Bioremediation of a Chilean Andisol contaminated with pentachlorophenol (PCP) by solid substrate cultures of white-rot fungi

Use of Anthracophyllum Discolor and Stereum Hirsutum as a Suitable Strategy for Delignification and Phenolic Removal of Olive Mill Solid Waste

This study evaluated the use of the white-rot fungi (WRF) Anthracophyllum discolor and Stereum hirsutum as a biological pretreatment for olive mill solid mill waste (OMSW). The WRF strains proposed were added directly to OMSW. The assays consisted of determining the need to add supplementary nutrients, an exogenous carbon source or use agitation systems, and evaluating WRF growth, enzyme activity, phenolic compound removal and lignin degradation. The highest ligninolytic enzyme activity was found at day 10, reaching 176.7 U/L of manganese-independent peroxidase (MniP) produced by A. discolor, and the highest phenolic removal (more than 80% with both strains) was reached after 24 days of incubation. The confocal laser scanning microscopy analysis (CLSM) confirmed lignin degradation through the drop in lignin relative fluorescence units (RFU) from 3967 for untreated OMSW to 235 and 221 RFU, showing a lignin relative degradation of 94.1% and 94.4% after 24 days of treatment by A. discolor and S. hirsutum, respectively. The results demonstrate for the first time that A. discolor and S. hirsutum were able to degrade lignin and remove phenolic compounds from OMSW using this as the sole substrate without adding other nutrients or using agitation systems. This work indicates that it could be possible to design an in situ pretreatment of the valorization of OMSW, avoiding complex systems or transportation. In this sense, future research under non-sterile conditions is needed to evaluate the competition of WRF with other microorganisms present in the OMSW. The main drawbacks of this work are associated with both the low reaction time and the water addition. However, OMSW is seasonal waste produced in one season per year, being stored for a long time. In terms of water addition, the necessary optimization will be addressed in future research.

Soil Redox Controls CO2, CH4 and N2O Efflux from White-Rot Fungi in Temperate Forest Ecosystems

Microaerophilic white-rot fungi (WRF) are impacted by oxygen depletion because of fluctuating redox occurrence in southern temperate forest soils of Chile (1500-5000 mm year^-1). How these conditions influence WRF survival has been scarcely examined. We explored the contributions of WRF to greenhouse gas (GHG) emissions of N₂O and CH₄ and soil organic C oxidation (CO₂) in five sterilized and inoculated forest soils derived from various parent materials and climates. The soil was incubated for 20 days following (i) oxic, (ii) anoxic, and (iii) fluctuating redox conditions. Fungi contributed to 45% of the total GHG under redox fluctuating conditions, including the contribution of bacteria, while the opposite (26%) was valid for oxic treatment. On average, the highest gas emission (62%) was N₂O for WRF under redox treatment, followed by anoxic (22%) and oxic (16%) treatments, while CO₂ and CH₄ emissions followed oxic > redox > anoxic. These data suggest that indigenous microbial WRF communities are well adapted to fluctuating redox milieu with a significant release of GHG emissions in humid temperate forests of the southern cone.

Dioxin impacts on lipid metabolism of soil microbes: towards effective detection and bioassessment strategies

Dioxins are the most toxic known environmental pollutants and are mainly formed by human activities. Due to their structural stability, dioxins persist for extended periods and can be transported over long distances from their emission sources. Thus, dioxins can be accumulated to considerable levels in both human and animal food chains. Along with sediments, soils are considered the most important reservoirs of dioxins. Soil microorganisms are therefore highly exposed to dioxins, leading to a range of biological responses that can impact the diversity, genetics and functional of such microbial communities. Dioxins are very hydrophobic with a high affinity to lipidic macromolecules in exposed organisms, including microbes. This review summarizes the genetic, molecular and biochemical impacts of dioxins on the lipid metabolism of soil microbial communities and especially examines modifications in the composition and architecture of cell membranes. This will provide a useful scientific benchmark for future attempts at soil ecological risk assessment, as well as in identifying potential dioxin-specific-responsive lipid biomarkers. Finally, potential uses of lipid-sequestering microorganisms as a part of biotechnological approaches to the bio-management of environmental contamination with dioxins are discussed.

