Indigenous fungi with the ability to biodegrade hydrocarbons in diesel-contaminated soil are isolated and selected using a simple methodology.

Soil contamination by hydrocarbons is a problem that causes severe damage to the environment and public health. Technologies such as bioremediation using native microbial species represent a promising and environmentally friendly alternative for decontamination. This study aimed to isolate indigenous fungi species from the State of Rio de Janeiro, Brazil and evaluate their diesel degrading capacity in soils contaminated with crude oil. Seven filamentous fungi were isolated after enrichment cultivation from soils collected from contaminated sites and subjected to growth analysis on diesel nutrient media. Two fungal species were pre-selected and identified by morphological genus analysis and molecular techniques as Trichoderma asperellum and Penicillium pedernalense. The microdilution test showed that T. asperellum presented better fungal growth in high diesel concentrations than P. pedernalense. In addition, T. asperellum was able to degrade 41 and 54% of the total petroleum hydrocarbon (TPH) content present in soil artificially contaminated with diesel (10 g/kg of soil) in 7 and 14 days of incubation, respectively. In higher diesel concentration (1000 g of diesel/kg of soil) the TPH degradation reached 26%, 45%, and 48%, in 9, 16, and 30 d, respectively. The results demonstrated that the selected species was suitable for diesel degradation. We can also conclude that the isolation and selection process proposed in this work was successful and represents a simple alternative for obtaining native species with hydrocarbon degradation capacity, for use in the bioremediation process in the recovery of contaminated areas in an ecologically acceptable way.

Shifts in structure and dynamics of the soil microbiome in biofuel/fuel blend-affected areas triggered by different bioremediation treatments.

The use of biofuels has grown in the last decades as a consequence of the direct environmental impacts of fossil fuel use. Elucidating structure, diversity, species interactions, and assembly mechanisms of microbiomes is crucial for understanding the influence of environmental disturbances. However, little is known about how contamination with biofuel/petrofuel blends alters the soil microbiome. Here, we studied the dynamics in the soil microbiome structure and composition of four field areas under long-term contamination with biofuel/fossil fuel blends (ethanol 10% and gasoline 90%-E10; ethanol 25% and gasoline 75%-E25; soybean biodiesel 20% and diesel 80%-B20) submitted to different bioremediation treatments along a temporal gradient. Soil microbiomes from biodiesel-polluted areas exhibited higher richness and diversity index values and more complex microbial communities than ethanol-polluted areas. Additionally, monitored natural attenuation B20-polluted areas were less affected by perturbations caused by bioremediation treatments. As a consequence, once biostimulation was applied, the degradation was slower compared with areas previously actively treated. In soils with low diversity and richness, the impact of bioremediation treatments on the microbiomes was greater, and as a result, the hydrocarbon degradation extent was higher. The network analysis showed that all abundant keystone taxa corresponded to well-known degraders, suggesting that the abundant species are core targets for biostimulation in soil remediation processes. Altogether, these findings showed that the knowledge gained through the study of microbiomes in contaminated areas may help design and conduct optimized bioremediation approaches, paving the way for future rationalized and efficient pollutant mitigation strategies.

Efficient bioremediation of indigo-dye contaminated textile wastewater using native microorganisms and combined bioaugmentation-biostimulation techniques.

In this work, the bioremediation of wastewater from the textile industry with indigo dye content was carried out using combined bioaugmentation, bioventilation, and biostimulation techniques. Initially, the inoculum was prepared by isolating the microorganisms from the textile wastewater in a 2 L bioreactor. Then, the respirometry technique was implemented to determine the affinity of the microorganisms and the substrate by measuring CO2 and allowed the formulation of an empirical mathematical model for the growth kinetics of the microorganism. Finally, the bioremediation was carried out in a 3 L bioreactor obtaining an indigo dye removal efficiency of 20.7 ± 1.2%, 24.0 ± 1.5%, and 29.7 ± 1.1% for equivalent wavelengths of 436 nm, 525 nm, and 620 nm. The chemical oxygen demand showed an average reduction of 88.9 ± 2.5%, going from 470.7 ± 15.6 to 52.3 ± 10.7 ppm after 30 days under constant agitation and aeration. A negative generalized exponential model was fitted to assess the affinity of the microorganism with the wastewater as a substrate by evaluating the production of CO2 during the bioremediation. Bioremediation techniques improve water discharge parameters compared to chemical treatments implemented in the industry, reducing the use of substances that can generate secondary pollution. Bioaugmentation, biostimulation, and bioventing of the textile wastewater in this study demonstrate the potential of these combined techniques to serve as an efficient alternative for indigo-contaminated wastewater in the textile industry.

