Rapid degradation of the organophosphate pesticide - Chlorpyrifos by a novel strain of Pseudomonas nitroreducens AR-3

Biodegradation of hydrophobic pesticides by microalgae: Transformation products and impact on algae biochemical methane potential

Intensive and extensive use of pesticides has contributed to their wide distribution in soil, air, and water. Due to their detrimental effects on non-target organisms, different technologies have been considered for their removal. In this work, three hydrophobic pesticide active compounds, namely, chlorpyrifos, cypermethrin, and oxadiazon, were selected to study the potential for their removal from aqueous media by a microalgae consortium. An abiotic and a killed control (thermally inactivated dead microalgae biomass) were employed to clarify their removal pathways, and pesticide content was quantified in liquid and biomass phases for 7 days. At the final time, total degradation (biodegradation plus photodegradation) contributed to the removal of 55% of oxadiazon, 35% of chlorpyrifos, and 14% of cypermethrin. Furthermore, more than 60% of chlorpyrifos and cypermethrin were removed by sorption onto microalgae biomass. Overall, the three pesticides showed high removal from the liquid phase. O,O-diethyl thiophosphate was identified in the liquid phase as a transformation product of chlorpyrifos formed by microalgae degradation. Phycoremediation was coupled with anaerobic degradation of the microalgae biomass containing the retained pesticides by sorption through biochemical methane potential tests. Anaerobic digestion was not inhibited by the pesticides as verified by methane production yields. The removal efficiency of the pesticides in the digestate was as follows: chlorpyrifos > cypermethrin > oxadiazon. These results highlight the potential of low-cost algal-based systems for the treatment of wastewater or effluents from agrochemical industries. The integration of wastewater treatment with biogas production through anaerobic digestion is a biorefinery approach that facilitates the economic feasibility of the process.

A treatise on Organophosphate pesticide pollution: Current strategies and advancements in their environmental degradation and elimination

Pesticides have been used in the field of agriculture ever since their role in protection of crops from pests which include four different categories namely insects, mites, rodents and animals has been identified. Organophosphate pesticides are one of the most extensively applied insecticides in the field of agriculture such that around 40% of all the pesticides that are produced and used commercially belong to this category. The main toxicological effect of these pesticides when exposed to a living being encompasses the irremediable inhibition of the acetylcholinesterase (AChE) enzyme which is involved in the neurotransmission of signals and hence its inhibition causes impairment of the respiratory tract and neuromuscular transmission. Apart from being used as a pesticide, organophosphates have also been applied as herbicides to some extent. The residues of these highly toxic chemicals have found route into the underground water system by seeping into the ground, in rivers where the agricultural run off water is disposed, and in the air when sprayed on the crops hence posing a threat to all the living strata exposed to these chemicals in various ways which are discussed further. Many significant studies have been carried out in order to evaluate the health risks associated with these pesticides which commonly include acute neurological disorders. This review emphasizes on the toxicological effects of organophosphate pesticides and the recent methods of detection that are used to identify trace amounts of organophosphate pesticides along with strategies which are used for their degradation.

A recent global review of hazardous chlorpyrifos pesticide in fruit and vegetables: Prevalence, remediation and actions needed

Pollution with pesticides is a widespread global problem and biomonitoring of the environment and human populations is necessary to assess potential harmful biological effects. One of the pesticides that are showing up in vegetables and fruit is chlorpyrifos (CPS). CPS is a nerve-poisoning organophosphorus insecticide, which is in up to 1/3 of all conventionally produced citrus fruits. Our review shows that CPS is a hazardous material that poses risks to human health and also pollutes the environment. There is numerous risk assessment of CPS reported, however, the assessment is easily affected by factors such as climate change, exposure period and CPS concentration. Therefore, rigorous update of the hazardous level of CPS is needed to determine the threshold level safe for humans and animals. There is a need for remediation using for example photoreactive nanoparticle methods and microbial degeneration possessing high degradation efficiency (73-97%). In addition, stringent biomonitoring of food, environment and human exposure should occur to avoid exposure to chemicals via citrus fruits and vegetables. This is necessary to assess health risks and socioeconomic impacts which also require collaboration between private and public sectors to facilitate the growth, sale and manufacturing of biopesticides.

