Biodegradation and rapid removal of methyl parathion by the paddy field cyanobacterium Fischerella sp

Biosorption Ability of Pharmaceutically Active Compounds by Anabaena sp. and Chroococcidiopsis thermalis

Drug overuse harms the biosphere, leading to disturbances in ecosystems' functioning. Consequently, more and more actions are being taken to minimise the harmful impact of xenopharmaceuticals on the environment. One of the innovative solutions is using biosorbents-natural materials such as cells or biopolymers-to remove environmental pollutants; however, this focuses mainly on the removal of metal ions and colourants. Therefore, this study investigated the biosorption ability of selected pharmaceuticals-paracetamol, diclofenac, and ibuprofen-by the biomass of the cyanobacteria Anabaena sp. and Chroococcidiopsis thermalis, using the LC-MS/MS technique. The viability of the cyanobacteria was assessed by determining photosynthetic pigments in cells using a UV-VIS spectrophotometer. The results indicate that both tested species can be effective biosorbents for paracetamol and diclofenac. At the same time, the tested compounds did not have a toxic effect on the tested cyanobacterial species and, in some cases, stimulated their cell growth. Furthermore, the Anabaena sp. can effectively biotransform DCF into its dimer.

Harnessing the potential of microalgae-based systems for mitigating pesticide pollution and its impact on their metabolism

Due to increased pesticide usage in agriculture, a significant concentration of pesticides is reported in the environment that can directly impact humans, aquatic flora, and fauna. Utilizing microalgae-based systems for pesticide removal is becoming more popular because of their environmentally friendly nature, ability to degrade pesticide molecules into simpler, nontoxic molecules, and cost-effectiveness of the technology. Thus, this review focused on the efficiency, mechanisms, and factors governing pesticide removal using microalgae-based systems and their effect on microalgal metabolism. A wide range of pesticides, like atrazine, cypermethrin, malathion, trichlorfon, thiacloprid, etc., can be effectively removed by different microalgal strains. Some species of Chlorella, Chlamydomonas, Scenedesmus, Nostoc, etc., are documented for >90% removal of different pesticides, mainly through the biodegradation mechanism. The antioxidant enzymes such as ascorbate peroxidase, superoxide dismutase, and catalase, as well as the complex structure of microalgae cell walls, are mainly involved in eliminating pesticides and are also crucial for the defense mechanism of microalgae against reactive oxygen species. However, higher pesticide concentrations may alter the biochemical composition and gene expression associated with microalgal growth and metabolism, which may vary depending on the type of strain, the pesticide type, and the concentration. The final section of this review discussed the challenges and prospects of how microalgae can become a successful tool to remediate pesticides.

Regulating pathway for bacterial diversities toward improved ecological benefits of thiencarbazone-methyl·isoxaflutole application: A field experiment

Herbicide abuse has a significantly negative impact on soil microflora and further influences the ecological benefit. The regulating measures and corresponding mechanisms mitigating the decreased bacterial diversity due to herbicide use have rarely been studied. A field experiment containing the application gradient of an efficient maize herbicide thiencarbazone-methyl·isoxaflutole was performed. The relationship between soil bacterial community and thiencarbazone-methyl·isoxaflutole use was revealed. Modified attapulgite was added to explore its impacts on soil microflora under the thiencarbazone-methyl·isoxaflutole application. Based on the analytic network process-entropy weighting method-TOPSIS method model, the ecological benefit focusing on microbial responses was quantitatively estimated along with technical effectiveness and economic benefit. The results showed that the diversity indices of soil microflora, especially the Inv_Simpson index, were reduced at the recommended, 5 and 10 times the recommended dosages of thiencarbazone-methyl·isoxaflutole use. The Flavisolibacter bacteria was negatively correlated with the residues in soils based on the random forest model and correlation analysis, indicating a potential degrader of thiencarbazone-methyl·isoxaflutole residues. The structural equation model further confirmed that the high soil water content and soil pH promoted the function of Flavisolibacter bacteria, facilitated the dissipation of thiencarbazone-methyl·isoxaflutole residues and further improved the diversity of soil microflora. In addition, the presence of modified attapulgite was found to increase the soil pH, which may improve bacterial diversity through the regulating pathway. This explained the high ecological benefits of the treatment where the thiencarbazone-methyl·isoxaflutole was applied at the recommended dosage rates in conjunction with modified attapulgite addition. Therefore, the comprehensive benefits of thiencarbazone-methyl·isoxaflutole application with a focus on ecological benefits can be improved by regulating the soil pH with modified attapulgite.

