Degradation Of Malathion Research Articles

Z-scheme H-PDI supermolecule/NH2-MIL-101(Fe) for enhanced malathion degradation: Mechanism, pathway, and toxicity assessment

Malathion (MA) is a widely used organophosphorus pesticide globally. Developing efficient photocatalysts is crucial for eliminating MA pollution in water by photocatalytic technology. This study focuses on preparing a series of H-PDI supermolecule/NH2-MIL-101(Fe) (PM) materials by amidating NH2-MIL-101(Fe) with the more stable H-PDI supermolecule, forming a covalent OC–NH bond. Among these materials, 40 %PM (indicating a mass percentage content of 40 % H-PDI supermolecule in PM) exhibited the best performance for degradation of MA. Under simulated sunlight irradiation of a 10 mg·L1 MA solution for 180 min, the reaction rate constants of 40 %PM were 5.95 times and 3.13 times higher than those of NH2-MIL-101(Fe) and H-PDI supermolecule, respectively. The enhanced performance is attributed to the formation of Z-scheme heterojunctions in the 40 %PM composite lead to fast separation of photogenerated e− and h+. Combining the results of HPLC-MS with Fukui Function, the HOMO, LUMO, and pathway of degradation of MA attracted by 1O2, •OH, and h+ were speculated. The pathway involves oxidation, demethylation, P-S bond breakage, decarboxylation, and final conversion to some inorganic molecules. The toxicity of the degradation byproducts were lower than that of MA estimated by Toxicity Estimation Software Tool.

Green synthesis of TiO2@g-C3N4 nanocomposites for the photocatalytic degradation of pesticides and toxic organics present in water and wastewater

To address the environmental challenges caused by toxic organics in aquatic systems, photocatalytic degradation is a promising option. This study investigates the green synthesis of TiO2@g-C3N4 nanocomposites by coupling Titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) in different mass ratios through solvothermal technique due to their photocatalytic properties. Leaf extract from the Ziziphus jujube plant was utilized as a green template making the synthesis environmentally friendly, utilizing renewable resources, and employing facile and cost-effective methods. The nanocomposites were characterized using various analytical techniques including UV–Vis Diffuse reflectance spectroscopy (UV–Vis DRS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectroscopy (EDS) to analyze the structural and morphological properties. The wavelength ranged from 385 to 454 nm and band gap energies ranged from 3.22 to 2.73 eV for the synthesized materials. The pure green TiO2 showed the highest band gap energy while pure g-C3N4 showed the lowest band gap energy among the synthesized materials. The photocatalytic activity of the synthesized nanocomposites was evaluated through the degradation of Bisphenol A and Malathion pesticide under UV light irradiation. The results indicated 71 % degradation of Bisphenol A with the 50 % TiO2@g-C3N4 nanocomposites exhibiting 1.422 x 10-2 min−1 rate constant and 74 % degradation of Malathion degraded over 20 % TiO2@g-C3N4 which depicted rate kinetics of 1.022 x 10-2 min−1. Moreover, both showcased higher performance than the individual TiO2 and g-C3N4 nanostructured materials.

Combined metabolomics and proteomics to reveal the mechanism of S. oneidensis MR-1 degradation malathion enhanced by FeO/C

Iron oxide @ biochar (FeO/C) promotes bacterial growth and facilitates electron transfer, thereby effectively promoting malathion degradation by Shewanella oneidensis MR-1 (S. oneidensis MR-1). This study elucidated the underlying mechanism of FeO/C-enhanced malathion degradation by S. oneidensis MR-1 through a combination of metabolomics and proteomics analysis. The kinetic fitting results from the degradation experiment indicated that 0.1 g/L FeO/C exerted the most significant enhancement effect on malathion degradation by S. oneidensis MR-1. Observations from Scanning Electron Microscopy and Laser Scanning Confocal Microscopy, along with physiological and biochemical analysis, showed that FeO/C enhanced the growth and oxidative response of S. oneidensis MR-1 under malathion stress. In addition, metabolomics and proteomics analysis revealed an increase in certain electron transfer related metabolites, such as coenzymes, and the upregulation of proteins, including coenzyme A, sdhD, and petC. Overall, spectroscopic analysis suggested that Fe2+, which was reduced from Fe3+ by S. oneidensis MR-1 in FeO/C, promoted electron transfer in S. oneidensis MR-1 to enhance the degradation of malathion. This study offers enhanced strategies for efficient removal of malathion contaminants.

