Effect of the metals iron, copper and silver on fluorobenzene biodegradation by Labrys portucalensis

Fungal biomineralization of toxic metals accelerates organic pollutant removal

Fungal biomineralization plays an important role in the biogeochemical cycling of metals in the environment and has been extensively explored for bioremediation and element biorecovery. However, the cellular and metabolic responses of fungi in the presence of toxic metals during biomineralization and their impact on organic matter transformations are unclear. This is an important question because co-contamination by toxic metals and organic pollutants is a common phenomenon in the natural environment. In this research, the biomineralization process and oxidative stress response of the geoactive soil fungus Aspergillus niger were investigated in the presence of toxic metals (Co, Cu, Mn, and Fe) and the azo dye orange II (AO II). We have found that the co-existence of toxic metals and AO II not only enhanced the fungal biomineralization of toxic metals but also accelerated the removal of AO II. We hypothesize that the fungus and in situ mycogenic biominerals (toxic metal oxalates) constituted a quasi-bioreactor, where the biominerals removed organic pollutants by catalyzing reactive oxygen species (ROS) generation resulting from oxidative stress. We have therefore demonstrated that a fungal/biomineral system can successfully achieve the goal of toxic metal immobilization and organic pollutant decomposition. Such findings inform the potential development of fungal-biomineral hybrid systems for mixed pollutant bioremediation as well as provide further understanding of fungal organic-inorganic pollutant transformations in the environment and their importance in biogeochemical cycles.

Microbiological status of natural and anthropogenic soils of the Taganrog Bay coast at different levels of combined pollution with heavy metals and PAHs

The effect of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) pollution on the microbiological status of soils on the coast of the Taganrog Bay and adjacent areas was studied. The content of total and exchangeable forms of HMs, the content of 16 priority PAHs and the abundance of several groups of culturable microorganisms was determined, namely copiotrophic, prototrophic, aerobic spore-forming bacteria, actinomycetes, molds and yeasts. The content of total and exchangeable forms of HMs in urban coastal soils in industrial zone significantly exceeded that in non-urban soils. The maximum concentrations of total forms of Mn, Cr, Ni, Cu, Zn, Pb and Cd are 1821, 871, 143, 89, 1390, 317 and 10 mg/kg, respectively. The median value of the total content of 16 PAHs in urban soils is 3 times higher than in the soils of natural areas and reached 4309 ng/g. The lowest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were found in the soils of industrial zone: 6.8, 13.8 and 0.63 million CFU g-1 dry soil, respectively. The largest numbers of copiotrophic bacteria, prototrophic bacteria and aerobic spore-forming bacteria were recorded in the soils of natural areas-72.5, 136 and 5.73 million CFU g-1 dry soil, respectively. It was found that the abundance of copiotrophs, prototrophs, and aerobic spore-forming bacteria is more affected by the urbanization of coastal soils including the pollution of HMs and PAHs. Other groups of microorganisms (actinomycetes, molds and yeasts) turned out to be more resistant to anthropogenic factors.

Biodegradation and Metabolic Pathway of the Neonicotinoid Insecticide Thiamethoxam by Labrys portucalensis F11

Thiamethoxam (TMX) is an effective neonicotinoid insecticide. However, its widespread use is detrimental to non-targeted organisms and water systems. This study investigates the biodegradation of this insecticide by Labrys portucalensis F11. After 30 days of incubation in mineral salt medium, L. portucalensis F11 was able to remove 41%, 35% and 100% of a supplied amount of TMX (10.8 mg L^-1) provided as the sole carbon and nitrogen source, the sole carbon and sulfur source and as the sole carbon source, respectively. Periodic feeding with sodium acetate as the supplementary carbon source resulted in faster degradation of TMX (10.8 mg L^-1); more than 90% was removed in 3 days. The detection and identification of biodegradation intermediates was performed by UPLC-QTOF/MS/MS. The chemical structure of 12 metabolites is proposed. Nitro reduction, oxadiazine ring cleavage and dechlorination are the main degradation pathways proposed. After biodegradation, toxicity was removed as indicated using Aliivibrio fischeri and by assessing the synthesis of an inducible β-galactosidase by an E. coli mutant (Toxi-Chromo test). L. portucalensis F11 was able to degrade TMX under different conditions and could be effective in bioremediation strategies.

