Alachlor oxidation by the filamentous fungus Paecilomyces marquandii

Occurrence, ecological risk, and advanced removal methods of herbicides in waters: a timely review

Coastal pollution caused by the importation of agricultural herbicides is one of the main environmental problems that directly affect the coastal primary productivity and even the safety of human seafood. It is urgent to evaluate the ecological risk objectively and explore feasible removal strategies. However, existing studies focus on the runoff distribution and risk assessment of specific herbicides in specific areas, and compared with soil environment, there are few studies on remediation methods for water environment. Therefore, we systematically reviewed the current situation of herbicide pollution in global coastal waters and the dose-response relationships of various herbicides on phytoplankton and higher trophic organisms from the perspective of ecological risks. In addition, we believe that compared with the traditional single physical and chemical remediation methods, biological remediation and its combined technology are the most promising methods for herbicide pollution remediation currently. Therefore, we focus on the application prospects, challenges, and management strategies of new bioremediation systems related to biology, such as constructed wetlands, membrane bioreactor processes, and microbial co-metabolism, in order to provide more advanced methods for reducing herbicide pollution in the water environment.

Insights into the metabolic pathways and biodegradation mechanisms of chloroacetamide herbicides

Chloroacetamide herbicides are widely used around the world due to their high efficiency, resulting in increasing levels of their residues in the environment. Residual chloroacetamides and their metabolites have been frequently detected in soil, water and organisms and shown to have toxic effects on non-target organisms, posing a serious threat to the ecosystem. As such, rapid and efficient techniques that eliminate chloroacetamide residues from the ecosystem are urgently needed. Degradation of these herbicides in the environment mainly occurs through microbial metabolism. Microbial strains such as Acinetobacter baumannii DT, Bacillus altitudinis A16, Pseudomonas aeruginosa JD115, Sphingobium baderi DE-13, Catellibacterium caeni DCA-1, Stenotrophomonas acidaminiphila JS-1, Klebsiella variicola B2, and Paecilomyces marquandii can effectively degrade chloroacetamide herbicides. The degradation pathway of chloroacetamide herbicides in aerobic bacteria is mainly initiated by an N/C-dealkylation reaction, followed by aromatic ring hydroxylation and cleavage processes, whereas dechlorination is the initial reaction in anaerobic bacteria. The molecular mechanisms associated with bacterial degradation of chloroacetamide herbicides have been explored, with amidase, hydrolase, reductase, ferredoxin and cytochrome P450 oxygenase currently known to play a pivotal role in the catabolic pathways of chloroacetamides. The fungal pathway for the degradation of these herbicides is more complex with more diversified products, and the degradation enzymes and genes involved remain to be discovered. However, there are few reviews specifically summarizing the microbial degrading species and biochemical mechanisms of chloroacetamide herbicides. Here, we briefly summarize the latest progress resulting from research on microbial strain resources and enzymes involved in degradation of these herbicides and their corresponding genes. Furthermore, we explore the biochemical pathways and molecular mechanisms for biodegradation of chloroacetamide herbicides in depth, thereby providing a reference for further research on the bioremediation of such herbicides.

Biodegradation of Alachlor by a Newly Isolated Bacterium: Degradation Pathway and Product Analysis

Alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl]acetamide] is a chloroacetanilide herbicide and has been widely used as a selective pre-emergent and post-emergent herbicide to control weeds and grass. Due to its wide usage, direct application on the ground, high solubility in water, and moderate persistence, alachlor and its metabolites have been detected in various environments. Therefore, there is an increasing concern about the environmental fate of alachlor and its metabolites. Microbial biodegradation is a main method of removal of alachlor in the natural environment. In this study, we isolated new alachlor degrading bacterium and proposed a novel alachlor-degrading pathway. The alachlor-degrading bacterial strain, GC-A6, was identified as Acinetobacter sp. using 16S rRNA gene sequence analysis. Acinetobacter sp. GC-A6 utilized alachlor as its sole carbon source and degraded 100 mg L−1 of alachlor within 48 h, which was the highest alachlor degradation efficiency. The degradation pathway of alachlor was studied using GC-MS analysis. Alachlor was initially degraded to 2-chloro-N-(2,6-diethylphenyl) acetamide, which was further degraded to 2,6-diethylaniline and 7-ethylindoline, respectively. 2,6-Diethylaniline was transformed into N-(2,6-diethylphenyl) formamide. N-(2,6-diethylphenyl) formamide was a first-reported intermediate during the degrading pathway of alachlor by single isolate.