Ecotoxicological strategies employing biochemical markers and organisms to monitor the efficacy of malathion photolysis treatment

The objective of this study was to assess the photolysis-mediated degradation of malathion in standard and commercial formulations, and to determine the toxicity of these degraded formulations. Degradation tests were carried out with 500 μg L−1 of malathion and repeated three times. The initial and residual toxicity was assessed by using Lactuca sativa seeds for phytotoxicity, Stegomyia aegypti larvae for acute toxicity, and Stegomyia aegypti mosquitoes (cultivated from the larval stage until emergence as mosquitoes) to evaluate the biochemical markers of sublethal concentrations. For the standard formulations the photolytic process efficiently reduced the initial concentration of malathion to levels below the regulatory limits however, the formation of byproducts was revealed by chromatography, which allowed for a more complete proposal of photolytic-mediated malathion degradation route. The degraded formulations inhibited the growth of L. sativa seeds, while only the untreated formulations showed larvicidal activity and mortality. Both formulations slightly inhibited acetylcholinesterase activity in S. aegypti mosquitoes, while the standard formulation decreased and the commercial formulation increased glutathione S-transferase activity. However, there were no significant differences for superoxide dismutase, esterase-α, esterase-β and lipid peroxidation. These findings indicate that in the absence of the target compound, the presence of byproducts can alter the enzymatic activity. In general, photolysis effectively degrade malathion lower than the legislation values; however, longer treatment times must be evaluated for the commercial formulation.

Study on stability improvement measures of malathion in different matrices

ABSTRACTMalathion was unstable in many matrices due to its unique structure and physicochemical properties. This study aimed to investigate the storage stability of malathion in a range of products, including cabbage, tomato, lettuce, potato, carrot, grape, and orange. The research sought to elucidate the contributing factors and strategies to enhance malathion’s stability. Significant reduction of malathion was found over time due to the different storage conditions and the properties of the matrices. The results showed that lower temperature could better store samples. The influence of storage form displayed that homogenised form was more stable than coarse form for cabbage, lettuce, grape and orange. Malathion had the worst stability in potato and carrot. This seemed to be attributed to some special substance in high starch crops that promoted rapid degradation of malathion. When pH was adjusted to 3, the residue in cabbage was basically increased to a stable level. Moreover, methanol and dichloromethane could effectively improve the stability of malathion in cabbage, the mass ratio of sample to dichloromethane of 10:1 was better than that of 25:1. Therefore, the selection of appropriate storage conditions and forms, and the incorporation of exogenous additives could offer practical options to improve malathion stability in various matrices.

Biodegradation of Malathion in Amended Soil by Indigenous Novel Bacterial Consortia and Analysis of Degradation Pathway

The capabilities of pure bacterial strains and their consortia isolated from agricultural soil were evaluated during a bioremediation process of the organophosphate pesticide malathion. The pure bacterial strains efficiently degraded 50.16–68.47% of the pesticide within 15 days of incubation, and metabolites were observed to accumulate in the soil. The consortia of three bacterial species [Micrococcus aloeverae (MAGK3) + Bacillus cereus (AGB3) + Bacillus paramycoides (AGM5)] degraded the malathion more effectively, and complete malathion removal was observed by the 15th day in soils inoculated with that consortium. In contrast, the combined activity of any two of these strains was lower than the mixed consortium of all of the strains. Individual mixed consortia of Micrococcus aloeverae (MAGK3) + Bacillus cereus (AGB3); Micrococcus aloeverae (MAGK3) + Bacillus paramycoides (AGM5); and Bacillus cereus (AGB3) + Bacillus paramycoides (AGM5) caused 76.58%, 70.95%, and 88.61% malathion degradation in soil, respectively. Several intermediate metabolites like malaoxon, malathion monocarboxylic acid, diethyl fumarate, and trimethyl thiophosphate were found to accumulate and be successively degraded during the bioremediation process via GC–MS detection. Thus, inoculating with a highly potent bacterial consortium isolated from in situ soil may result in the most effective pesticide degradation to significantly relieve soils from pesticide residues, and could be considered a prospective approach for the degradation and detoxification of environments contaminated with malathion and other organophosphate pesticides. This study reports the use of a mixed culture of Indigenous bacterial species for successful malathion degradation.