Microalgal-based bioremediation of emerging contaminants: Mechanisms and challenges

Emerging contaminants (ECs) in different ecosystems have consistently been acknowledged as a global issue due to toxicity, human health implications, and potential role in generating and disseminating antimicrobial resistance. The existing wastewater treatment system is incompetent at eliminating ECs since the effluent water contains significant concentrations of ECs, viz., antibiotics (0.03-13.0 μg L-1), paracetamol (50 μg L-1), and many others in varying concentrations. Microalgae are considered as a prospective and sustainable candidate for mitigating of ECs owing to some peculiar features. In addition, the microalgal-based processes also offer cost and energy-efficient solutions for the bioremediation of ECs than conventional treatment systems. It is pertinent that, microalgal-based processes also provides waste valorization benefits as microalgal biomass obtained after ECs treatment can be potentially applied to generate biofuels. Moreover, microalgae can effectively utilize alternative metabolic (cometabolism) routes for enhanced degradation of ECs. Additionally, the ECs removal via the microalgal biodegradation route is highly promising as it can transform the ECs into less toxic compounds. The present review comprehensively discusses different mechanisms involved in removing ECs and various factors that affect their removal. Also, the technoeconomic feasibility of microalgae than other conventional wastewater treatment methods is summarised. The review also highlighted the different molecular and genetic tools that can augment the activity and robustness of microalgae for better removal of organic contaminants. Finally, we have summarised the challenges and future research required towards microalgal-based bioremediation of emerging contaminants (ECs) as a holistic approach.

Microbiology and Biochemistry of Pesticides Biodegradation

Pesticides are chemicals used in agriculture, forestry, and, to some extent, public health. As effective as they can be, due to the limited biodegradability and toxicity of some of them, they can also have negative environmental and health impacts. Pesticide biodegradation is important because it can help mitigate the negative effects of pesticides. Many types of microorganisms, including bacteria, fungi, and algae, can degrade pesticides; microorganisms are able to bioremediate pesticides using diverse metabolic pathways where enzymatic degradation plays a crucial role in achieving chemical transformation of the pesticides. The growing concern about the environmental and health impacts of pesticides is pushing the industry of these products to develop more sustainable alternatives, such as high biodegradable chemicals. The degradative properties of microorganisms could be fully exploited using the advances in genetic engineering and biotechnology, paving the way for more effective bioremediation strategies, new technologies, and novel applications. The purpose of the current review is to discuss the microorganisms that have demonstrated their capacity to degrade pesticides and those categorized by the World Health Organization as important for the impact they may have on human health. A comprehensive list of microorganisms is presented, and some metabolic pathways and enzymes for pesticide degradation and the genetics behind this process are discussed. Due to the high number of microorganisms known to be capable of degrading pesticides and the low number of metabolic pathways that are fully described for this purpose, more research must be conducted in this field, and more enzymes and genes are yet to be discovered with the possibility of finding more efficient metabolic pathways for pesticide biodegradation.

Use of Biostimulants as a New Approach for the Improvement of Phytoremediation Performance—A Review

Environmental pollution is one of the most pressing global issues, and it requires priority attention. Environmental remediation techniques have been developed over the years and can be applied to polluted sites, but they can have limited effectiveness and high energy consumption and costs. Bioremediation techniques, on the other hand, represent a promising alternative. Among them, phytoremediation is attracting particular attention, a green methodology that relies on the use of plant species to remediate contaminated sites or prevent the dispersion of xenobiotics into the environment. In this review, after a brief introduction focused on pollution and phytoremediation, the use of plant biostimulants (PBs) in the improvement of the remediation effectiveness is proposed. PBs are substances widely used in agriculture to raise crop production and resistance to various types of stress. Recent studies have also documented their ability to counteract the deleterious effects of pollutants on plants, thus increasing the phytoremediation efficiency of some species. The works published to date, reviewed and discussed in the present work, reveal promising prospects in the remediation of polluted environments, especially for heavy metals, when PBs derived from humic substances, protein and amino acid hydrolysate, inorganic salts, microbes, seaweed, plant extracts, and fungi are employed.

Degrading ability and robust antioxidative defence system led to SDS tolerance in cyanobacterium Fischerella sp. lmga1

To test the tolerance and degradation potential of the cyanobacterium Fischerella sp. lmga1 for surfactant, sodium dodecyl sulfate (SDS), different doses of SDS (10, 30, 40, 50, 70 and 100 µM) were used for the growth. The lower doses of SDS supported the growth of cyanobacterium whereas the higher doses were found to be inhibitory but the cyanobacterium somehow managed its survival up to 100 µM SDS. However, a significant reduction was observed in the pigment and protein content. A substantial accumulation of carbohydrate at 70 µM SDS may act as an osmoprotectant for the survival of the cyanobacterium. The higher doses of SDS also triggered the ROS generation and lipid peroxidation which showed negative impact on the PSII efficiency. Simultaneously, an efficient ROS mitigation system (SOD and CAT activity) has also been worked up to 70 µM SDS while APX was enhanced only up to 50 µM SDS. Furthermore, the SDS degrading potential was investigated and almost 80% of the SDS was degraded after 6^th days of treatment in the cyanobacterium. Hence, the results suggested that due to robust antioxidative defence system and ability to degrade the surfactant this cyanobacterium showed significant tolerance toward SDS.