Bisphenol A Removal by the Fungus Myrothecium roridumIM 6482-Analysis of the Cellular and Subcellular Level

Bisphenol (BPA) is a key ingredient in the production of epoxy resins and some types of plastics, which can be released into the environment and alter the endocrine systems of wildlife and humans. In this study, the ability of the fungus M. roridumIM 6482 to BPA elimination was investigated. LC-MS/MS analysis showed almost complete removal of BPA from the growth medium within 72 h of culturing. Products of BPA biotransformation were identified, and their estrogenic activity was found to be lower than that of the parent compound. Extracellular laccase activity was identified as the main mechanism of BPA elimination. It was observed that BPA induced oxidative stress in fungal cells manifested as the enhancement in ROS production, membranes permeability and lipids peroxidation. These oxidative stress markers were reduced after BPA biodegradation (72 h of culturing). Intracellular proteome analyses performed using 2-D electrophoresis and MALDI-TOF/TOF technique allowed identifying 69 proteins in a sample obtained from the BPA containing culture. There were mainly structural and regulator proteins but also oxidoreductive and antioxidative agents, such as superoxide dismutase and catalase. The obtained results broaden the knowledge on BPA elimination by microscopic fungi and may contribute to the development of BPA biodegradation methods.

Atrazine biodegradation by mycoinsecticide Metarhizium robertsii: Insights into its amino acids and lipids profile

Atrazine, is one of major concern pesticides contaminating agricultural areas and ground water. Its microbial biodegradation seems to be the most efficient in terms of economic and environmental benefits. In the present work the cometabolic biodegradation of atrazine by the fungus Metarhizum robertsii IM 6519 during 10-day batch cultures was characterized. The herbicide was transformed to several hydroxy-, dechlorinated or dealkylated metabolites with the involvement of cytochrome P450 monooxygenases. The obtained metabolomics data revealed that atrazine induced oxidative stress (increased the levels of L-proline, L-ornithine, L-arginine, GABA and L-methionine), disruptions of the carbon and nitrogen metabolism (L-aspartic acid, L-asparagine, L-tyrosine, L-threonine, L-isoleucine, L-phenylalanine, 1-methyl-L-histidine, L-tryptophan, L-valine, L-alanine, O-phospho-L-serine, L-sarcosine or L-lysine) and caused an increase in the membrane fluidity (a rise in the phosphatidylcholines/phosphatidylethanolamines (PC/PE) ratio together with the growth of the taurine level). The increased level of hydroxyl derivatives of linoleic acid (9-HODE and 13-HODE) confirmed that atrazine induced lipid peroxidation. The presented results suggesting that M. robertsii IM 6519 might be applied in atrazine biodegradation and may bring up the understanding of the process of triazine biodegradation by Metarhizum strains.

Biotransformation and detoxification of chloroacetanilide herbicides by Trichoderma spp. with plant growth-promoting activities

Due to the increasing use of chlorinated organic compounds, environmental pollution is a key issue in agricultural and industrial areas. In this study, biodegradation of chloroacetanilide herbicides, such as alachlor and metolachlor, by eight fungal strains of Trichoderma spp. originating from different microorganism collections was investigated. The tested fungi converted 80-99% of alachlor and 40-79% of metolachlor after 7 days of incubation. Biotransformation of herbicides was performed mainly by dechlorination and hydroxylation reactions. Eight alachlor metabolites and four byproducts of metolachlor conversion were detected in Trichoderma cultures, including two metolachlor intermediates for the first time identified in fungi. Moreover, in the cultures of six Trichoderma strains supplemented with chloroacetanilides, a decrease in toxicity was observed toward tested Artemia franciscana crustaceans. Simultaneously, 7 days after the application of the spores of T. koningii IM 0956, T. citrinoviride IM 6325, T. harzianum KKP 534, T. viride KKP 792 and T. virens DSM 1963 the length of roots and shoots of rapeseed seedlings treated with alachlor or metolachlor significantly increased. All tested strains exhibited plant growth-promoting traits, such as siderophore production, 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity, and phosphate solubilization, even in the presence of chloroacetanilide herbicides.

Assessment of oxidative stress and phospholipids alterations in chloroacetanilides-degrading Trichoderma spp

To investigate the induction of oxidative stress and antioxidant response in the chloroacetanilides-degrading Trichoderma spp. under alachlor and metolachlor exposure, a comparative analysis using popular biomarkers was employed. An increased intracellular level of reactive oxygen species (ROS; especially superoxide anion [O₂^-]) as well as products of lipid and protein oxidation after 24 h incubation with the herbicides confirmed chloroacetanilide-induced oxidative stress in tested Trichoderma strains. However, the considerable decline in the ROS levels and the carbonyl group content (biomarkers of protein peroxidation) in a time-dependent manner and changes in the antioxidant enzyme activities indicated an active response against chloroacetanilide-induced oxidative stress and the mechanism of tolerance in tested fungi. Moreover, the tested herbicides clearly modified the phospholipids (PLs) content in Trichoderma spp. in the stationary phase of growth, which was manifested through the difference in phosphatidic acid (PA), phosphatidylethanolamine (PE) and phosphatidylcholines (PC) levels. Despite enhanced lipid peroxidation and changes in PLs in most tested fungi, only a slight modification in membrane integrity of Trichoderma spp. under chloroacetanilides exposure was noted. The obtained results suggest that the alterations in the antioxidant system and the PLs profile of Trichoderma spp. might be useful biomarkers of chloroacetanilide-induced oxidative stress.