White rot fungus Pleurotus pulmonarius enhanced bioremediation of highly PCDD/F-contaminated field soil via solid state fermentation

This study was performed to evaluate the use of white rot fungus, Pleurotus pulmonarius, to treat polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) in contaminated soil using solid state fermentation (SSF). The soil was collected from a long-closed pentachlorophenol plant in southern Taiwan. The non-sterilized soil with a total PCDD/F concentration of 14,000 ± 2400 ng I-TEQ kg^-1 was mixed directly with the solid fungal inocula at dry w/w ratio of 1:1.4 (ratio-adjusted test) and incubated at 26 ± 2 °C in a controlled environment. The highest PCDD/F decomposition was observed during the mycelium colonization. Pearson correlation coefficient (r) studied during this period (35 days) indicated that laccase had no significant correlation (r = -0.53), while manganese peroxidase had a strong positive correlation (r = 0.88) with PCDD/F decomposition efficiency. After 72 days, the more toxic congeners, tetra- and penta-CDD/Fs were removed to non-detectable levels. Meanwhile, the removal efficiencies of hexa-, hepta-, and octa-CDD/Fs were >80%, >97%, and >90%, respectively. The simultaneous degradation of low and high chlorinated DD/Fs suggested that overall removal was nonspecific. The overall PCDD/F removal was 96%, and the residual concentration (276 ng I-TEQ kg^-1) was below the regulatory control limit (1000 ng I-TEQ kg^-1). In conclusion, this study shows that P. pulmonarius via SSF can successfully remediate the PCDD/F-contaminated field soil. Furthermore, this SSF technique overcame the well-known intractability of PCDD/F biodegradation in non-sterilized soil, making it promising for actual field application.

A proposed stepwise screening framework for the selection of polycyclic aromatic hydrocarbon (PAH)-degrading white rot fungi

This study suggests a simple three-step screening protocol for the selection of white rot fungi (WRF) capable of degrading polycyclic aromatic hydrocarbons (PAHs), which combines easily applicable bioassay techniques, and verifies that protocol by evaluating the PAH degradation activity, ligninolytic enzyme secretion, and relevant gene expressions of the selected PAH-degraders. Using 120 fungal strains, a sequence of bioassay techniques was applied: Bavendamm's reaction (Step 1), remazol brilliant blue R (RBBR) decolorization (Step 2); assays for tolerance to four mixed PAHs-phenanthrene, anthracene, fluoranthene, and pyrene (Step 3). This stepwise protocol selected 14 PAH-degrading WRF, including Microporus vernicipes, Peniophora incarnata, Perenniporia subacida, Phanerochaete sordida, Phlebia acerina, and Phlebia radiata. Of these, P. incarnata exhibited the highest PAH degradative activity, ranging from 40 to > 90%, which was related to the time-variable secretions of three extracellular ligninolytic enzymes: laccase, manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP). Laccase and MnP production by P. incarnata tended to be greater in the early stages of PAH degradation, whereas its LiP production became intensified with decreasing laccase and MnP production. Pilc1 and pimp1 genes encoding laccase and MnP were expressed, indicating the occurrence of extracellular enzyme-driven biodegradation of PAH by the fungal strains.

Development of hybrid processes for the removal of volatile organic compounds, plasticizer, and pharmaceutically active compound using sewage sludge, waste scrap tires, and wood chips as sorbents and microbial immobilization matrices

