Degradation of pendimethalin by the yeast YC2 and determination of its two main metabolites

Bacterial community structure analysis of sludge from Taozi lake and isolation of an efficient 17β-Estradiol (E2) degrading strain Sphingobacterium sp. GEMB-CSS-01

Environmental challenges arising from organic pollutants pose a significant problem for modern societies. Efficient microbial resources for the degradation of these pollutants are highly valuable. In this study, the bacterial community structure of sludge samples from Taozi Lake (polluted by urban sewage) was studied using 16S rRNA sequencing. The bacterial phyla Proteobacteria, Bacteroidetes, and Chloroflexi, which are potentially important in organic matter degradation by previous studies, were identified as the predominant phyla in our samples, with relative abundances of 48.5%, 8.3%, and 6.6%, respectively. Additionally, the FAPROTAX and co-occurrence network analysis suggested that the core microbial populations in the samples may be closely associated with organic matter metabolism. Subsequently, sludge samples from Taozi Lake were subjected to enrichment cultivation to isolate organic pollutant-degrading microorganisms. The strain Sphingobacterium sp. GEMB-CSS-01, tolerant to sulfanilamide, was successfully isolated. Subsequent investigations demonstrated that Sphingobacterium sp. GEMB-CSS-01 efficiently degraded the endocrine-disrupting compound 17β-Estradiol (E2). It achieved degradation efficiencies of 80.0% and 53.5% for E2 concentrations of 10 mg/L and 20 mg/L, respectively, within 10 days. Notably, despite a reduction in degradation efficiency, Sphingobacterium sp. GEMB-CSS-01 retained its ability to degrade E2 even in the presence of sulfanilamide concentrations ranging from 50 to 200 mg/L. The findings of this research identify potential microbial resources for environmental bioremediation, and concurrently provide valuable information about the microbial community structure and patterns within Taozi Lake.

High-throughput method for screening pendimethalin-degrading bacteria from one microbial bank

The extensive use of chemical pesticides, such as herbicides, has resulted in significant environmental pollution. Microbial degradation represents a crucial approach for managing this pesticide-associated pollution, with enrichment culturing serving as a method for isolating pesticide-degrading microorganisms. However, the efficiency of this strategy is limited, often yielding only a few isolated strains. In this study, a new mineral salt medium (MSM) was developed, and a high-throughput method was used for screening pendimethalin-degrading bacteria by measuring the bacterial growth in the MSM. The utilization of this method resulted in the isolation of 56 pendimethalin-degrading bacteria from approximately 2000 bacterial strains, including 37 Bacillus spp., 10 Alcaligenes spp., 5 Pseudomonas spp., and other 4 strains identified for the first time as pendimethalin-degrading strains. This method may hold promise not only for isolating bacterial strains capable of degrading other pesticides but also for facilitating the utilization of the substantial bacterial strains stored in bacterial banks.

Unraveling the contemporary use of microbial fuel cell in pesticide degradation and simultaneous electricity generation: a review

Pesticide is an inevitable substance used worldwide to kill pests, but their indiscriminate use has posed serious complications to health and the environment. Various physical, chemical, and biological methods are employed for pesticide treatment, but this paper deals with microbial fuel cell (MFC) as a futuristic technology for pesticide degradation with electricity production. In MFC, organic compounds are utilized as the carbon source for electricity production and the generation of electrons which can be replaced with pollutants such as dyes, antibiotics, and pesticides as carbon sources. However, MFC is been widely studied for a decade for electricity production, but its implementation in pesticide degradation is less known. We fill this void by depicting a real picture of the global pesticide scenario with an eagle eye view of the bioremediation techniques implemented for pesticide treatment with phytoremediation and rhizoremediation as effective techniques for efficient pesticide removal. The enormous literature survey has revealed that not many researchers have ventured into this new arena of MFC employed for pesticide degradation. Based on the Scopus database, an increase in annual trend from 2014 to 2023 is observed for MFC-implemented pesticide remediation. However, a novel MFC to date for effective remediation of pesticides with simultaneous electricity generation is discussed for the first time. Furthermore, the limitation of MFC technology and the implementation of MFC and rhizoremediation as a clubbed system which is the least applied can be seen as promising and futuristic approaches to enhance pesticide degradation by bacteria and electricity as a by-product.