Organophosphorus compounds biodegradation by novel bacterial isolates and their potential application in bioremediation of contaminated water

Organophosphorus compounds (OPs), the major pesticides used worldwide, comprise an environmental hazard due to their harmful toxicity. Aimed to develop a bioreactor to remediate OPs contaminated wastewater, bacteria isolated from contaminated soils were identified and their ability to degrade OPs assessed, resulting in two main isolates, Sphingomonas sp. and Brevundimonas sp. Their OP degrading activities were characterized in terms of temperature, pH and substrates acceptance, resulting in high degradation rates at 60 °C, pH 10 and towards bulky OPs such as coroxon, coumaphos, and chlorpyrifos. Sphingomonas sp. cells were immobilized and 75.4% degradation of 0.15 mM chlorpyrifos was achieved after 21 days by immobilized cells in batch system, while this OP was completely degraded within 17 h when the biocatalyst is settled in a packed bed bioreactor, with a reusability of 8 cycles. These results suggest the potential application of this system in the bioremediation of contaminated wastewater.

Unlocking the potential of plant growth-promoting rhizobacteria on soil health and the sustainability of agricultural systems

The concept of soil health refers to specific soil properties and the ability to support and sustain crop growth and productivity, while maintaining long-term environmental quality. The key components of healthy soil are high populations of organisms that promote plant growth, such as the plant growth promoting rhizobacteria (PGPR). PGPR plays multiple beneficial and ecological roles in the rhizosphere soil. Among the roles of PGPR in agroecosystems are the nutrient cycling and uptake, inhibition of potential phytopathogens growth, stimulation of plant innate immunity, and direct enhancement of plant growth by producing phytohormones or other metabolites. Other important roles of PGPR are their environmental cleanup capacities (soil bioremediation). In this work, we review recent literature concerning the diverse mechanisms of PGPR in maintaining healthy conditions of agricultural soils, thus reducing (or eliminating) the toxic agrochemicals dependence. In conclusion, this review provides comprehensive knowledge on the current PGPR basic mechanisms and applications as biocontrol agents, plant growth stimulators and soil rhizoremediators, with the final goal of having more agroecological practices for sustainable agriculture.

Symbiont-Mediated Insecticide Detoxification as an Emerging Problem in Insect Pests

Pesticide use is prevalent with applications from the backyard gardener to large-scale agriculture and combatting pests in homes and industrial settings. Alongside the need to control unwanted pests comes the selective pressure generated by sustained pesticide use has become a concern leading to environmental contamination, pest resistance, and, thus, reduced pesticide efficacy. Despite efforts to improve the environmental impact and reduce off-target effects, chemical pesticides are relied on and control failures are costly. Though pesticide resistance mechanisms vary, one pattern that has recently emerged is symbiont-mediated detoxification within insect pests. The localization within the insect host, the identity of the symbiotic partner, and the stability of the associations across different systems vary. The diversity of insects and ecological settings linked to this phenomenon are broad. In this mini-review, we summarize the recent trend of insecticide detoxification modulated by symbiotic associations between bacteria and insects, as well as highlight the implications for pesticide development, pest management strategies, and pesticide bioremediation.

Draft Genome Sequence of a Potential Organic Phosphorus-Degrading Bacterium Brevibacterium frigoritolerans GD44, Isolated from Radioactive Soil in Xinjiang, China

Brevibacterium frigoritolerans, a strain quite potential use in environmental pollution, is also able to degrade the pesticide phorate. Here, we report a strain isolated from radioactive soil in the Xinjiang Uygur Autonomous Region of China. The genome of strain GD44 encompasses 5,471,331 base pairs with a GC content of 40.42%. The sequence was assembled into 1985 open reading frames (ORFs) encoding 5053 proteins. Sequence analysis identified the genes encoding enzymes related to the degradation of organophosphorus compounds such as esterase, phosphotransferase, C-P lyase, and alkaline phosphatase. The nitrate reductase gene was also found in GD44, which was associated with biosynthesis of silver nanoparticles used for bacteriostat. In addition, Antibiotic Resistance Ontology (ARO) genes accounted for 10.6%, including the vancomycin resistance gene cluster. Therefore, the whole-genome sequence of B. frigoritolerans GD44 will be beneficial for identifying and analyzing genes utilized for soil remediation and antibacterial agent, which will provide genetic evaluation for potential application in the future.

Exploring the degradation capability of Trametes versicolor on selected hydrophobic pesticides through setting sights simultaneously on culture broth and biological matrix

Pesticides introduced inadvertently or deliberately into environment by global agricultural practices have caused growing public concern, therefore the search of approaches for elimination of such xenobiotics should be motivated. The degradation of hydrophobic pesticides including chlorpyrifos, dicofol and cypermethrin were assayed with the white-rot fungus Trametes versicolor. Experiments were set at realistic concentration as 5 μg L^-1, and both culture medium and biologic matrix were analyzed for pollutants residues. Results showed that the first step was due to a fast adsorption, which also played an important role, accounting for more than 90% removal in average. Then mass balances proposal evidenced the biodegradation of the adsorbed pollutants, demonstrating efficient depletion as 94.7%, 87.9% and 93.1%, respectively. Additionally, the related degradation metabolites were identified using ultra performance liquid chromatography coupled to high resolution mass spectrometry. Two compounds, namely O,O-diethyl thiophosphate and diethyl phosphate were detected as transformation products of chlorpyrifos, whereas dicofol was degraded into benzaldehyde that is first time to be reported. It also confirms the degradation capability of T. versicolor. Our results suggest that T. versicolor is a potential microorganism for bioremediation of hydrophobic pesticide contaminated environments.