This study evaluated the reutilization of waste materials (scrap tires, sewage sludge, and wood chips) to remove volatile organic compounds (VOCs) benzene/toluene/ethylbenzene/xylenes/trichloroethylene/cis-1,2-dichloroethylene (BTEX/TCE/cis-DCE), plasticizer di(2-ethylhexyl) phthalate (DEHP), and pharmaceutically active compound carbamazepine from artificially contaminated water. Different hybrid removal processes were developed: (1) 300 mg/L BTEX + 20 mg/L TCE + 10 mg/L cis-DCE + tires + Pseudomonas sp.; (2) 250 mg/L toluene + sewage sludge biochar + Pseudomonas sp.; (3) 100 mg/L DEHP + tires + Acinetobacter sp.; and (4) 20 mg/L carbamazepine + wood chips + Phanerochaete chrysosporium. For the hybrid process (1), the removal of xylenes, TCE, and cis-DCE was enhanced, resulted from the contribution of both physical adsorption and biological immobilization removal. The hybrid process (2) was also superior for the removal of DEHP and required a shorter time (2 days) for the bioremoval. For the process (3), the biochar promoted the microbial immobilization on its surface and substantially enhanced/speed up the bioremoval of toluene. The fungal immobilization on wood chips in the hybrid process (4) also improved the carbamazepine removal considerably (removal efficiencies of 61.3 ± 0.6%) compared to the suspended system without wood chips (removal efficiencies of 34.4 ± 1.8%). These hybrid processes would not only be promising for the bioremediation of environmentally concerned contaminants but also reutilize waste materials as sorbents without any further treatment.

Synergistic plant-microbes interactions in the rhizosphere: a potential headway for the remediation of hydrocarbon polluted soils

Soil pollution is an unavoidable evil; many crude-oil exploring communities have been identified to be the most ecologically impacted regions around the world due to hydrocarbon pollution and their concurrent health risks. Several clean-up technologies have been reported on the removal of hydrocarbons in polluted soils but most of them are either very expensive, require the integration of advanced mechanization and/or cannot be implemented in small scale. However, "Bioremediation" has been reported as an efficient, cost-effective and environment-friendly technology for clean-up of hydrocarbon"s contaminated soils. Here, we suggest the implementation of synergistic mechanism of bioremediation such as the use of rhizosphere mechanism which involves the actions of plant and microorganisms, which involves the exploitation of plant and microorganisms for effective and speedy remediation of hydrocarbon"s contaminated soils. In this mechanism, plant"s action is synergized with the soil microorganisms through the root rhizosphere to promote soil remediation. The microorganisms benefit from the root metabolites (exudates) and the plant in turn benefits from the microbial recycling/solubilizing of mineral nutrients. Harnessing the abilities of plants and microorganisms is a potential headway for cost-effective clean-up of hydrocarbon"s polluted sites; such technology could be very important in countries with great oil producing activities/records over many years but still developing.

Pyrene and Chrysene Tolerance and Biodegradation Capability of Pleurotus Sajor-Caju

Introduction:

The present work focused on the biodegradation capability of a white-rot fungus, the Pleurotus sajor-caju, when exposed to polycyclic aromatic hydrocarbons.

Methods:

The research was carried out by using in vitro systems developed on Petri dishes, to evaluate the fungal tolerance to pyrene and chrysene, followed by experiments in liquid medium. The first experimental campaign was necessary to evaluate the conditions promoting fungal growth and tolerance (presence of surfactants, peptone, copper sulphate and lecithin) and it was designed and analysed using statistical techniques.

Results:

It was found that the fungal population growth is strongly inhibited by chrysene presence. On the other hand, pyrene had a mild negative impact on the mycelia growth, which seemed to be positively influenced by the presence of Tween 80 and copper sulphate. Starting from these results, the behaviour of Pleurotus sajor-caju in presence of pyrene was investigated in liquid medium. Results showed that the depletion of pyrene was evident during a period of 20 days, and removal efficiency was greater than 90%.

The role of sorption processes in the removal of pharmaceuticals by fungal treatment of wastewater

The contribution of the sorption processes in the elimination of pharmaceuticals (PhACs) during the fungal treatment of wastewater has been evaluated in this work. The sorption of four PhACs (carbamazepine, diclofenac, iopromide and venlafaxine) by 6 different fungi was first evaluated in batch experiments. Concentrations of PhACs in both liquid and solid (biomass) matrices from the fungal treatment were measured. Contribution of the sorption to the total removal of pollutants ranged between 3% and 13% in relation to the initial amount. The sorption of 47 PhACs in fungi was also evaluated in a fungal treatment performed in 26days in a continuous bioreactor treating wastewater from a veterinary hospital. PhACs levels measured in the fungal biomass were similar to those detected in conventional wastewater treatment (WWTP) sludge. This may suggest the necessity of manage fungal biomass as waste in the same manner that the WWTP sludge is managed.