Bioremediation of a trifluralin contaminated soil using bioaugmentation with novel isolated bacterial strains and cyclodextrin

Trifluralin (TFL) is a highly persistent with a strong adsorption capacity on soil particles herbicide. This study was to isolate microbial consortia and bacterial strains from a soil with a historical application of pesticides to evaluate their potential to degrade TFL in soil. Different bioremediation techniques were considered for increasing the effectiveness of TFL degradation in soil. These techniques consisted of: i) biostimulation, using a nutrients solution (NS); ii) bioaugmentation, using a natural microbial consortium (NMC), seven individual bacterial strains isolated from NMC, and an artificial bacterial consortium formed by the seven TFL-degrading bacterial strains (ABC); iii) bioavailability enhancement, using a biodegradable compound, a randomly methylated cyclodextrin, RAMEB. Biostimulation using NS leads up to 34 % of soil TFL biodegraded after 100 d. When the contaminated soil was inoculated with NMC or ABC consortia, TFL loss increased up to 62 % and 74 %, respectively, with DT₅₀ values (required time for the pollutant concentration to decline to half of its initial value) of 5.9 and 11 d. In the case of soil inoculation with the isolated individual bacterial strains, the extent of TFL biodegradation ranged widely from 2.3 % to 55 %. The most efficient bacterial strain was Arthrobacter aurescens CTFL7 which had not been previously described in the literature as a TFL-degrading bacterium. Bioaugmentation with CTFL7 bacterium was also tested in the presence of RAMEB, provoking a drastic increase in herbicide biodegradation up to 88 %, achieving a DT₅₀ of only 19 d. Cyclodextrins had never been tested before for enhancement of TFL biodegradation. An ecotoxicity assay was performed to confirm that the proposed bioremediation techniques were also capable to reduce toxicity. A Microtox® test showed that after application A. aurescens CTF7 and A. aurescens CTF7 + RAMEB, the TFL-contaminated soil, which initially presented acute toxicity, became non-toxic at the end of the biodegradation experiments.

The effects of the "Stomp" herbicide application on the microbial prevalence in the soil

Agricultural production has benefited a lot from herbicides; however, the use of herbicides caused many environmental problems. Herbicide application can affect the biodiversity of an ecosystem by killing non-target organisms. Microorganisms in the soil are important factors for plant growth; they represent the biological factor of soil fertility. Herbicides can have a beneficial effect on the development of some microorganisms and a negative on others, leading to depletion of microbial diversity in soil. The objective of this work is to determine microbial activity in the soil and to isolate herbicide-resistant bacteria after the use of the "Stomp" herbicide. Agar plate method was used for the determination of microbial prevalence in the soil. The results showed an increase in the total number of bacteria, ammonifiers, fungi, and actinomycetes. Nine isolates, mostly Gram-positive spore-forming rods, showed an ability to grow in the mineral salt medium with different concentrations of "Stomp" herbicide. Isolates G1/1 and G1/2, showed high level of tolerance at the initial pendimethalin concentration of 25 mg/l. Those isolates have the potential to be used to decontaminate herbicide affected ecosystems.

Degradation studies of pendimethalin by indigenous soil bacterium Pseudomonas strain PD1 using spectrophotometric scanning and FTIR

In this study pendimethalin degrading indigenous soil bacterium was isolated from rice field (supplemented with pendimethalin) and identified as, Pseudomonas strain PD1 on the basis of 16S rRNA phylogenetic analysis. Biodegradation of pendimethalin by this strain was evaluated by spectrophotometric scanning and FTIR analysis of degraded compounds in minimal salt media. Decrease in concentration of pendimethalin at λ_max (430 nm) under spectrophotometric scanning is a measurement of time taken by bacterium strain PD1 to degrade pendimethalin. Degraded products were further analyzed by comparing stretching and bending pattern of chemical groups attached to compounds using FTIR spectroscopy. FTIR profile represented disappearance of nitrate group in degraded product by bacterium strain PD1 in minimal salt medium. Molecular docking of pendimethalin on nitro-reductase was done to suggest first enzyme of pathway used by bacterium strain PD1 to degrade pendimethalin. Analysis on degradation by strain PD1 shows that newly isolated strain PD1 can degrade 77.05% of pendimethalin at 50 mgL^-1 concentration in 30 h incubation under room temperature. Thus, the study here shed a light on degradation potential of Pseudomonas.