Bioremediation of an industrial soil contaminated by hydrocarbons in microcosm system, involving bioprocesses utilizing co-products and agro-industrial wastes.

The present study describes practical implication of bioaugmentation and biostimulation processes for bioremediation of an industrial soil chronically contaminated by hydrocarbons. For this purpose, biomass production of six autochthonous hydrocarbon-degrading bacteria were evaluated as inoculum of bioaugmentation strategy, by testing carbon and nitrogen sources included co-products and agro-industrial waste as sustainable and low-cost components of the growth medium. Otherwise, biostimulation was approached by the addition of optimized concentration of nitrogen and phosphorus. Microcosm assays showed that total hydrocarbons (TH) were significantly removed from chronically contaminated soil undergoing bioremediation treatment. Systems Mix (bioaugmentation); N,P (biostimulation) and Mix + N,P (bioaugmentation and biostimulation) reached higher TH removal, being 89.85%, 91.00%, 93.04%, respectively, comparing to 77.83% of system C (natural attenuation) at 90 days. The increased heterotrophic aerobic bacteria and hydrocarbon degrading bacteria counts were according to TH biodegrading process during the experiments. Our results showed that biostimulation with nutrients represent a valuable alternative tool to treat a chronically hydrocarbon-contaminated industrial soil, while bioaugmentation with a consortium of hydrocarbon degrading bacteria would be justified when the soil has a low amount of endogenous degrading microorganisms. Furthermore, the production of inoculum for application in bioaugmentation using low-cost substrates, such as industrial waste, would lead to the development of an environmentally friendly and attractive process in terms of cost-benefit.

A comprehensive study on diesel oil bioremediation under microcosm conditions using a combined microbiological, enzymatic, mass spectrometry, and metabarcoding approach.

This study aims at the application of a marine fungal consortium (Aspergillus sclerotiorum CRM 348 and Cryptococcus laurentii CRM 707) for the bioremediation of diesel oil-contaminated soil under microcosm conditions. The impact of biostimulation (BS) and/or bioaugmentation (BA) treatments on diesel-oil biodegradation, soil quality, and the structure of the microbial community were studied. The use of the fungal consortium together with nutrients (BA/BS) resulted in a TPH (Total Petroleum Hydrocarbon) degradation 42% higher than that obtained by natural attenuation (NA) within 120 days. For the same period, a 72 to 92% removal of short-chain alkanes (C12 to C19) was obtained by BA/BS, while only 3 to 65% removal was achieved by NA. BA/BS also showed high degradation efficiency of long-chain alkanes (C20 to C24) at 120 days, reaching 90 and 92% of degradation of icosane and heneicosane, respectively. In contrast, an increase in the levels of cyclosiloxanes (characterized as bacterial bioemulsifiers and biosurfactants) was observed in the soil treated by the consortium. Conversely, the NA presented a maximum of 37% of degradation of these alkane fractions. The 5-ringed PAH benzo(a)pyrene, was removed significantly better with the BA/BS treatment than with the NA (48 vs. 38 % of biodegradation, respectively). Metabarcoding analysis revealed that BA/BS caused a decrease in the soil microbial diversity with a concomitant increase in the abundance of specific microbial groups, including hydrocarbon-degrading (bacteria and fungi) and also an enhancement in soil microbial activity. Our results highlight the great potential of this consortium for soil treatment after diesel spills, as well as the relevance of the massive sequencing, enzymatic, microbiological and GC-HRMS analyses for a better understanding of diesel bioremediation.