Biological removal processes in aerobic granular sludge exposed to diclofenac

Diclofenac is a worldwide consumed drug included in the watch list of substances to be monitored according to the European Union Water Framework Directive (Directive 2013/39/EU). Aerobic granular sludge sequencing batch reactors (AGS-SBR) are increasingly used for wastewater treatment but there is scant information on the fate and effect of micropollutants to nutrient removal processes. An AGS-SBR fed with synthetic wastewater containing diclofenac was bioaugmented with a diclofenac degrading bacterial strain and performance and microbial community dynamics was analysed. Chemical oxygen demand, phosphate and ammonia removal were not affected by the micropollutant at 0.03 mM (9.54 mg L^-1). The AGS was able to retain the degrading strain, which was detected in the sludge throughout after augmentation. Nevertheless, besides some adsorption to the biomass, diclofenac was not degraded by the augmented sludge given the short operating cycles and even if batch degradation assays confirmed that the bioaugmented AGS was able to biodegrade the compound. The exposure to the pharmaceutical affected the microbial community of the sludge, separating the two first phases of reactor operation (acclimatization and granulation) from subsequent phases. The AGS was able to keep the bioaugmented strain and to maintain the main functions of nutrient removal even through the long exposure to the pharmaceutical, but combined strategies are needed to reduce the spread of micropollutants in the environment.

Biodegradation and Metabolic Pathway of 17β-Estradiol by Rhodococcus sp. ED55

Endocrine disrupting compounds (EDCs) in the environment are considered a motif of concern, due to the widespread occurrence and potential adverse ecological and human health effects. The natural estrogen, 17β-estradiol (E2), is frequently detected in receiving water bodies after not being efficiently removed in conventional wastewater treatment plants (WWTPs), promoting a negative impact for both the aquatic ecosystem and human health. In this study, the biodegradation of E2 by Rhodococcus sp. ED55, a bacterial strain isolated from sediments of a discharge point of WWTP in Coloane, Macau, was investigated. Rhodococcus sp. ED55 was able to completely degrade 5 mg/L of E2 in 4 h in a synthetic medium. A similar degradation pattern was observed when the bacterial strain was used in wastewater collected from a WWTP, where a significant improvement in the degradation of the compound occurred. The detection and identification of 17 metabolites was achieved by means of UPLC/ESI/HRMS, which proposed a degradation pathway of E2. The acute test with luminescent marine bacterium Aliivibrio fischeri revealed the elimination of the toxicity of the treated effluent and the standardized yeast estrogenic (S-YES) assay with the recombinant strain of Saccharomyces cerevisiae revealed a decrease in the estrogenic activity of wastewater samples after biodegradation.

Optimization of media composition for enhancing tetracycline degradation by Trichosporon mycotoxinivorans XPY-10 using response surface methodology

The objective of the study was to improve tetracycline degradation efficiency by Trichosporon mycotoxinivorans XPY-10 using statistical experimental designs. Different culture conditions (FeSO₄, pH and glucose) were optimized for tetracycline biodegradation and the mutual interactions between these three variables were analysed using Box-Behnken design (BBD) and response surface methodology (RSM). The results showed that the empirical model was suitable for experimental data, and the maximum tetracycline degradation efficiency by XPY-10 was 95.18% under the optimum conditions of 0.02% of FeSO₄, pH 7.83 and 0.28% of glucose, which was further verified by experiments. This study indicated the excellent ability of XPY-10 in degrading tetracycline and theoretical support for the follow-up practice to remediate tetracycline contaminated environment.