Culturable Yeasts as Biofertilizers and Biopesticides for a Sustainable Agriculture: A Comprehensive Review

The extensive use of synthetic fertilizers and pesticides has negative consequences in terms of soil microbial biodiversity and environmental contamination. Faced with this growing concern, a proposed alternative agricultural method is the use of microorganisms as biofertilizers. Many works have been focused on bacteria, but the limited literature on yeasts and their potential ability to safely promote plant growth is gaining particular attention in recent years. Thus, the objective of this review is to highlight the application of yeasts as biological agents in different sectors of sustainable agricultural practices through direct or indirect mechanisms of action. Direct mechanisms include the ability of yeasts to provide soluble nutrients to plants, produce organic acids and phytohormones (indole-3-acetic acid). Indirect mechanisms involve the ability for yeasts to act as biocontrol agents through their high antifungal activity and lower insecticidal and herbicidal activity, and as soil bioremediating agents. They also act as protective agents against extreme environmental factors by activating defense mechanisms. It is evident that all the aspects that yeasts offer could be useful in the creation of quality biofertilizers and biopesticides. Hence, extensive research on yeasts could be promising and potentially provide an environmentally friendly solution to the increased crop production that will be required with a growing population.

Dissipation kinetics and biological degradation by yeast and dietary risk assessment of fluxapyroxad in apples

The aim of this study was to investigate the dissipation kinetics of fluxapyroxad in apples, the influence of biological treatment with yeast, and the estimation of dietary exposure for consumers, both adults and children. The gas chromatography technique with the electron capture detector was used to analyse the fluxapyroxad residues. Samples of apples were prepared by the quick, easy, cheap, effective, rugged and safe (QuEChERS) method. The average fluxapyroxad recoveries in apple samples ranged from 107.9 to 118.4%, the relative standard deviations ranged from 4.2 to 4.7%, and the limit of quantification was 0.005 mg/kg. The dissipation half-lives in Gala and Idared varieties were 8.9 and 9.0 days, respectively. Degradation levels of the tested active substance after application of yeast included in a biological preparation Myco-Sin were 59.9% for Gala and 43.8% for Idared. The estimated dietary risk for fluxapyroxad in apples was on the acceptable safety level (below 9.8% for children and 1.9% for adults) and does not pose a danger to the health of consumers.

Yeast a potential bio-agent: future for plant growth and postharvest disease management for sustainable agriculture

The native microbial flora and fauna are replaced by commercial chemical fertilizers and pesticides, in the current agricultural system. Imbalance of beneficial microbial diversity and natural competitors increases the severity of plant diseases. Hence, sustainable agricultural practices like bio-inoculant, stress tolerant consortium, crop rotation and mix cropping sequences is only the solution of recharging the microbial population in soils to make healthier for crop productivity and suppression of soil borne phytopathogen. Microorganisms use several direct mechanism activities, e.g. production of plant hormones (indole-3-acetic acid), ammonium, siderophore and nutrient solubilization, and indirect mechanism activities, e.g. hydrogen cyanide, chitinase, protease and antibiotic for plant growth promotion. The plant growth-promoting effect of bacteria, fungi, mycorrhizal fungi and algae is widely explored. Yeast is a single-celled microbe classified as members of the kingdom fungi. Yeast and their product use in the food industry, medical science and biotechnological research purpose but very few literatures reported that yeasts have the ability to produce a group of plant growth-promoting activities and biocontrolling activity. Therefore, the main aim of this mini review is to highlight the application of yeasts as biological agents in different sectors of sustainable farming practices.

Identification of a Novel Nitroreductase LNR and Its Role in Pendimethalin Catabolism in Bacillus subtilis Y3

Microbial degradation plays a major role in the dissipation of pendimethalin, and nitroreduction is an initial and detoxicating step. Previously, a pendimethalin nitroreductase, PNR, was identified in Bacillus subtilis Y3. Here, another pendimethalin nitroreductase from strain Y3, LNR, was identified. LNR shares only 40% identity with PNR and reduces the aromatic ring C-6 nitro group of pendimethalin and both nitro groups of trifluralin, butralin, and oryzalin. The catalytic activities against the four dinitroanilines were much higher for LNR than for PNR. lnr deletion significantly reduced the pendimethalin-reduction activity (60% activity loss), while pnr deletion led to only 30% activity loss, indicating that both LNR and PNR were involved in pendimethalin nitroreduction in strain Y3; however, LNR played the major role. This study facilitates the elucidation of pendimethalin catabolism and provides degrading enzyme resources for the removal of dinitroaniline herbicide residues in environment and agricultural products.