Dissipation of pyridaphenthion by cyanobacteria: Insights into cellular degradation, detoxification and metabolic regulation

Excessive use of organophosphorus pesticides such as pyridaphenthion (PY) to constrain insects induced crop loss, results in soil and water sources contamination. Cyanobacteria are sensitive biological indicators and promising tools for bioremediation of soil and water pollutants. To understand PY toxicity, detoxification and degradation in cyanobacteria, we performed a comparative study in the two diazotrophic cyanobacteria; Anabaena laxa and Nostoc muscorum. They were exposed to mild (5 mg/L) and high (10 mg/L) concentrations of PY for 7 days. Compared to A. laxa, N. muscorum efficiently showed high PY accumulation and degradation to a safe environmentally product; 6-hydroxy-2-phenylpyridazin-3(2 H)-one. PY inhibited cell growth and reduced Chl a content and photosynthesis related enzymes (PEPC and RuBisCo) activities in both species, but to less extend in N. muscorum. It also induced oxidative damage, particularly in A. laxa, as indicated by high H₂O₂, lipid peroxidation and protein oxidation levels and increased NADPH oxidase enzyme activity. N. muscorum invested more in antioxidants induction, i.e., induced ascorbate and glutathione cycle, however, these antioxidants increments in A. laxa were less pronounced. Overall, this study provides more in-deep insights into the PY toxicity and the role of N. muscorum as a promising PY remediator.

Halosulfuron methyl did not have a significant effect on diversity and community of sugarcane rhizosphere microflora

Halosulfuron methyl (HM) is a new, highly active sulfonylurea herbicide that has been widely used for weed control in agricultural production. However, its potential ecological risks remain unknown. In this study, we investigated the impact of different concentrations of HM on bacterial communities in sugarcane rhizospheric soil by using 16S rRNA gene high-throughput sequencing. The half-life of HM for 130 mg/kg, 600 mg/kg, and 1300 mg/kg spraying concentrations were 6.64, 9.19, and 9.87 d, respectively. HM application did not alter the alpha or beta diversity of the soil bacterial community, whereas some microbial populations and the main microbial functional groups were significantly altered by HM exposure. The phylum Cyanobacteria and genus unclassified Chloroflexi group KD4-96 were found to be positively correlated with HM concentration in soils, indicating that they are highly involved in the biodegradation of HM in soils. Relationship analysis between soil properties and microbial communities showed that total nitrogen and total phosphorus concentration were two key factors that significantly influenced microbial community structure. To our best knowledge, this is the first microbial ecotoxicological assessment of HM in agricultural soil.

Fabrication of Pt-Pd@ITO grown heterogeneous nanocatalyst as efficient remediator for toxic methyl parathion in aqueous media

In this study, nano-sized ITO supported Pt-Pd bimetallic catalyst was synthesized for the degradation of methyl parathion pesticide, a common extremely toxic contaminant in aqueous solution. On the characterization with different techniques, a beautiful scenario of honeycomb architecture composed of ultra-small nanoneedles or fine hairs was found. Average size of nanocatalyst also confirmed which was in the range of 3-5 nm. High percent degradation (94%) was obtained in 30 s using 1.5 × 10^- 1 mg of synthesized nanocatalyst, 0.5 mM NaBH₄, and 110 W microwave radiations power. Recyclability of nanocatalyst was efficient till 4th cycle observed during study of reusability. The supported Pt-Pd bimetallic nanocatalyst on ITO displayed many advantages over conventional methods for degradation of methyl parathion pesticide, such as high percent degradation, short reaction time, small amount of nanocatalyst, and multitime reusability. Graphical abstract Schematic illustration of reaction for degradation of methyl parathion.

Effect of light on the transformation of BDE-47 by living and autoclaved cultures of Microcystis flos-aquae and Chlorella vulgaris