Immobilization of the white-rot fungus Anthracophyllum discolor to degrade the herbicide atrazine

Herbicides cause environmental concerns because they are toxic and accumulate in the environment, food products and water supplies. There is a need to develop safe, efficient and economical methods to remove them from the environment, often by biodegradation. Atrazine is such herbicide. White-rot fungi have the ability to degrade herbicides of potential utility. This study formulated a novel pelletized support to immobilize the white-rot fungus Anthracophyllum discolor to improve its capability to degrade the atrazine using a biopurification system (BS). Different proportions of sawdust, starch, corn meal and flaxseed were used to generate three pelletized supports (F1, F2 and F3). In addition, immobilization with coated and uncoated pelletized supports (CPS and UPS, respectively) was assessed. UPS-F1 was determined as the most effective system as it provided high level of manganese peroxidase activity and fungal viability. The half-life (t_1/2) of atrazine decreased from 14 to 6 days for the control and inoculated samples respectively. Inoculation with immobilized A. discolor produced an increase in the fungal taxa assessed by DGGE and on phenoloxidase activity determined. The treatment improves atrazine degradation and reduces migration to surface and groundwater.

Depletion of pentachlorophenol in soil microcosms with Byssochlamys nivea and Scopulariopsis brumptii as detoxification agents

Pentachlorophenol (PCP) is a toxic compound which is widely used as a wood preservative product and general biocide. It is persistent in the environment and has been classified as a persistent organic pollutant to be reclaimed in many countries. Fungal bioremediation is an emerging approach to rehabilitating areas fouled by recalcitrant xenobiotics. In the present study, we isolated two fungal strains from an artificially PCP-contaminated soil during a long-term bioremediation study and evaluated their potential as bioremediation agents in depletion and detoxification of PCP in soil microcosms. The two fungal strains were identified as: Byssochlamys nivea (Westling, 1909) and Scopulariopsis brumptii (Salvanet-Duval, 1935). PCP removal and toxicity were examined during 28 days of incubation. Bioaugmented microcosms revealed a 60% and 62% PCP removal by B. nivea and S. brumptii, respectively. Co-inoculation of B. nivea and S. brumptii showed a synergetic effect on PCP removal resulting in 95% and 80% PCP decrease when initial concentrations were 12.5 and 25 mg kg^-1, respectively. Detoxification in bioaugmented soil and the efficient role of fungi in the rehabilitation of PCP contaminated soil were experimentally proven by toxicity assays. A decrease in inhibition of bioluminescence of Escherichia coli HB101 pUCD607 and an increase of germination index of mustard (Brassica alba) seeds were observed in the decontaminated soils.

The impact on the soil microbial community and enzyme activity of two earthworm species during the bioremediation of pentachlorophenol-contaminated soils

The ecological effect of earthworms on the fate of soil pentachlorophenol (PCP) differs with species. This study addressed the roles and mechanisms by which two earthworm species (epigeic Eisenia fetida and endogeic Amynthas robustus E. Perrier) affect the soil microbial community and enzyme activity during the bioremediation of PCP-contaminated soils. A. robustus removed more soil PCP than did E. foetida. A. robustus improved nitrogen utilisation efficiency and soil oxidation more than did E. foetida, whereas the latter promoted the organic matter cycle in the soil. Both earthworm species significantly increased the amount of cultivable bacteria and actinomyces in soils, enhancing the utilisation rate of the carbon source (i.e. carbohydrates, carboxyl acids, and amino acids) and improving the richness and evenness of the soil microbial community. Additionally, earthworm treatment optimized the soil microbial community and increased the amount of the PCP-4-monooxygenase gene. Phylogenic classification revealed stimulation of indigenous PCP bacterial degraders, as assigned to the families Flavobacteriaceae, Pseudomonadaceae and Sphingobacteriacea, by both earthworms. A. robustus and E. foetida specifically promoted Comamonadaceae and Moraxellaceae PCP degraders, respectively.