Monitoring of a microbial community during bioaugmentation with hydrogenotrophic methanogens to improve methane yield of an anaerobic digestion process.

Methane production by microbial fermentation of municipal waste is a challenge for better yield processes. This work describes the characterization of a hydrogenotrophic methanogen microbial community used in a bioaugmentation procedure to improve the methane yield in a thermophilic anaerobic process, digesting the organic fraction of municipal solid waste. The performance of the bioaugmentation was assessed in terms of methane production and changes in the microbial community structure. The results showed that bioaugmentation slightly improved the cumulative methane yield (+ 4%) in comparison to the control, and its use led to an acceleration of the methanogenesis stage. We observed associated significant changes in the relative abundance of taxa and their interactions, using high throughput DNA sequencing of V3-16S rRNA gene libraries, where the abundance of the archaeal hydrogenotrophic genus Methanoculleus (class Methanomicrobia, phylum Euryarchaeota) and the bacterial order MBA08 (class Clostridia, phylum Firmicutes) were dominant. The relevant predicted metabolic pathways agreed with substrate degradation and the anaerobic methanogenic process. The purpose of the study was to evaluate the effect of the addition of hydrogenotrophic methanogens in the generation of methane, while treating organic waste through anaerobic digestion.

Sequential application of activated sludge and phytoremediation with aquatic macrophytes on tannery effluents: in search of a complete treatment.

Tannery effluents with a high organic matter load (indicated by their COD level) have to be treated before they are discharged, so as to minimize their negative impact on the environment. Using field mesocosm systems, this study evaluated the feasibility of treating such effluents through bioaugmentation with activated sludge, followed by phytoremediation with aquatic macrophytes (Lemnoideae subfamily). Regardless of its quality, the activated sludge was able to remove approximately 77% of the COD from effluents with a low initial organic load (up to 1500 mg/L). The macrophytes then enhanced removal (up to 86%), so the final COD values were permissible under the current legislation for effluent discharge. When the initial organic load in the undiluted effluents was higher (around 3000 mg/L), the COD values obtained after consecutive bioaugmentation and phytoremediation were close to the legally allowed limits (583 mg/L), which highlights the potential of phytoremediation as a tertiary treatment. This treatment also brought total coliform counts down to legally acceptable values, without plant biomass decreasing over time. Moreover, the plant biomass remained viable and capable of high COD removal efficiency (around 75%) throughout two additional reuse cycles. These findings indicate that the efficiency of the biological treatments assayed here depends largely on the initial organic load in the tannery effluents. In any case, the sequential application of activated sludge and aquatic macrophytes proved to be a successful alternative for remediation.

Endophytic, extremophilic and entomophilic fungi strains biodegrade anthracene showing potential for bioremediation.

Anthropogenic activities have been increasing Polycyclic Aromatic Hydrocarbons (PAHs) release, promoting an urgent need for decontamination methods. Therefore, anthracene biodegradation by endophytic, extremophilic, and entomophilic fungi was studied. Moreover, a salting-out extraction methodology with the renewable solvent ethanol and the innocuous salt K2HPO4 was employed. Nine of the ten employed strains biodegraded anthracene in liquid medium (19-56% biodegradation) after 14 days at 30 °C, 130 rpm, and 100 mg L-1. The most efficient strain Didymellaceae sp. LaBioMMi 155, an entomophilic strain, was employed for optimized biodegradation, aiming at a better understanding of how factors like pollutant initial concentration, pH, and temperature affected this process. Biodegradation reached 90 ± 11% at 22 °C, pH 9.0, and 50 mg L-1. Futhermore, 8 different PAHs were biodegraded and metabolites were identified. Then, experiments with anthracene in soil ex situ were performed and bioaugmentation with Didymellaceae sp. LaBioMMi 155 presented better results than natural attenuation by the native microbiome and biostimulation by the addition of liquid nutrient medium into soil. Therefore, an expanded knowledge about PAHs biodegradation processes was achieved with emphasis to the action of Didymellaceae sp. LaBioMMi 155, which can be further employed for in situ biodegradation (after strain security test), or for enzyme identification and isolation aiming at oxygenases with optimal activity under alkaline conditions.