Sediments in the mangrove areas contribute to the removal of endocrine disrupting chemicals in coastal sediments of Macau SAR, China, and harbour microbial communities capable of degrading E2, EE2, BPA and BPS

The occurrence of endocrine disrupting chemicals (EDCs) is a major issue for marine and coastal environments in the proximity of urban areas. The occurrence of EDCs in the Pearl River Delta region is well documented but specific data related to Macao is unavailable. The levels of bisphenol-A (BPA), estrone (E1), 17α-estradiol (αE2), 17β-estradiol (E2), estriol (E3), and 17α-ethynylestradiol (EE2) were measured in sediment samples collected along the coastline of Macao. BPA was found in all 45 collected samples with lower BPA concentrations associated to the presence of mangrove trees. Biodegradation assays were performed to evaluate the capacity of the microbial communities of the surveyed ecosystems to degrade BPA and its analogue BPS. Using sediments collected at a WWTP discharge point as inoculum, at a concentration of 2 mg l^-1 complete removal of BPA was observed within 6 days, whereas for the same concentration BPS removal was of 95% after 10 days, which is particularly interesting since this compound is considered recalcitrant to biodegradation and likely to accumulate in the environment. Supplementation with BPA improved the degradation of bisphenol-S (BPS). Aiming at the isolation of EDCs-degrading bacteria, enrichments were established with sediments supplied with BPA, BPS, E2 and EE2, which led to the isolation of a bacterial strain, identified as Rhodoccoccus sp. ED55, able to degrade the four compounds at different extents. The isolated strain represents a valuable candidate for bioremediation of contaminated soils and waters.

Mechanistic insight to mycoremediation potential of a metal resistant fungal strain for removal of hazardous metals from multimetal pesticide matrix

Fungi have an exceptional capability to flourish in presence of heavy metals and pesticide. However, the mechanism of bioremediation of pesticide (lindane) and multimetal [mixture of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn)] by a fungus is little understood. In the present study, Aspergillus fumigatus, a filamentous fungus was found to accumulate heavy metals in the order [Zn(98%)>Pb(95%)>Cd(63%)>Cr(62%)>Ni(46%)>Cu(37%)] from a cocktail of 30 mg L^-1 multimetal and lindane (30 mg L^-1) in a composite media amended with 1% glucose. Particularly, Pb and Zn uptake was enhanced in presence of lindane. Remarkably, lindane was degraded to 1.92 ± 0.01 mg L^-1 in 72 h which is below the permissible limit value (2.0 mg L^-1) for the discharge of lindane into the aquatic bodies as prescribed by European Community legislation. The utilization of lindane as a cometabolite from the complex environment was evident by the phenomenal growth of the fungal pellet biomass (5.89 ± 0.03 g L^-1) at 72 h with cube root growth constant of fungus (0.0211 g^1/3 L^-1/3 h^-1) compared to the biomasses obtained in case of the biotic control as well as in presence of multimetal complex without lindane. The different analytical techniques revealed the various stress coping strategies adopted by A. fumigatus for multimetal uptake in the simultaneous presence of multimetal and pesticide. From the Transmission electron microscope coupled energy dispersive X-ray analysis (TEM-EDAX) results, uptake of the metals Cd, Cu and Pb in the cytoplasmic membrane and the accumulation of the metals Cr, Ni and Zn in the cytoplasm of the fungus were deduced. Fourier-transform infrared spectroscopy (FTIR) revealed involvement of carboxyl/amide group of fungal cell wall in metal chelation. Thus A. fumigatus exhibited biosorption and bioaccumulation as the mechanisms involved in detoxification of multimetals.

