavy metal remediation, which include exploring the genetic package of vegetable species to remove heavy metals from the environment. The goals of this study were to investigate heavy metal and bioaugmentation effects on growth and nutrient uptake by Mucuna deeringiana; to determine the metal translocation factor and bioconcentration factor and provide insight for using native bacteria to enhance heavy metal accumulation. The experiment was conducted under greenhouse conditions using a 2 × 4 factorial scheme with highly and slightly contaminated soil samples and inoculating M. deeringiana with three highly lead (Pb⁺²)-resistant bacteria Kluyvera intermedia (Ki), Klebsiella oxytoca (Ko), and Citrobacter murliniae (Cm) isolated from the rhizosphere of native plants identified as Senecio brasiliensis (Spreng.) Less., Senecio leptolobus DC., and Baccharis trimera (Less) DC., respectively. The increased heavy metal concentrations in soil samples do not decrease the root dry mass of M. deeringiana, concerning the number and dry weight of nodules. The shoot dry mass is reduced by the increasing concentration of heavy metals in soil associated with Kluyvera intermedia and Klebsiella oxytoca bacteria. The number of nodules is affected by heavy metals associated with Citrobacter murliniae bacteria. The bacteria K. intermedia, C. murliniae, and K. oxytoca increase the lead and cadmium available in the soil and enhanced metal uptake by Mucuna deeringiana. The M. deeringiana specie has characteristics that make it hyperaccumulate copper and zinc. The translocation and bioconcentration factors for M. deeringiana characterize it as a promising candidate to phytostabilize multi-metal contaminated soils.

Accumulation and translocation of heavy metal by spontaneous plants growing on multi-metal-contaminated site in the Southeast of Rio Grande do Sul state, Brazil

In recent years, the number of cases of heavy metal contamination has increased worldwide, leading to reports on environmental pollution and human health problems. Phytoremediation can be potentially used to remove heavy metal from contaminated sites. This study determined heavy metal concentrations in the biomass of plant species growing on a multi-metal-contaminated site. Seven plant species and associated rhizospheric soil were collected and analyzed for heavy metal concentrations. While plant Cu, Zn, Cd, Ni, Pb, As, and Ba concentrations ranged from 8.8 to 21.1, 56.4 to 514.3, 0.24 to 2.14, 1.56 to 2.76, 67.8 to 188.2, 0.06 to 1.21, and 0.05 to 0.62 mg kg(-1), respectively, none of the plants was identified as hyperaccumulators. Those in the rhizospheric soil ranged from 10.5 to 49.1, 86.2 to 590.9, 0.32 to 2.0, 3.6 to 8.2, 19.1 to 232.5, 2.0 to 35.6, and 85.8 to 170.3 mg kg(-1), respectively. However, Zn, Cd, Pb, and As concentrations in the soil outside the rhizosphere zone were 499.0, 2.0, 631.0, and 48.0 mg kg(-1), respectively. Senecio brasiliensis was most effective in translocating Cu, Cd, and Ba. The most effective plant for translocating Zn and Pb was Baccharis trimera and, for element As, Dicranopteris nervosa and Hyptis brevipes. Heavy metal and metalloid levels in spontaneous plants greatly exceeded the upper limits for terrestrial plants growing in uncontaminated soil, demonstrating the higher uptake of heavy metal from soil by these plants. It is concluded that naturally occurring species have a potential for phytoremediation programs.

Effect of plant growth-promoting bacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) inoculation on oats in saline-alkali soil contaminated by petroleum to enhance phytoremediation

To investigate the effect of plant growth-promoting bacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) on phytoremediation in saline-alkali soil contaminated by petroleum, saline-alkali soil samples were artificially mixed with different amount of oil, 5 and 10 g/kg, respectively. Pot experiments with oat plants (Avena sativa) were conducted under greenhouse condition for 60 days. Plant biomass, physiological parameters in leaves, soil enzymes, and degradation rate of total petroleum hydrocarbon were measured. The result demonstrated that petroleum inhibited the growth of the plant; however, inoculation with PGPR in combination with AMF resulted in an increase in dry weight and stem height compared with noninoculated controls. Petroleum stress increased the accumulation of malondialdehyde (MDA) and free proline and the activities of the antioxidant enzyme such as superoxide dismutase, catalase, and peroxidase. Application of PGPR and AMF augmented the activities of three enzymes compared to their respective uninoculated controls, but decreased the MDA and free proline contents, indicating that PGPR and AMF could make the plants more tolerant to harmful hydrocarbon contaminants. It also improved the soil quality by increasing the activities of soil enzyme such as urease, sucrase, and dehydrogenase. In addition, the degradation rate of total petroleum hydrocarbon during treatment with PGPR and AMF in moderately contaminated soil reached a maximum of 49.73%. Therefore, we concluded the plants treated with a combination of PGPR and AMF had a high potential to contribute to remediation of saline-alkali soil contaminated with petroleum.

Cell physiology of the biotechnological relevant bacterium Bacillus pumilus-an omics-based approach

Members of the species Bacillus pumilus get more and more in focus of the biotechnological industry as potential new production strains. Based on exoproteome analysis, B. pumilus strain Jo2, possessing a high secretion capability, was chosen for an omics-based investigation. The proteome and metabolome of B. pumilus cells growing either in minimal or complex medium was analyzed. In total, 1542 proteins were identified in growing B. pumilus cells, among them 1182 cytosolic proteins, 297 membrane and lipoproteins and 63 secreted proteins. This accounts for about 43% of the 3616 proteins encoded in the B. pumilus Jo2 genome sequence. By using GC-MS, IP-LC/MS and H NMR methods numerous metabolites were analyzed and assigned to reconstructed metabolic pathways. In the genome sequence a functional secretion system including the components of the Sec- and Tat-secretion machinery was found. Analysis of the exoproteome revealed secretion of about 70 proteins with predicted secretion signals. In addition, selected production-relevant genome features such as restriction modification systems and NRPS clusters of B. pumilus Jo2 are discussed.

Effect of PGPR Serratia marcescens BC-3 and AMF Glomus intraradices on phytoremediation of petroleum contaminated soil

Soil contamination caused by petroleum hydrocarbons has become a worldwide environmental problem. Microorganism combined with phytoremediation appears to be more effective for removal and/or degradation of petroleum hydrocarbons from impacted soils. The current study investigated the effect of inoculated with PGPR Serratia marcescens BC-3 alone or in combination with AMF Glomus intraradices on the phytoremediation of petroleum-contaminated soil. Pot experiments were conducted to analyze the effect on plant and soil for 90 days in greenhouse. The inoculation treatments showed higher plant biomass and antioxidant enzyme activities than the non inoculation control. Inoculation treatments also improved rhizosphere microbial populations in petroleum contaminated soil. The degradation rate of total petroleum hydrocarbons with PGPR and AMP co-inoculation treatment was up to 72.24 %. The results indicated that plant combined with microorganisms for remediation of petroleum hydrocarbons would be a feasible method.