Potential of Trichoderma koningii to eliminate alachlor in the presence of copper ions

The filamentous fungus Trichoderma koningii is capable of fast and effective eliminate alachlor (90% after 72 h when added separately and 80-60% in the presence of 1-5 mM of copper). After 168 h over 99% elimination of alachlor resulted in detoxification and was connected with the mitigation of reactive oxygen species (ROS) production. Using MS/MS techniques, seven dechlorinated and hydroxylated metabolites were identified. Cytochrome P450 and laccase participate in biotransformation of the herbicide by this non-ligninolytic fungus. Laccase activity is stimulated both by copper and the mixture of copper and alachlor, which seems to be important for combined pollutants. T. koningii is characterized by high tolerance to copper (up to 7.5 mM). The metal content in mycelia reached 0.9-7.76 mg in 1 g of dry biomass. Our results suggest that T. koningii strain seems to be a promising tool for bioremediation of agricultural areas co-contaminated with copper-based fungicides and chloroacetanilide herbicides.

Elimination and detoxification of 2,4-D by Umbelopsis isabellina with the involvement of cytochrome P450

The chemical 2,4-dichlorophenoxyacetic acid (2,4-D) is used in agriculture as a herbicide. Its intensive use has an adverse effect on the environment. This study involved examining the degradation of 2,4-D compound by the filamentous fungus Umbelopsis isabellina. After 5 days of incubation, 98% of the herbicide (added at 25 mg L^-1) was found to be removed. The elimination of 2,4-D by U. isabellina was connected with the formation of 2,4-dichlorophenol (2,4-DCP), which resulted in a 60% decrease in the sample toxicity toward Artemia franciscana larvae. The metabolism of 2,4-D was inhibited by the addition of metyrapone, a known cytochrome P450 inhibitor. It provides evidence that cytochrome P450 system is involved in 2,4-D metabolism in U. isabellina.

Biotransformation of Dimethenamid-P by the basidiomycete Irpex consors

Twenty-nine basidiomycetes were screened in surface and liquid cultures for their capability to biotransform the chloroacetamide herbicide Dimethenamid-P (DMTA-P). The basidiomycete Irpex consors converted 70% of the herbicide (0.5 g L^-1 DMTA-P) in liquid cultures within 6 days, applying a minimal medium under non-ligninolytic conditions. Nine transformation products of DMTA-P were identified by liquid chromatography-mass spectrometry analysis of the culture supernatants. The four main metabolites were isolated and subjected to GC-MS analysis and NMR spectroscopy. The analyses revealed that the thiophene ring was oxidized at three different positions. Metabolite M1 was identified as the S-oxide, which was isolable and relatively stable at room temperature. In metabolite M2, one methyl substituent of the thiophene ring was hydroxylated. The two metabolites M3A and M3B were diastereomers, but fully separated by HPLC. Here, oxidation of the aromatic CH carbon resulted in prototropic rearrangement to an αβ-unsaturated thiolactone. None of the three major metabolites of DMTA-P has been described before.

Batch vs continuous-feeding operational mode for the removal of pesticides from agricultural run-off by microalgae systems: A laboratory scale study

Microalgae-based water treatment technologies have been used in recent years to treat different water effluents, but their effectiveness for removing pesticides from agricultural run-off has not yet been addressed. This paper assesses the effect of microalgae in pesticide removal, as well as the influence of different operation strategies (continuous vs batch feeding). The following pesticides were studied: mecoprop, atrazine, simazine, diazinone, alachlor, chlorfenvinphos, lindane, malathion, pentachlorobenzene, chlorpyrifos, endosulfan and clofibric acid (tracer). 2L batch reactors and 5L continuous reactors were spiked to 10 μg L(-1) of each pesticide. Additionally, three different hydraulic retention times (HRTs) were assessed (2, 4 and 8 days) in the continuous feeding reactors. The batch-feeding experiments demonstrated that the presence of microalgae increased the efficiency of lindane, alachlor and chlorpyrifos by 50%. The continuous feeding reactors had higher removal efficiencies than the batch reactors for pentachlorobenzene, chlorpyrifos and lindane. Whilst longer HRTs increased the technology's effectiveness, a low HRT of 2 days was capable of removing malathion, pentachlorobenzene, chlorpyrifos, and endosulfan by up to 70%. This study suggests that microalgae-based treatment technologies can be an effective alternative for removing pesticides from agricultural run-off.