Metaproteomic and gene expression analysis of interspecies interactions in a PAH-degrading synthetic microbial consortium constructed with the key microbes of a natural consortium.

Polycyclic Aromatic Hydrocarbons (PAHs) impose adverse effects on the environment and human life. The use of synthetic microbial consortia is promising in bioremediation of contaminated sites with these pollutants. However, the design of consortia taking advantage of natural interactions has been poorly explored. In this study, a dual synthetic bacterial consortium (DSC_AB) was constructed with two key members (Sphingobium sp. AM and Burkholderia sp. Bk), of a natural PAH degrading consortium. DSC_AB showed significantly enhanced degradation of PAHs and toxic intermediary metabolites relative to the axenic cultures, indicating the existence of synergistic relationships. Metaproteomic and gene-expression analyses were applied to obtain a view of bacterial performance during phenanthrene removal. Overexpression of the Bk genes, naph, biph, tol and sal and the AM gene, ahdB, in DSC_AB relative to axenic cultures, demonstrated that both strains are actively participating in degradation, which gave evidence of cross-feeding. Several proteins related to stress response were under-expressed in DSC_AB relative to axenic cultures, indicating that the division of labour reduces cellular stress, increasing the efficiency of degradation. This is the one of the first works revealing bacterial relationships during PAH removal in a synthetic consortium applying an omics approach. Our findings could be used to develop criteria for evaluating the potential effectiveness of synthetic bacterial consortia in bioremediation.

Bioremediation of heavy oily sludge: a microcosms study.

Oily sludge is a residue from the petroleum industry composed of a mixture of sand, water, metals, and high content of hydrocarbons (HCs). The heavy oily sludge used in this study originated from Colombian crude oil with high density and low American Petroleum Institute (API) gravity. The residual waste from heavy oil processing was subject to thermal and centrifugal extraction, resulting in heavy oily sludge with very high density and viscosity. Biodegradation of the total petroleum hydrocarbons (TPH) was tested in microcosms using several bioremediation approaches, including: biostimulation with bulking agents and nutrients, the surfactant Tween 80, and bioaugmentation. Select HC degrading bacteria were isolated based on their ability to grow and produce clear zones on different HCs. Degradation of TPH in the microcosms was monitored gravimetrically and with gas chromatography (GC). The TPH removal in all treatments ranged between 2 and 67%, regardless of the addition of microbial consortiums, amendments, or surfactants within the tested parameters. The results of this study demonstrated that bioremediation of heavy oily sludge presents greater challenges to achieve regulatory requirements. Additional physicochemical treatments analysis to remediate this recalcitrant material may be required to achieve a desirable degradation rate.

Phytoremediation of soil contaminated with weathered petroleum hydrocarbons by applying mineral fertilization, an anionic surfactant, or hydrocarbonoclastic bacteria.

This study evaluated the effect of the application of mineral fertilization (F), the anionic surfactant Triton X-100 (TX100), or the inoculation with a hydrocarbooclastic bacterial consortium (BCons) on the growth of Clitoria ternatea during the phytoremediation of a Gleysol contaminated with weathered petroleum hydrocarbons (39,000 mg kg-1 WPH) collected from La Venta, Tabasco (Mexico). The experiment consisted of a completely randomized design with seven treatments and four replications each under greenhouse conditions. The application of F (biostimulation) increased plant growth and biomass production; in contrast, TX100 only favored root biomass (11%) but significantly favored WPH degradation. Bioaugmentation with BCons did not show significant effects on plant growth. Nevertheless, the combination of biostimulation with bioaugmentation (BCons + F, BCons + TX100, and BCons + F+TX100) enhanced plant growth, hydrocarbonoclastic bacteria population, and WPH degradation when compared to treatments with the single application of bioaugmentation (BCons) or biostimulation (F).