Evaluation of the potential of soil remediation by direct multi-channel pulsed corona discharge in soil

A novel approach, named multi-channel pulsed corona discharge in soil, was developed for remediating organic pollutants contaminated soil, with p-nitrophenol (PNP) as the model pollutant. The feasibility of PNP degradation in soil was explored by evaluating effects of pulse discharge voltage, air flow rate and soil moisture on PNP degradation. Based on roles of chemically active species and evolution of degradation intermediates, PNP degradation processes were discussed. Experimental results showed that about 89.4% of PNP was smoothly degraded within 60min of discharge treatment at pulse discharge voltage 27kV, soil moisture 5% and air flow rate 0.8Lmin(-1), and the degradation process fitted the first-order kinetic model. Increasing pulse discharge voltage was found to be favorable for PNP degradation, but not for energy yield. There existed appropriate air flow rate and soil moisture for obtaining gratifying PNP degradation efficacy. Roles of radical scavenger and measurement of active species suggested that ozone, H2O2, and OH radicals played very important roles in PNP degradation. CN bond in PNP molecule was cleaved, and the main intermediate products such as hydroquinone, benzoquinone, catechol, phenol, acetic acid, formic acid, oxalic acid, NO2(-) and NO3(-) were identified. Possible pathway of PNP degradation in soil in such a system was proposed.

Involvement of cytochrome P450 in pentachlorophenol transformation in a white rot fungus Phanerochaete chrysosporium

The occurrence of cytochrome P450 and P450-mediated pentachlorophenol oxidation in a white rot fungus Phanerochaete chrysosporium was demonstrated in this study. The carbon monoxide difference spectra indicated induction of P450 (103±13 pmol P450 per mg protein in the microsomal fraction) by pentachlorophenol. The pentachlorophenol oxidation by the microsomal P450 was NADPH-dependent at a rate of 19.0±1.2 pmol min⁻¹ (mg protein)⁻¹, which led to formation of tetrachlorohydroquinone and was significantly inhibited by piperonyl butoxide (a P450 inhibitor). Tetrachlorohydroquinone was also found in the cultures, while the extracellular ligninases which were reported to be involved in tetrachlorohydroquinone formation were undetectable. The formation of tetrachlorohydroquinone was not detectable in the cultures added with either piperonyl butoxide or cycloheximide (an inhibitor of de novo protein synthesis). These results revealed the pentachlorophenol oxidation by induced P450 in the fungus, and it should be the first time that P450-mediated pentachlorophenol oxidation was demonstrated in a microorganism. Furthermore, the addition of the P450 inhibitor to the cultures led to obvious increase of pentachlorophenol, suggesting that the relationship between P450 and pentachlorophenol methylation is worthy of further research.

Degradation of polycyclic aromatic hydrocarbons by the Chilean white-rot fungus Anthracophyllum discolor

The degradation of three- and four-ring polycyclic aromatic hydrocarbons (PAHs) in Kirk medium by Anthracophyllum discolor, a white-rot fungus isolated from the forest of southern Chile, was evaluated. In addition, the removal efficiency of three-, four- and five-ring PAHs in contaminated soil bioaugmented with A. discolor in the absence and presence of indigenous soil microorganisms was investigated. Production of lignin-degrading enzymes and PAH mineralization in the soil were also determined. A. discolor was able to degrade PAHs in Kirk medium with the highest removal occurring in a PAH mixture, suggesting synergistic effects between PAHs or possible cometabolism. A high removal capability for phenanthrene (62%), anthracene (73%), fluoranthene (54%), pyrene (60%) and benzo(a)pyrene (75%) was observed in autoclaved soil inoculated with A. discolor in the absence of indigenous microorganisms, associated with the production of manganese peroxidase (MnP). The metabolites found in the PAH degradation were anthraquinone, phthalic acid, 4-hydroxy-9-fluorenone, 9-fluorenone and 4,5-dihydropyrene. A. discolor was able to mineralize 9% of the phenanthrene. In non-autoclaved soil, the inoculation with A. discolor did not improve the removal efficiency of PAHs. Suitable conditions must be found to promote a successful fungal bioaugmentation in non-autoclaved soils.