Biosorption of cypermethrin from aqueous solutions by Pediococcus acidilactici: kinetics, isotherms, and mechanisms

BACKGROUND

Pediococcus acidilactici is an effective adsorbent for removing of pyrethroid insecticides. This study investigated the biosorption characteristics and mechanisms of P. acidilactici D15 using adsorption measurement, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Isotherm and kinetic models were used to analyze the biosorption process.

RESULTS

The Langmuir isotherm model best described the cypermethrin biosorption process, with the maximum adsorption capacity of P. acidilactici D15 being 21.404 mg/g. The biosorption appeared to involve monolayer coverage with uniform forces. The pseudo-second-order model also fits well. The rate-controlling steps involved intraparticle diffusion, film diffusion and chemosorption. The main cellular components involved in cypermethrin biosorption were exopolysaccharides, spheroplast, and cell wall, especially peptidoglycan. The functional groups (-OH, -NH, -CH3, -CH2, -CH, -CONH-, -CO, and -C-O-C-) from proteins, polysaccharides, and peptidoglycan on the cell surface likely played a role in binding cypermethrin. Additionally, P. acidilactici D15 effectively reduced cypermethrin in pickle wastewater.

CONCLUSION

These findings suggest that P. acidilactici D15 could be a potential agent for reducing pesticide residues, laying the groundwork for treating pickle wastewater containing such pesticide residues. © 2024 Society of Chemical Industry.

Development of Copper Nanoclusters-Based Turn-Off Nanosensor for Fluorescence Detection of Two Pyrethroid Pesticides (Cypermethrin and Lambda-Cyhalothrin)

Fluorescent copper nanoclusters (Cu NCs) were synthesized by using Withania somnifera (W. somnifera) plant extract as a biotemplate. Aqueous dispersion of W. somnifera-Cu NCs displays intense emission peak at 458 nm upon excitation at 350 nm. This fluorescence emission was utilized for the detection of two pyrethroid pesticides (cypermethrin and lambda-cyhalothrin) via "turn-off" mechanism. Upon the addition of two pyrethiod pesticides independently, the fluorescence emission of W. somnifera-Cu NCs was gradually decreased with increasing concentrations of both pesticides. It was noticed that the decrease in emission intensity at 458 nm was linearly dependent on the logarithm of both pesticides concentrations in the ranges of 0.01-100 μM and of 0.05-100 μM for cypermethrin and lambda-cyhalothrin, respectively. Consequently, the limits of detection were found to be 27.06 and 23.28 nM for cypermethrin and lambda-cyhalothrin, respectively. The as-fabricated W. somnifera-Cu NCs acted as a facile sensor for the analyses of cypermethrin and lambda-cyhalothrin in vegetables (tomato and bottle gourd), which demonstrates that it could be used as portable sensing platform for assaying of two pyrethroid pesticides in food samples.

Cypermethrin adsorption by Lactiplantibacillus plantarum and its behavior in a simulated fecal fermentation model

The presence of cypermethrin in the environment and food poses a significant threat to human health. Lactic acid bacteria have shown promise as effective absorbents for xenobiotics and well behaved in wide range of applications. This study aimed to characterize the biosorption behavior of cypermethrin by Lactiplantibacillus plantarum RS60, focusing on cellular components, functional groups, kinetics, and isotherms. Results indicated that RS60 exopolysaccharides played a crucial role removing cypermethrin, with the cell wall and protoplast contributing 71.50% and 30.29% to the overall removal, respectively. Notably, peptidoglycans exhibited a high affinity for cypermethrin binding. The presence of various cellular surface groups including -OH, -NH, -CH3, -CH2, -CH, -P = O, and -CO was responsible for the efficient removal of pollutants. Additionally, the biosorption process demonstrated a good fit with pseudo-second-order and Langmuir-Freundlich isotherm. The biosorption of cypermethrin by L. plantarum RS60 involved complex chemical and physical interactions, as well as intraparticle diffusion and film diffusion. RS60 also effectively reduced cypermethrin residues in a fecal fermentation model, highlighting its potential in mitigating cypermethrin exposure in humans and animals. These findings provided valuable insights into the mechanisms underlying cypermethrin biosorption by lactic acid bacteria and supported the advancement of their application in environmental and health-related contexts. KEY POINTS: • Cypermethrin adsorption by L. plantarum was clarified. • Cell wall and protoplast showed cypermethrin binding ability. • L. plantarum can reduce cypermethrin in a fecal fermentation model.