Highly efficient and rapid removal of Malathion using non-aerated algae bacteria consortia: Performance, kinetic, and microbial mechanisms

The frequent use of pesticides in human activities introduce Malathion into water， which caused serious environmental pollutants. However, the treatment of these wastewaters is expensive and inefficiency. In this study, two photo-sequencing batch reactors (PSBRs) were established to treat Malathion-containing wastewater using algae bacteria consortia (ABC) in aerated (R1) and non-aerated (R2) conditions, respectively. The removal rates of Malathion by ABC in R1 and R2 after stabilization were 83.6 % and 71.9 %, respectively. The microbial community analysis results indicated that Burkholderia was the dominant population in ABC, which was response for the main Malathion degradation. Furthermore, the investigation of degradation pathways of Malathion discovered that the ABC converted Malathion into inorganic phosphorus. The conversion rates of inorganic phosphorus in the two reactors were 16.9 % and 21.6 %. The results demonstrated that non-aerated ABC have a strong potential adaption on Malathion stress and can removal Malathion from wastewater economically and efficiently.

The overlooked role of UV185 induced high-energy excited states in the dephosphorization of organophosphorus pesticide by VUV/persulfate

Vacuum ultraviolet (VUV) based advanced oxidation processes (AOPs) recently attracted widespread interests. However, the role of UV185 in VUV is only considered to be generating a series of active species, while the effect of photoexcitation has long been overlooked. In this work, the role of UV185 induced high-energy excited state for the dephosphorization of organophosphorus pesticides was studied using malathion as a model. Results showed malathion degradation was highly related to radical yield, while its dephosphorization was not. It was UV185 rather than UV254 or radical yield that was responsible for malathion dephosphorization by VUV/persulfate. DFT calculation results demonstrated that the polarity of P-S bond was further increased during UV185 excitation, favoring dephosphorization while UV254 did not. The conclusion was further supported by degradation path identification. Moreover, despite the fact that anions (Cl-, SO42- and NO3-) considerably affected radical yield, only Cl- and NO3- with high molar extinction coefficient at 185 nm significantly affected dephosphorization. This study shed light on the crucial role of excited states in VUV based AOPs and provided a new idea for the development of mineralization technology of organophosphorus pesticides.

Catalytic activity of Mn(III) porphyrin complex supported onto cross linked polymers in the green oxidation of malathion with hydrogen peroxide in aqueous solution

Developing effective, affordable, and recoverable heterogeneous catalysts is one of the foremost challenges in modern chemistry. Mn(III) complexes of 5-(4-aminophenyl) −10, 15, and 20-triphenyl porphyrin 1 immobilized covalently on polymethyl methacrylate (PMMA) 2 and poly(methyl methacrylate –co- styrene) (PMMA/ST) 3 were synthesized, characterized, and applied for degradation of malathion with H2O2 in aqueous solution. Mn(III) porphyrin complex anchored on cross linked polymers 4 and 5 show high catalytic activity for malathion (pesticide) degradation in an aqueous solution with green oxidant H2O2. The catalytic efficacy of malathion degradation was highest with the Mn(III) porphyrin complex covalently anchored on (polymethyl methacrylate-co-styrene) 5. The optimum conditions, including the effect of pH, catalyst concentration, and H2O2 concentration on the degradation of malathion, were investigated. The reuse and stability of catalysts were examined, and the findings proposed that the Mn(III) porphyrin complex 5 has no noticeable changes in the removal efficiency up to five consecutive cycles. GC–MS analyses showed that the degraded compounds and intermediates formed from malathion degradation were non-toxic to E. coli bacteria. For the degradation of dissolved malathion pesticides in an aqueous solution, the use of Mn(III) porphyrin complex 5 in the presence of H2O2 has the potential to be advantageous.