Application of mineral fertilization and commercial surfactant favored root biomass and degradation of weathered petroleum hydrocarbons (WPH). The reintroduction of hydrocarbonoclastic and surfactant-producer bacteria did not enhance plant growth but significantly contributed on WPH degradation from a chronically contaminated soil.

Burkholderia vietnamiensis G4 as a biological agent in bioremediation processes of polycyclic aromatic hydrocarbons in sludge farms.

Polycyclic aromatic hydrocarbons (PAHs) are one of the main pollutants generated by the refining and use of oil. To search bioremediation alternatives for these compounds, mainly in situ, considering the biotic and abiotic variables that affect the contaminated sites is determinant for the success of bioremediation techniques. In this study, bioremediation strategies were evaluated in situ, including biostimulation and bioaugmentation for 16 priority PAHs present in activated sludge farms. B. vietnamiensis G4 was used as a biodegradation agent for bioaugmentation tests. The analyses occurred for 12 months, and temperature and humidity were measured to verify the effects of these factors on the biodegradation. We used the technique GC-MS to evaluate and quantify the degradation of PAHs over the time of the experiment. Of the four treatments applied, bioaugmentation with quarterly application proved to be the best strategy, showing the degradation of compounds of high (34.4% annual average) and low (21.9% annual average) molecular weight. A high degradation rate for high molecular weight compounds demonstrates that this technique can be successfully applied in bioremediation of areas with compounds considered toxic and stable in nature, contributing to the mitigation of impacts generated by PAHs.

Actinobacteria bioaugmentation and substrate evaluation for biobeds useful for the treatment of atrazine residues in agricultural fields.

Biopurification systems (BPS) or biobeds are bioprophylaxis systems to prevent pesticide point-source contamination, whose efficiency relies mostly on the pesticide removal capacity of the biomixture, the majority component of a BPS. The adaptation of the components of the biomixtures to local availabilities is a key aspect to ensure the sustainability of the system. In this work, the removal of atrazine (ATZ) was evaluated in biomixtures formulated with three sugarcane by-products as alternative lignocellulosic substrates. Based on the capacity of actinobacteria to tolerate and degrade diverse pesticides, the effect of biomixtures bioaugmentation with actinobacteria was evaluated as a strategy to enhance the depuration capacity of biobeds. Also, the effect of ATZ and/or the bioaugmentation on microbial developments and enzymatic activities were studied. The biomixtures formulated with bagasse, filter cake, or harvest residue, reached pesticide removal values of 37-41% at 28 d of incubation, with t1/2 between 37.9 ± 0.4 d and 52.3 ± 0.4 d. The bioaugmentation with Streptomyces sp. M7 accelerated the dissipation of the pesticide in the biomixtures, reducing ATZ t1/2 3-fold regarding the controls, and achieving up to 72% of ATZ removal. Atrazine did not exert a clear effect on microbial developments, although most of the microbial counts were less in the contaminated biomixtures at the end of the assay. The bioaugmentation improved the development of the microbiota in general, specially actinobacteria and fungi, regarding the non-bioaugmented systems. The inoculation with Streptomyces sp. M7 enhanced acid phosphatase activity and/or reversed a possible effect of the pesticide over this enzymatic activity.

Enhanced biodegradation of hexachlorocyclohexane (HCH) isomers by Sphingobium sp. strain D4 in the presence of root exudates or in co-culture with HCH-mobilizing strains.

Lindane and other 1,2,3,4,5,6-hexachlorocyclohexane (HCH) isomers are persistent organic pollutants highly hydrophobic, which hampers their availability and biodegradation. This work aimed at (i) investigating genes encoding enzymes involved in HCH degradation in the bacterium Sphingobium sp. D4, (ii) selecting strains, from a collection of environmental isolates, able to mobilize HCHs from contaminated soil, and (iii) analysing the biodegradation of HCHs by strain D4 in co-culture with HCH-mobilizing strains or when cultivated with root exudates. Fragments of the same size and similar sequence to linA and linB genes were successfully amplified. Two isolates, Streptomyces sp. M7 and Rhodococcus erythropolis ET54b able to produce emulsifiers and to mobilize HCH isomers from soil were selected. Biodegradation of HCH isomers by strain D4 was enhanced when co-inoculated with HCH mobilizing strains or when cultivated with root exudates. The degrader strain D4 was able to decompose very efficiently HCHs isomers, reducing their concentration in soil slurries by more than 95% (from an average initial amount of 50 ± 8 mg HCH kg-1 soil) in 9 days. The combination of HCH-degrading and HCH-mobilizing strains can be considered a promising inoculum for future soil bioremediation studies using bioaugmentation techniques or in combination with plants in rhizodegradation assays.