Study on the characteristics and mechanisms of nicosulfuron biodegradation by Bacillus velezensis CF57

Nicosulfuron is one of the main sulfonylurea herbicides that have been widely used to protect maize crops. A total of 10 nicosulfuron-degrading strains were isolated from the intestine tract of earthworm Eisenia foetida. Among them, Bacillus velezensis CF57 with the highest degradation efficiency was selected and studied in detail. The degradation characteristics of CF57 showed that it was able to effectively degrade nicosulfuron in a wide range of temperature, pH, and a low inoculation amount, and the response surface analysis revealed that the optimum degradation conditions were 30.8 °C, pH 6.31, and inoculation amount 3.04%. Meanwhile, CF57 could degrade high-concentration nicosulfuron efficiently and posed a broad degradation spectrum of other sulfonylurea herbicides. Furthermore, the localization of degradation enzyme indicated that the nicosulfuron-degrading enzyme was an extracellular fraction. By analyzing the metabolites of nicosulfuron, it could be further determined that the degradation of nicosulfuron by strain CF57 was mainly through the extracellular enzyme, and its possible degradation pathway was mainly derived from the cleavage of the C-N bond of the sulfonylurea bridge. These results may provide new insights into bioremediation of nicosulfuron-contaminated environments and enrich the resources of degrading bacteria of sulfonylurea herbicides.

Rapid biodegradation of chlorpyrifos by plant growth-promoting psychrophilic Shewanella sp. BT05: An eco-friendly approach to clean up pesticide-contaminated environment

The present study explores the rapid chlopyrifos (CPs) biodegradation potential of plant growth promoting (PGP) psychrophilic bacteria isolated from brackish water by enrichment culture technique. Based on biochemical tests and 16 S rDNA sequencing the isolate was identified as Shewanella sp. The isolate Shewanella BT05 showed significant growth rate in various concentrations of (10-50 mg/L) CPs. The isolate produced plant growth promoting factors, IAA (20.8 ± 1.2 and 15.4 ± 1.0 μg/mL) and siderophores (60.67 ± 1.2 and 57.5 ± 0.9%) in the absence and presence of CPs. Further, the isolate BT05 solublized phosphate (16.5 ± 1.0 and 12.0 ± 1.0 mm in size respectively), and produce hydrogen cyanide (excellent and moderate) in the presence and absence of CPs. The isolate BT05 degraded 94.3, 91.8, 87.9, 82.6, and 80.5% of CPs at 10, 20, 30, 40, and 50 mg/L, respectively, within 24 h. Further, the media conditions were optimized for enhanced CPs removal and observed 93% removal in the presence of 3.5% glucose in pH 7.0 at 32.5 °C. Fourier-transform infrared spectroscopy and high-performance liquid chromatography results indicated the role for Shewanella BT05 in the biomineralization of CPs. The results suggested the isolate BT05 could be used for CPs removal as well as PGP activity in contaminated soil.

A critical review of different factors governing the fate of pesticides in soil under biochar application

Pesticides are extensively used in the modern agricultural system. The inefficient and extensive use of pesticides during the last 5 to 6 decades inadvertently led to serious deterioration of environmental quality with health risk to living organisms, including humans. It is important to use some environmentally-friendly and sustainable approaches to remediate, restore and maintain soil quality. Biochar has gained considerable attention globally as a promising soil amendment because it has the ability to adsorb and as such minimize the bioavailability of pesticides in soils. This review emphasizes the recent trends and implications of biochar in pesticide-contaminated soils, as well as highlights need of the pesticides use and associated environmental issues in context of the biochar application. The overarching aim of this review is to signify the role of biochar on primary processes such as effect of biochar on the persistence, mineralization, leaching and efficacy of pesticides in soil. Notably, the effects of biochar on pesticide adsorption-desorption, degradation and bioavailability under various operating/production conditions are critically discussed. This review delineates the indirect impact of biochar on pesticides persistence in soils and proposes key recommendations for future research which are essential for the remediation and restoration of pesticides-impacted soils.