Preparation of chabazite based Fenton-like heterogeneous catalyst and its organic micropollutant removal performance

Natural chabazite (CHA) is used for the first time as a heterogeneous catalyst in Fenton-like oxidation. Pretreatment techniques (NH4+-exchange, steam treatment, and Fe-exchange) were applied to natural CHA to improve the available micropore and mesopore volume as well as to increase Fe-content. CHA samples were characterized by XRD, N2 adsorption, UV–Vis, SEM-EDX, ICP-OES, and MAS NMR to study the improvement after each pretreatment. Steam treatment at 675 °C and 20 kPa improved the mesopore volume of CHA, which enabled Fe3+ concentration to increase from 0.24 to 0.60 mmol Fe3+ g CHA−1 following the Fe-exchange. The Fe-exchanged CHA (Fe-CHA) was then tested for malathion oxidation. The effect of H2O2 and catalyst doses and pH on the degradation of malathion was investigated. Fenton-like oxidation was realized at a higher and wider pH range (pH 3–7) when compared to classical Fenton. A malathion removal between 20 and 81% was achieved depending on the initial malathion concentration (250–750 μg L−1), Fenton Reagents (H2O2 and Fe-CHA) concentrations (75–300 mg L−1 and 250–750 mg L−1, respectively) and pH (3–7). The metabolites of malathion were identified as malaoxon, desmethyl malaoxon and diethyl malate. A possible oxidation pathway was proposed, where desmethyl malaoxon and diethyl malate were identified as the secondary oxidation products. Moreover, the performance of Fe-CHA was compared with commercially available synthetic zeolites of Fe-Ultra-stable Y and Fe-ZSM-5. Fe-CHA is found to be comparably effective as these synthetic zeolites, as well as providing substantially smaller sludge production when compared to classical Fenton.

Accelerated degradation of groundwater-containing malathion using persulfate activated magnetic Fe3O4/graphene oxide nanocomposite for advanced water treatment

Malathion (MT) is a widely used organophosphate insecticide with a broad spectrum. MT residues in the environment even at low concentrations can have adverse effects on humans, plants, animals, and ecosystems. In this study aimed to investigate the MT degradation yield from groundwater using persulfate activated magnetic Fe3O4/graphene oxide nanocomposite (PS/Fe3O4-GO MNCs). Thus, the effects of MT concentration, the dosage of PS and Fe3O4-GO MNCs, pH value along with reaction time were investigated and further optimized applying Response Surface Method (RSM). This model equation showed a sufficient match with the measured results from the experimental data with the correlation coefficient (R2) of 0.9819 according to the analysis of variance. For the optimal yield, MT concentration of 3.7 mg/L, PS of 2.25 mM, Fe3O4-GO MNCs dosage of 225 mg/L, reaction time of 22 min and pH of 4 were obtained. Moreover, for MT degradation, the estimated optimal degradation efficiency was 96.5 %. Furthermore, a distinct synergistic effect was observed upon the usage of Fe3O4-GO MNCs for PS activation. The MT degradation rate is generally characterized by a pseudo-first-order kinetic model. Besides, experiments with radical scavengers revealed that both OH∙ and SO4-∙radicals had significant functions in MT degradation yields, with sulphate radicals being the dominant species. Conclusively, results revealed that the PS/Fe3O4-GO MNCs degradation process is an effective method for remediating waters that have been polluted with MT and related pesticides.

Photocatalytic activity of graphene oxide-TiO2 nanocomposite on dichlorvos and malathion and assessment of toxicity changes due to photodegradation