Carbazole hydroxylation by the filamentous fungi of the Cunninghamella species

Nitrogen heterocyclic compounds, especially carbazole, quinolone, and pyridine are common types of environmental pollutants. Carbazole has a toxic influence on living organisms, and the knowledge of its persistence and bioconversion in ecosystems is still not complete. There is an increasing interest in detoxification of hazardous xenobiotics by microorganisms. In this study, the ability of three filamentous fungi of the Cunninghamella species to eliminate carbazole was evaluated. The Cunninghamella elegans IM 1785/21Gp and Cunninghamella echinulata IM 2611 strains efficiently removed carbazole. The IM 1785/21Gp and IM 2611 strains converted 93 and 82 % of the initial concentration of the xenobiotic (200 mg L(-1)) after 120 h incubation. 2-Hydroxycarbazole was for the first time identified as a carbazole metabolite formed by the filamentous fungi of the Cunninghamella species. There was no increase in the toxicity of the postculture extracts toward Artemia franciscana. Moreover, we showed an influence of carbazole on the phospholipid composition of the cells of the tested filamentous fungi, which indicated its harmful effect on the fungal cell membrane. The most significant modification of phospholipid levels after the cultivation of filamentous fungi with the addition of carbazole was showed for IM 1785/21Gp strain.

Efficient alachlor degradation by the filamentous fungus Paecilomyces marquandii with simultaneous oxidative stress reduction

The acceleration of alachlor degradation by Paecilomyces marquandii under controlled and optimized conditions of fungal cultivation in liquid batches was observed (by ca. 20% in comparison to the flask cultures). Acidic environment and oxygen limitation resulted in deterioration of herbicide elimination. Efficient xenobiotic degradation did not correlate with free radicals formation, but some conditions of bioreactor cultivation such as neutral pH and oxygen enriched atmosphere (pO2⩾30%) caused a decrease in the reactive oxygen species (ROS) accumulation in mycelia. The changes in the glutathione (GSH) and ascorbic acid (AA) levels, also in the dismutase (SOD) and catalase (CAT) activities showed active response of the tested fungus against alachlor induced oxidative stress. These results will contribute to the improvement of chloroacetanilides elimination by fungi and extend the knowledge concerning oxidative stress induction and fungal cellular defense.

Biodegradation of nonylphenol by a novel entomopathogenic Metarhizium robertsii strain

The biodegradation of nonylphenol (NP) by a newly isolated form of the larva fungal strain Metarhizium robertsii IM 6519 was investigated in this study. This isolate was capable of degrading 4-n-NP, and multiple metabolites were detected. The coexistence of parallel degradation pathways with versatile hydroxylation in different positions of the alkyl chain is a unique feature of this strain. Moreover, several metabolites previously described only in higher eukaryotes were detected in the fungal cultures. The degradation process led to the mineralization of 4-n-NP (with an efficiency of 36%), a great advantage of this strain that results in complete removal of toxic substrate from the environment.

Mechanism study of alachlor biodegradation by Paecilomyces marquandii with proteomic and metabolomic methods

Alachlor is an herbicide that is widely used worldwide to protect plant crops against broadleaf weeds and annual grasses. However, due to its endocrine-disrupting activity, its application had been banned in the European Union. As described in our earlier work, Paecilomyces marquandii is a microscopic fungus capable of alachlor removal by N-acetyl oxidation. Our current work uses proteomics and metabolomics to gain a better understanding of alachlor biodegradation by the microscopic fungus P. marquandii. The data revealed that the addition of alachlor reduced the culture growth and glucose consumption rates. Moreover, the rates of glycolysis and the tricarboxylic acids (TCA) cycle increased during the initial stage of growth, and there was a shift toward the formation of supplementary materials (UDP-glucose/galactose) and reactive oxygen species (ROS) scavengers (ascorbate). Proteomic analysis revealed that the presence of xenobiotics resulted in a strong upregulation of enzymes related to energy, sugar metabolism and ROS production. However, the unique overexpression of cyanide hydratase in alachlor-containing cultures may implicate this enzyme as the key protein involved in the alachlor biodegradation pathway. The characterization of P. marquandii-mediated alachlor removal in terms of cell structure and function provides a deeper insight into the strategies of microorganisms toward xenobiotic biodegradation.