Carbamazepine is degraded by the bacterial strain Labrys portucalensis F11

The occurrence of pharmaceuticals in the environment is a topic of concern. Carbamazepine (CBZ) is a widespread antiepileptic drug and due to its physical-chemical characteristics minimal removal is achieved in conventional water treatments, and thus has been suggested as a molecular marker of wastewater contamination in surface water and groundwater. The present study reports the biotransformation of CBZ by the bacterial strain Labrys portucalensis F11. When supplied as a sole carbon source, a 95.4% biotransformation of 42.69 μM CBZ was achieved in 30 days. In co-metabolism with acetate, complete biotransformation was attained at a faster rate. Following a target approach, the detection and identification of 14 intermediary metabolites was achieved through UPLC-QTOF/MS/MS. Biotransformation of CBZ by the bacterial strain is mostly based on oxidation, loss of -CHNO group and ketone formation reactions; a biotransformation pathway with two routes is proposed. The toxicity of untreated and treated CBZ solutions was assessed using Vibrio Fischeri and Lepidium sativum acute toxicity tests and Toxi-Chromo Test. The presence of CBZ and/or its degradations products in solution resulted in moderate toxic effect on Vibrio Fischeri, whereas the other organisms were not affected. To the best of our knowledge this is the first report that proposes the metabolic degradation pathway of CBZ by a single bacterial strain.

Biodegradation of Diclofenac by the bacterial strain Labrys portucalensis F11

Diclofenac (DCF) is a widely used non-steroidal anti-inflammatory pharmaceutical which is detected in the environment at concentrations which can pose a threat to living organisms. In this study, biodegradation of DCF was assessed using the bacterial strain Labrys portucalensis F11. Biotransformation of 70% of DCF (1.7-34 μM), supplied as the sole carbon source, was achieved in 30 days. Complete degradation was reached via co-metabolism with acetate, over a period of 6 days for 1.7 µM and 25 days for 34 μM of DCF. The detection and identification of biodegradation intermediates was performed by UPLC-QTOF/MS/MS. The chemical structure of 12 metabolites is proposed. DCF degradation by strain F11 proceeds mainly by hydroxylation reactions; the formation of benzoquinone imine species seems to be a central step in the degradation pathway. Moreover, this is the first report that identified conjugated metabolites, resulting from sulfation reactions of DCF by bacteria. Stoichiometric liberation of chlorine and no detection of metabolites at the end of the experiments are strong indications of complete degradation of DCF by strain F11. To the best of our knowledge this is the first report that points to complete degradation of DCF by a single bacterial strain isolated from the environment.

Geographic distribution of cadmium and its interaction with the microbial community in the Longjiang River: risk evaluation after a shocking pollution accident

A shocking Longjiang River cadmium pollution accident occurred in 2012, the effects of which on microbial communities remain unclear. Alkaline precipitation technology was applied for remediation, but concerns rose about the stability of this technology. To understand the geographic distribution of cadmium and its correlation with microbes, in this study, 39 water samples and 39 sludge samples from this river and 2 soil samples from the nearby farmland were collected for chemical and microbial analyses. The Cd concentrations of all water samples were lower than 0.005 mg/L and reached the quality standards for Chinese surface water. A ranking of sludge samples based on Cd contents showed sewage outfall > dosing sites > farmland, all of which were higher than the quality standard for soil. Alkaline precipitation technology was effective for Cd precipitation. Cd was unstable; it was constantly dissolving and being released from the sludge. The Cd content of each phase was mainly influenced by the total Cd content. Over 40,000 effective sequences were detected in each sample, and a total of 59,833 OTUs and 1,273 genera were found using Illumina MiSeq sequencing. Two phyla and 39 genera were notably positively correlated with the Cd distribution, while the cases of 10 phyla and 6 genera were the opposite.

Simultaneous Cr(VI) removal and 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) biodegradation by Pseudomonas aeruginosa in liquid medium