Heterogeneous photocatalysis was used for the removal of two widely used organophosphorus pesticides, dichlorvos, and malathion from water. Graphene oxide-TiO2 nanocomposite (GOT) was synthesized and used as a photocatalyst for the removal of these pesticides. Batch studies for optimizing photocatalytic degradation and mineralization of pesticides over 80 min were conducted by varying the pH (2–10), catalyst dose (20 mg/L-200 mg/L), and initial pesticide concentration (0.5 mg/L-20 mg/L), and the irradiation source (125 W UV and visible lamp). Degradation kinetics for the pesticides were evaluated. Ellman assay was used to estimate the toxic effect of pesticides and evaluate toxicity reduction due to treatment. The highest degradation and mineralization of dichlorvos and malathion was observed at pH 6 and the optimum catalyst dose was 60 mg/L. Under UV irradiation, 80% and 90% degradation were observed for dichlorvos and malathion, respectively for 0.5 mg/L initial pesticide concentration. The photocatalytic degradation reaction followed Langmuir-Hinshelwood kinetics. A high degree of mineralization was achieved for both the pesticides. Analysis of the results revealed that the residual toxic effect after photocatalysis was primarily due to the residual parent compound. A comparative study revealed that GOT yielded better pesticide degradation compared to commercially available TiO2 under both UV and visible irradiation.

Isolation and Identification of Efficient Malathion-Degrading Bacteria from Deep-Sea Hydrothermal Sediment.

The genetic and metabolic diversity of deep-sea microorganisms play important roles in phosphorus and sulfur cycles in the ocean, distinguishing them from terrestrial counterparts. Malathion is a representative organophosphorus component in herbicides, pesticides, and insecticides and is analogues of neurotoxic agent. Malathion has been one of the best-selling generic organophosphate insecticides from 1980 to 2012. Most of the sprayed malathion has migrated by surface runoff to ocean sinks, and it is highly toxic to aquatic organisms. Hitherto, there is no report on bacterial cultures capable of degrading malathion isolated from deep-sea sediment. In this study, eight bacterial strains, isolated from sediments from deep-sea hydrothermal regions, were identified as malathion degradators. Two of the tested strains, Pseudidiomarina homiensis strain FG2 and Pseudidiomarina sp. strain CB1, can completely degrade an initial concentration of 500 mg/L malathion within 36 h. Since the two strains have abundant carboxylesterases (CEs) genes, malathion monocarboxylic acid (MMC α and MMC β) and dibasic carboxylic acid were detected as key intermediate metabolites of malathion degradation, and the pathway of malathion degradation between the two strains was identified as a passage from malathion monocarboxylic acid to malathion dicarboxylic acid.

Hierarchical Nanoflowers of MgFe2O4, Bentonite and B-,P- Co-Doped Graphene Oxide as Adsorbent and Photocatalyst: Optimization of Parameters by Box-Behnken Methodology.

In the present study, nanocomposites having hierarchical nanoflowers (HNFs) -like morphology were synthesized by ultra-sonication approach. HNFs were ternary composite of MgFe2O4 and bentonite with boron-, phosphorous- co-doped graphene oxide (BPGO). The HNFs were fully characterized using different analytical tools viz. X-ray photoelectron spectroscopy, scanning electron microscopy, energy dispersion spectroscopy, transmission electron microscopy, X-ray diffraction, vibrating sample magnetometry and Mössbauer analysis. Transmission electron micrographs showed that chiffon-like BPGO nanosheets were wrapped on the MgFe2O4-bentonite surface, resulting in a porous flower-like morphology. The red-shift in XPS binding energies of HNFs as compared to MgFe2O4-bentoniteand BPGO revealed the presence of strong interactions between the two materials. Box–Behnken statistical methodology was employed to optimize adsorptive and photocatalytic parameters using Pb(II) and malathion as model pollutants, respectively. HNFs exhibited excellent adsorption ability for Pb(II) ions, with the Langmuir adsorption capacity of 654 mg g−1 at optimized pH 6.0 and 96% photocatalytic degradation of malathion at pH 9.0 as compared to MgFe2O4-bentonite and BPGO. Results obtained in this study clearly indicate that HNFs are promising nanocomposite for the removal of inorganic and organic contaminants from the aqueous solutions.

Biodegradation of malathion by Micrococcus sp. strain MAGK3: kinetics and degradation fragments.