Synergy of the Tropical Earthworm Pontoscolex corethrurus and Oil Palm Bagasse in the Removal of Heavy Crude Oil.

The tropical endogeic earthworm Pontoscolex corethrurus, a non-standard species used in ecotoxicity, has been found in crude oil-contaminated habitats. We estimated the removal of total hydrocarbons from heavy crude "Maya" oil on an artificially contaminated soil with a median lethal concentration of P. corethrurus and an addition of oil palm bagasse. P. corethrurus had a high survival rate, and the addition of oil palm bagasse led to a greater growth and an increase in abundance of bacteria and fungi. The activity of P. corethrurus and the nutritional quality of oil palm bagasse had a significant impact on the removal of a larger amount of petroleum hydrocarbons from contaminated soil. We concluded that the endogeic earthworm P. corethrurus and oil palm bagasse acted synergistically to achieve a more effective removal of total petroleum hydrocarbons from soil. These results show the potential for using P. corethrurus to remove, either directly or indirectly, crude oil from soil.

Evaluation of in situ biosurfactant production by inoculum of P. putida and nutrient addition for the removal of polycyclic aromatic hydrocarbons from aged oil-polluted soil.

This work aimed to conduct a laboratory study to evaluate the use of Pseudomonas putida CB-100 and nutrient addition for the removal of PAHs from an aged oil-polluted soil of Veracruz, Mexico. Pseudomonas putida is a biosurfactant-producing bacterium capable of metabolizing polycyclic aromatic hydrocarbons (PAHs), which are toxic compounds with low water solubility, high melting, and boiling points, and low vapor pressure; characteristics that increase as their molecular weight increases and make them more recalcitrant. The methodology consisted in sampling the long-term oil-polluted soil and testing the use of Gamma irradiation (25 kGy) for the sterilization of the soil for abiotic control. We evaluated serological bottles containing 20 g of 35% moist soil (irradiated and non-irradiated) with the following treatments: the addition of nutrients (NH4Cl, NaNO3, KH2PO4, and K2HPO4), an inoculum of P. putida, and both P. putida and nutrients. The parameters assessed were pH, organic matter, humidity, available phosphorus, total nitrogen, cultivable heterotrophic microorganisms, CO2 production, rhamnolipids, surface tension, and the removal of eleven PAHs. The non-irradiated soil added with P. putida was the most efficient in the removal of PAHs; the pattern was: Benzo(a)anthracene > Phenanthrene > Fluoranthene > Benzo(k)fluoranthene > Chrysene > Pyrene > Anthracene > Acenaphthylene > Benzo(b)fluoranthene. In conclusion, P. putida in the non-irradiated soil produced in situ biosurfactants (1.55 mg/kg of rhamnolipids and an 11.9 mN/m decrease in surface tension) and removed PAHs in 10 days.

Bioaugmentation of pilot-scale slow sand filters can achieve compliant levels for the micropollutant metaldehyde in a real water matrix.