Simultaneous Cr(VI) removal and 2,2',4,4'-tetra brominated diphenyl ether (BDE-47) biodegradation by Pseudomonas aeruginosa in liquid medium were investigated in this study, with the goal of elucidating the interaction between concomitant pollutants Cr(VI) and BDE-47 during microbial remediation. The experimental results revealed that the degradation efficiency of 1 mg L(-1) BDE-47 by 60 mg L(-1) biomass achieved 51.3% within 7 d when 2 mg L(-1) Cr(VI) coexisted. The degradation efficiency was accelerated at low concentrations of Cr(VI) (≤5 mg L(-1)), but inhibited at higher levels (≥10 mg L(-1)). Cr(VI) of 2 mg L(-1) facilitated the secretion of rhamnolipid from the strain, altered cell surface hydrophobicity and cell membrane permeability, and promoted intracellular BDE-47 accumulation, thus improving BDE-47 biotransformation. In addition, the stimulation of intracellular enzyme synthesis by 2 mg L(-1) Cr(VI) contributed to more BDE-47 elimination in the cells. The achievement of BDE-47 biodegradation was coupled with cell growth, enzyme extraction, cell membrane permeability change, and ATPase activity increase. The study also indicated that the improvement of Cr(VI) removal in BDE-47/Cr(VI) co-contaminated condition was mostly due to the increasing synthesis of extracellular enzyme in the presence of low concentrations of BDE-47. The whole study demonstrated that P. aeruginosa was available for the removal of toxic Cr(VI) and degradation of BDE-47 simultaneously in the liquid.

Versatility of Streptomyces sp. M7 to bioremediate soils co-contaminated with Cr(VI) and lindane

The aim of this work was to study the impact of environmental factors on the bioremediation of Cr(VI) and lindane contaminated soil, by an actinobacterium, Streptomyces sp. M7, in order to optimize the process. Soil samples were contaminated with 25 µg kg(-1) of lindane and 50 mg kg(-1) of Cr(VI) and inoculated with Streptomyces sp. M7. The lowest inoculum concentration which simultaneously produced highest removal of Cr(VI) and lindane was 1 g kg(-1). The influence of physical and chemical parameters was assessed using a full factorial design. The factors and levels tested were: Temperature: 25, 30, 35°C; Humidity: 10%, 20%, 30%; Initial Cr(VI) concentration: 20, 50, 80 mg kg(-1); Initial lindane concentration: 10, 25, 40 µg kg(-1). Streptomyces sp. M7 exhibited strong versatility, showing the ability to bioremediate co-contaminated soil samples at several physicochemical conditions. Streptomyces sp. M7 inoculum size was optimized. Also, it was fitted a model to study this process, and it was possible to predict the system performance, knowing the initial conditions. Moreover, optimum temperature and humidity conditions for the bioremediation of soil with different concentrations of Cr(VI) and lindane were determined. Lettuce seedlings were a suitable biomarker to evaluate the contaminants mixture toxicity. Streptomyces sp. M7 carried out a successful bioremediation, which was demonstrated through ecotoxicity test with Lactuca sativa.

Degradation of toluene by ortho cleavage enzymes in Burkholderia fungorum FLU100

Burkholderia fungorum FLU100 simultaneously oxidized any mixture of toluene, benzene and mono-halogen benzenes to (3-substituted) catechols with a selectivity of nearly 100%. Further metabolism occurred via enzymes of ortho cleavage pathways with complete mineralization. During the transformation of 3-methylcatechol, 4-carboxymethyl-2-methylbut-2-en-4-olide (2-methyl-2-enelactone, 2-ML) accumulated transiently, being further mineralized only after a lag phase of 2 h in case of cells pre-grown on benzene or mono-halogen benzenes. No lag phase, however, occurred after growth on toluene. Cultures inhibited by chloramphenicol after growth on benzene or mono-halogen benzenes were unable to metabolize 2-ML supplied externally, even after prolonged incubation. A control culture grown with toluene did not show any lag phase and used 2-ML as a substrate. This means that 2-ML is an intermediate of toluene degradation and converted by specific enzymes. The conversion of 4-methylcatechol as a very minor by-product of toluene degradation in strain FLU100 resulted in the accumulation of 4-carboxymethyl-4-methylbut-2-en-4-olide (4-methyl-2-enelactone, 4-ML) as a dead-end product, excluding its nature as a possible intermediate. Thus, 3-methylcyclohexa-3,5-diene-1,2-diol, 3-methylcatechol, 2-methyl muconate and 2-ML were identified as central intermediates of productive ortho cleavage pathways for toluene metabolism in B. fungorum FLU100.