Malathion is widely used as an agricultural insecticide, but its toxic nature makes it a serious environmental contaminant. To screen indigenous bacteria for malathion degradation, a strain MAGK3 capable of utilizing malathion as its sole carbon and energy source was isolated from Pennisetum glaucum agricultural soil. Based on morphological and biochemical characteristics and 16S rDNA sequence analysis, strain MAGK3 was identified as Micrococcus aloeverae. The strain was cultured in the presence of malathion under aerobic and energy-restricting conditions, and it grew well in MSM containing malathion (1000µl/L), showing the highest specific growth rate at 500µl/L. Reverse-phase UHPLC-DAD analysis indicated that 100%, 90.48%, 84.27%, 75.46%, 66.65%, and 31.96% of malathion were degraded within 15days in liquid culture augmented with 50, 100, 200, 300, 500, and 1000µl/L concentrations of commercial malathion, respectively. Confirmation of malathion degradation to malathion mono, diacids, and phosphorus moiety was performed by Q-TOF-MS analysis, and a pathway of biodegradation was proposed. The influence of co-substrates was also examined to optimize biodegradation further. Kinetic studies based on different models were conducted, and the results demonstrated good conformity with the first-order model. Malathion degradation process by Micrococcus aloeverae was characterized by R2 of 0.95, and the initial concentration was reduced by 50% i.e. (DT50) in 8.11 d at an initial concentration of 500µl/L. This establishes the Micrococcus sp. as a potent candidate for active bioremediation of malathion in liquid cultures as it can withstand high malathion load and can possibly impact the development strategies of bioremediation for its elimination.

Degradation of malathion and carbosulfan by ozone water and analysis of their by-products.

Treatment by ozone water is an emerging technology for the degradation of pesticide residues in vegetables. The ozone dissolved in water generates hydroxyl radicals (· OH), which are highly effective in decomposing organic substances, such as malathion and carbosulfan. We found that washing pak choi with 2.0mg L-1 ozone water for 30 min resulted in 58.3% and 38.2% degradation of the malathion and carbosulfan contents respectively, and the degradation rates of these pure pesticides were 83.0% and 66.3% respectively. In addition, the 'first + first'-order reaction kinetic model was found to predict the trend in the pesticide content during ozone water treatment. Based on investigations by gas chromatography-mass spectrometry combined with the structures of the pesticides, the by-products generated were identified. More specifically, the ozonation-based degradation of carbosulfan generated carbofuran and benzofuranol, whereas malathion produced succinic acid and phosphoric acid. Although some new harmful compounds were formed during degradation of the parent pesticides, these were only present in trace quantities and were transient intermediates that eventually disappeared during the reaction. Our results, therefore, indicate that ozone water treatment technology for pesticide residue degradation is worthy of popularization and application. © 2022 Society of Chemical Industry.

Optimizing the malathion degrading potential of a newly isolated Bacillus sp. AGM5 based on Taguchi design of experiment and elucidation of degradation pathway

Malathion, a pesticide used to control pests in crops, vegetables, fruits, and livestock. Its widespread and indiscriminate usage has ensued in different ecological issues, thus, it's vital to remediate this insecticide. Malathion degrading bacterium Bacillus sp. AGM5, isolated from pesticide contaminated agricultural field was cultured in presence of different malathion concentrations under aerobic and energy restrictive conditions and was found effective at malathion degradation. Recovered malathion was extracted based on QuEChERS approach and then analyzed by UHPLC. About 39.5% of malathion biodegradation was observed at 300µlL-1 after 96h of incubation with the tested bacteria which increased to 58.5% and 72.5% after 240, and 360h of incubation, respectively. To further enhance malathion biodegradation, the effects of co-substrates, pH, temperature, initial malathion concentration, agitation (rpm), and inoculum size were evaluated using Taguchi methodology. Taguchi DOE's ability to predict the optimal response was established experimentally via optimised levels of these factors (glucose-0.1%, yeast extract-0.1%, inoculum size-2%wv-1, malathion concentration 300 µlL-1, rpm-150, pH-7, temperature 40°C), whereby biodegradation rate was enhanced to 95.49% after 38h. Confirmation of malathion biodegradation was performed by UHPLC, Q-TOF-MS, GC-MS analysis and a possible degradation pathway was proposed for malathion biodegradation. First order kinetic model was appropriate to describe malathion biodegradation. The Taguchi DOE proved to be viable tool for optimizing culture conditions and analysing the interactions between process parameters in order to attain the best feasible combination for maximum malathion degradation. These results could influence the development of a bioremediation strategy.