Metaldehyde is a polar, mobile, low molecular weight pesticide that is challenging to remove from drinking water with current adsorption-based micropollutant treatment technologies. Alternative strategies to remove this and compounds with similar properties are necessary to ensure an adequate supply of safe and regulation-compliant drinking water. Biological removal of metaldehyde below the 0.1 µg•L-1 regulatory concentration was attained in pilot-scale slow sand filters (SSFs) subject to bioaugmentation with metaldehyde-degrading bacteria. To achieve this, a library of degraders was first screened in bench-scale assays for removal at micropollutant concentrations in progressively more challenging conditions, including a mixed microbial community with multiple carbon sources. The best performing strains, A. calcoaceticus E1 and Sphingobium CMET-H, showed removal rates of 0.0012 µg•h-1•107 cells-1 and 0.019 µg•h-1•107 cells-1 at this scale. These candidates were then used as inocula for bioaugmentation of pilot-scale SSFs. Here, removal of metaldehyde by A. calcoaceticus E1, was insufficient to achieve compliant water regardless testing increasing cell concentrations. Quantification of metaldehyde-degrading genes indicated that aggregation and inadequate distribution of the inoculum in the filters were the likely causes of this outcome. Conversely, bioaugmentation with Sphingobium CMET-H enabled sufficient metaldehyde removal to achieve compliance, with undetectable levels in treated water for at least 14 d (volumetric removal: 0.57 µg•L-1•h-1). Bioaugmentation did not affect the background SSF microbial community, and filter function was maintained throughout the trial. Here it has been shown for the first time that bioaugmentation is an efficient strategy to remove the adsorption-resistant pesticide metaldehyde from a real water matrix in upscaled systems. Swift contaminant removal after inoculum addition and persistent activity are two remarkable attributes of this approach that would allow it to effectively manage peaks in metaldehyde concentrations (due to precipitation or increased application) in incoming raw water by matching them with high enough degrading populations. This study provides an example of how stepwise screening of a diverse collection of degraders can lead to successful bioaugmentation and can be used as a template for other problematic adsorption-resistant compounds in drinking water purification.

Biodegradação do herbicida atrazina por Saccharomyces cerevisiae / Biodegradation of the atrazine herbicide by Saccharomyces cerevisiae

RESUMO Tendo em vista os vários problemas ambientais e de saúde que o uso crescente de agrotóxicos vem causando, é necessário a otimização de técnicas que visem a sua rápida degradação. A atrazina é um herbicida utilizado no controle de ervas daninhas, principalmente nas culturas de milho e cana-de-açúcar. Nesse sentido, o objetivo deste estudo foi verificar a eficiência da levedura Saccharomyces cerevisiae na degradação do herbicida atrazina em solo contaminado com diferentes concentrações do produto comercial. Foi igualmente testado o efeito da adição de palha de milho no experimento. A fim de determinar a quantidade de gás carbônico (CO2) liberado durante os ensaios, o qual reflete a atividade da microbiota do solo responsável pela degradação de compostos orgânicos, foi utilizada a técnica da respiração basal do solo. E, paralelamente a isso, para verificar a concentração de atrazina ao longo do experimento (tempo inicial, aos 7, 14 e 63 dias), foi utilizada a análise de cromatografia gasosa acoplada ao espectrômetro de massas (CG-MS). Por meio da análise estatística dos dados de respiração basal do solo, o fator de bioaumento com a levedura foi o mais significativo, seguido da adição de palha de milho. Verificou-se o declínio da concentração de atrazina por intermédio das análises cromatográficas. Assim, sugere-se que a biorremediação com S. cerevisiae tem potencial para elevar as taxas de degradação do herbicida no solo.

ABSTRACT Considering the various environmental and health problems that the increasing use of pesticides has been causing, it is necessary to optimize techniques aimed at their rapid degradation. Atrazine is a herbicide used to control weeds, especially in maize and sugarcane crops. Thus, the objective of this study was to verify the efficiency of the Saccharomyces cerevisiae yeast in the degradation of the herbicide atrazine in soil contaminated with different concentrations of the commercial product. The effect of addition of corn straw on the experiment was also tested. In order to determine the amount of carbon dioxide (CO2) released during the tests, which reflects the activity of the soil microorganism responsible for the degradation of organic compounds, the soil basal respiration technique was used. At the same time, the concentration of atrazine during the experiment (start time, at 7, 14, and 63 days) was analyzed by gas chromatography coupled to the mass spectrometer (CG-MS). Through the statistical analysis of the basal respiration data of the soil, the bioaugmentation factor with yeast was the most significant, followed by the addition of corn straw, and the decline in atrazine concentration was verified through chromatographic analyses. Thus, it is suggested that bioremediation with S. cerevisiae has the potential to increase the rates of degradation of the herbicide in the soil.