Polybrominated diphenyl ethers (PBDEs) are ubiquitous and toxic contaminants found in high concentrations in watercourses, and are not well removed by conventional wastewater treatment facilities. This study aimed to evaluate the removal and transformation of BDE-47, one of the environmentally predominant PBDE congener, by a green alga (Chlorella vulgaris) and a cyanobacterium (Microcystis flos-aquae) under different light conditions. Living and autoclaved cultures were exposed to BDE-47 at a concentration of 10 μg L^-1 for 7 days. Both species removed >90% of BDE-47 very shortly after spiking. Light intensity affected the transformation of BDE-47 in living cultures of both species, since 5 to 11 times more debromination products were measured at a light intensity of 100 μmol photons m^-2 s^-1 than at 20 μmol photons m^-2 s^-1. Living cultures of M. flos-aquae transformed BDE-47 at a rate of 0.22 day^-1 while no transformation was observed in the respective autoclaved cultures. On the contrary, both living and autoclaved cultures of C. vulgaris had similar BDE-47 transformation rates of 0.05-0.06 day^-1. Debromination of BDE-47 was a predominant transformation pathway in cultures of C. vulgaris, with two times higher BDE-28 concentrations measured than in M. flos-aquae, while hydroxylation was more dominant with the cyanobacterium. Most BDE-47 and its debromination product BDE-28 were found on the cell surface of both species. These results reveal that different transformation mechanisms were involved in C. vulgaris and M. flos-aquae cultures and confirm the importance of species selection for the removal of PBDEs from contaminated environments.

Environmental behaviour of polychlorinated biphenyls in a paddy field: Impact factors and canopy effects

Paddy fields play an important role in the transport of persistent organic pollutants (POPs) due to the filter effects of canopy and their wide distribution. Thus, most studies have been focusing on the filter effects of canopy for POPs. However, shielding effects of canopy might also influence transport and portion of POPs between top and bottom. To investigate these two important processes, our study involved 30 polychlorinated biphenyls (PCBs) in a paddy field. Samples of bulk depositions, surface water, and air were taken to investigate the occurrence and the behaviour of PCBs. We found that rice canopy has potentially crucial effects on the transport of PCBs. The results showed slightly higher abundances for most of high‑chlorine PCBs (81.0%) at the top of the canopy, indicating that the high‑chlorine PCBs were intercepted by the rice leaves. Moreover, our study showed that the PCBs in surface water and soil tended to escape into air according to air, water, and soil fugacity. And we found higher atmospheric PCB levels (103 pg m^-3) at the bottom of the canopy than top (88.9 pg m^-3), indicating canopy shielding effects on escaped PCBs. In addition, the study showed that the PCBs intercepted by the rice canopy may occur in surface water and soil due to air movement and precipitation. These results suggest that paddy fields can enrich POPs, and effects of the environmental factors on POPs transport need to be investigated further.

Growth, photosynthesis and removal responses of the cyanobacteria Chroococcus sp. to malathion and malaoxon

Malathion is an organophosphorus pesticide widely used in agricultural crops, despite its toxicity. In addition, malaoxon occurs by oxidation of malathion being more toxic. The toxic effects of malathion and malaoxon in humans include hepatoxicity, breast cancer, genetic damage and endocrine disruption. The aim of this study involved assessing the effect of malathion commercial grade on Chroococcus sp., and its potential as an alternative to the removal of this pesticide and its transformation product such as malaoxon. We evaluated the effect of malathion at different concentrations (1, 25, 50, 75 and 100 ppm) on the biomass of the cyanobacteria Chroococcus sp. grown in medium BG-11; also, we analyse its ability to degrade both malathion and malaoxon into a temperature of 28 ± 2 °C and at pH 6. The results showed that 50 ppm of malathion the cyanobacteria Chroococcus sp. reached the highest removal efficiency of malathion and malaoxon (69 and 65%, respectively); also, the growth rate of Chroococcus sp. increased without inhibiting the production of chlorophyll "a", this can be explained by the hormesis phenomenon. Therefore, we consider that the cyanobacteria Chroococcus sp. may be a good candidate for bioremediation of aquatic systems contaminated with organophosphorus pesticides such as malathion and its transformation product such as malaoxon.

Effects of Interfaces of Goethite and Humic Acid-Goethite Complex on Microbial Degradation of Methyl Parathion

Microbial degradation plays an essential role in the removal of hydrophobic organic compounds (HOCs) dispersed in soil and sediment, and its performance is greatly affected by mineral particles which regulate HOCs bioavailability by interfacial adsorption. Likewise, bacteria cells attach to the surfaces of mineral particles as well but how bacterial attachment affects biodegradation is largely unknown. Here we report inhibitory effects of goethite and humic acid (HA)-goethite complex addition on microbial degradation of methyl parathion (MP). Using attenuated total reflectance-Fourier transform infrared spectroscopy, we observed that the adhesion of bacterial cells responsible for MP degradation on goethite occurred and the adhesive strength increased over time. We then replaced goethite with phosphate-adsorbed goethite to weaken the goethite-bacteria association and the inhibition of MP biodegradation was alleviated. These results suggested the formation of goethite-bacteria association hinder MP biodegradation. Meanwhile, our results showed that HA coating prevented bacterial attachment on goethite particles along with a drastically increased MP adsorption by goethite. The combined effect would lead to decreased mass fluxes of MP to bacterial cells and could represent another mechanism responsible for the decreased degradation rate observed in the current study.