Optimization of process parameters for biodegradation of malathion by Micrococcus aloeverae MAGK3 using Taguchi methodology and metabolic pathway analysis

In this study, a previously isolated bacterial strain, Micrococcus sp. MAGK3 was employed to explore its malathion biodegradation potential. A considerable degradation (66.79%) was attained with malathion (0.03%) being the sole carbon source after 240 h of incubation. To enhance malathion biodegradation, effects of co-substrates, pH, temperature, initial malathion concentration, agitation (rpm), and inoculum size were evaluated using Taguchi methodology. Experiments with various combinations of factors were conducted, and results in respect of malathion biodegradation were evaluated in the Qualitek-4 software to determine the key effect of individual factors, their interaction effects, and optimal levels of process factors. All parameters contributed to malathion biodegradation, and Taguchi DOE's ability to predict optimum response, was established by experimentation via optimized levels of factors (carbon source 0.1%, nitrogen source 0.1%, pH 7, temperature 35 °C, pesticide concentration 0.03%, agitation 150 rpm, and inoculum size 2%(w/v). Results confirmed that pesticide concentration caused the maximum impact (34.09%) on malathion degradation followed by nitrogen source (32.11%), temperature (20.99%), RPM (6.55%), inoculum size (3.26%), carbon source (2.81%) and pH (0.2%). Before optimization, Micrococcus sp. MAGK3 had an average degradation of 57.94% within 168 h, but after optimization, the rate of biodegradation improved to 87% within 38 h. Confirmation of malathion biodegradation was performed by UHPLC, and GC-MS analysis and a possible degradation pathway was proposed for malathion biodegradation by Micrococcus sp. MAGK3. For the time being, this is the first publication to employ the Taguchi design of experiment to optimize the degradation of malathion by Micrococcus sp. MAGK3.

Towards a comprehensive understanding of malathion degradation: comparison of degradation reactions under alkaline and radical conditions.

Malathion is a commercially available insecticide that functions by acting as an acetylcholinesterase inhibitor. Of significant concern, if left in the environment, some of the products observed from the degradation of malathion can function as more potent toxins than the parent compound. Accordingly, there are numerous studies revolving around possible degradation strategies to remove malathion from various environmental media. One of the possible approaches is the degradation of malathion by OH˙ radicals which could be produced from both artificial and biological means in the environment. While there is plenty of evidence that OH˙ does in fact degrade malathion, there is little understanding of the underlying mechanism by which OH˙ reacts with malathion. Moreover, it is not known how competitive the radical degradation pathway is with analogous alkaline degradation pathways. Even less is known about the reaction of additional OH˙ radicals with the degradation byproducts themselves. Herein, we demonstrate that OH˙ induced degradation pathways have variable competitiveness with OH- driven degradation pathways and, in some cases, produce quite different reactivity.

Color-coded detection of malathion based on enzyme inhibition with dark-field optical microscopy

Malathion is widely applied in agriculture as one of organophosphorus pesticides (OPs) and easily causes a number of health and environmental problems. Traditional methods for analyzing malathion residues have failed to meet the current requirements of detection. To address this challenge, we designed a colorimetric-based single particle detection (SPD) method to quantify malathion using MnO2-coated gold nanoparticles (GNP@MnO2 NPs) as the probe. In the existence of alkaline phosphatase (ALP), p-aminophenyl phosphate (p-APP) can be hydrolyzed to p-aminophenol (p-AP), which employs as a reductant to induce MnO2 to Mn2+ and make the gold core exposure. With the dark field optical microscopy (DFM), the color change of the probe can be readily observed at the single particle level. However, malathion is able to inhibit the activity of ALP and makes the color of the probe remain. Thus, the content of malathion can be accurately quantified by monitoring the changes in color and scattering intensity of the probe. The linear range of this assay is 0.001–0.1 ng/mL and the limit of detection (LOD) is as low as 0.82 pg/mL. In addition, degradation of malathion can be achieved due to the interaction between malathion and ALP. Therefore, this strategy offers new insights on the design of an ultrasensitive assay for OPs detection and degradation in the future.