Bioaugmentation of Native Fungi, an Efficient Strategy for the Bioremediation of an Aged Industrially Polluted Soil With Heavy Hydrocarbons.

The concurrence of structurally complex petroleum-associated contaminants at relatively high concentrations, with diverse climatic conditions and textural soil characteristics, hinders conventional bioremediation processes. Recalcitrant compounds such as high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) and heavy alkanes commonly remain after standard soil bioremediation at concentrations above regulatory limits. The present study assessed the potential of native fungal bioaugmentation as a strategy to promote the bioremediation of an aged industrially polluted soil enriched with heavy hydrocarbon fractions. Microcosms assays were performed by means of biostimulation and bioaugmentation, by inoculating a defined consortium of six potentially hydrocarbonoclastic fungi belonging to the genera Penicillium, Ulocladium, Aspergillus, and Fusarium, which were isolated previously from the polluted soil. The biodegradation performance of fungal bioaugmentation was compared with soil biostimulation (water and nutrient addition) and with untreated soil as a control. Fungal bioaugmentation resulted in a higher biodegradation of total petroleum hydrocarbons (TPH) and of HMW-PAHs than with biostimulation. TPH (C14-C35) decreased by a 39.90 ± 1.99% in bioaugmented microcosms vs. a 24.17 ± 1.31% in biostimulated microcosms. As for the effect of fungal bioaugmentation on HMW-PAHs, the 5-ringed benzo(a)fluoranthene and benzo(a)pyrene were reduced by a 36% and 46%, respectively, while the 6-ringed benzoperylene decreased by a 28%, after 120 days of treatment. Biostimulated microcosm exhibited a significantly lower reduction of 5- and 6-ringed PAHs (8% and 5% respectively). Higher TPH and HMW-PAHs biodegradation levels in bioaugmented microcosms were also associated to a significant decrease in acute ecotoxicity (EC50) by Vibrio fischeri bioluminiscence inhibition assays. Molecular profiling and counting of viable hydrocarbon-degrading bacteria from soil microcosms revealed that fungal bioaugmentation promoted the growth of autochthonous active hydrocarbon-degrading bacteria. The implementation of such an approach to enhance hydrocarbon biodegradation should be considered as a novel bioremediation strategy for the treatment of the most recalcitrant and highly genotoxic hydrocarbons in aged industrially polluted soils.

New Role for a Commercially Available Bioinsecticide: Bacillus thuringiensis Berliner Biodegrades the Pyrethroid Cypermethrin.

The microbial diversity of several environments has been explored by researchers for the biodegradation of pyrethroids. In this study, a new approach was employed aiming at the use of Bacillus thuringiensis Berliner, a strain commercially available as bioinsecticide, for Cypermethrin (Cyp) biodegradation. This bacterial strain grew in the presence of Cyp and biodegraded this xenobiotic in a liquid medium. A central composite design for surface response methodology was employed for biodegradation. Under optimized conditions (50 mg·L-1 of Cyp, pH 8.5, 37 °C), 83.5% biodegradation was determined with the production of 12.0 ± 0.6 mg·L-1 3-phenoxybenzoic acid after 5 days. Moreover, a biodegradation pathway with the 18 compounds identified by GC-MS and LC-MS/MS was proposed. Experiments in soil for 28 days at 30 °C were performed, and 16.7% Cyp degradation was determined under abiotic conditions, whereas 36.6 ± 1.9% biodegradation was observed for B. thuringiensis Berliner with the native microbiome, indicating that bioaugmentation with this strain promoted a significant increase in the Cyp decontamination. Therefore, B. thuringiensis Berliner can act as biodegrader agent and insecticide at the same time, promoting decontamination of chemicals as Cyp while maintaining the protection of crops against insects. Moreover, B. thuringiensis species can produce bacteriocins with antifungal activity, which may increase agricultural productivity.