A novel cold-adapted pyrethroid-degrading esterase from Bacillus subtilis J6 and its application for pyrethroid-residual alleviation in food matrix

Prolonged and widespread use of pyrethroid pesticides a significant concern for human health. The initial step in pyrethroid bioremediation involves the hydrolysis of ester-bond. In the present study, the esterase genes est10 and est13, derived from Bacillus subtilis, were successfully cloned and expressed in Escherichia coli. Recombinant Est10 and Est13 were classified within esterase families VII and XIII, respectively, both of which exhibited conserved G-X-G-X-G motifs. These enzymes demonstrated the capability to degrade pyrethroids, with Est13 exhibiting superior efficiency, and thus was selected for further investigation. The degradation products of β-cypermethrin by Est13 were identified as 3-phenoxybenzoic acid, 3-phenoxybenzaldehyde, and 3-(2,2-Dichloroethenyl)- 2,2-dimethyl-cyclopropanecarboxylate, with key catalytic triads comprising Ser93, Asp192, and His222. Notably, Est13 exhibited the highest β-cypermethrin-hydrolytic activity at 25 °C and a pH of 7.0, showing robust stability in low and medium temperature environment and a broad range of pH levels. Furthermore, Est13 displayed notable resistance to organic solvents and NaCl, coupled with wide substrate specificity. Moreover, Est13 exhibited substantial efficiency in removing β-cypermethrin residues from various food items such as milk, meat, vegetables, and fruits. These findings underscore the potential of Est13 for application in the bioremediation of pyrethroid-contaminated environments and reduction of pyrethroid residues in food products.

Transcriptomic analysis reveals peripheral pathway in 3-phenoxybenzoic acid degradation by Aspergillus oryzae M-4

As a major intermediate metabolite of synthetic pyrethroids, the occurrence of 3-phenoxybenzoic acid hinders the decomposition of the parent pesticide and poses uncertain risks to environmental ecology and living organisms. Strain Aspergillus oryzae M-4 was previously reported to degrade 3-PBA and several substances were identified as downstream transformation products (TPs). But the mechanism underlying the cleavage of ether bond remains largely unclear. Here, we attempted to address such concern through identifying the peripheral TPs and analyzing transcriptomics, coupled with serial batch degradation experiments. Analysis results of chromatographic/mass spectrometry suggested that 3-PBA underwent twice hydroxylation, to yield mono- and dihydroxylated 3-PBA successively. In parallel, a mutual transformation between 3-PBA and 3-phenoxybenzyl alcohol (3-PBOH) also existed. The proposal of peripheral pathway represents an important advance towards fully understanding the whole 3-PBA metabolism in M-4. A specific altered metabolization was found for the first time, that is, resting cells of M-4 skipped the reduction step and initiate hydroxylation directly, by comparison with growing cells. Transcriptome analysis indicated that 3-PBA induced the up-regulation of genes related to energy investment, oxidative stress response, membrane transport and DNA repair. In-depth functional interpretation of differential expression genes suggested that the generation 3-PBOH and hydroxylated 3-PBA may be due to the participation of flavin-dependent monooxygenases (FMOs) and cytochrome P450 (CYP450), respectively. This study provides new insight to reveal the biodegradation mechanism of 3-PBA by A. oryzae M-4.

Optimization and adsorption characteristics of beads based on heat-inactivated bacterial biomaterial towards the pesticide Cypermethrin

AIMS

Beads containing heat-inactivated bacterial biomaterial (BBBs) were prepared for removal of cypermethrin (CPM) and the conditions for this removal were evaluated and optimized via single-factor coupled orthogonal experiments based on five factors. The adsorption characteristics of BBBs and the binding mechanism were then explored.

METHODS AND RESULTS

Results showed that the adsorption rate of CPM could reach 98% with beads prepared under optimized conditions: equal volumes of Lactobacillus cell debris derived from 1×1011 CFU; 2% hydroxypropyl-β-cyclodextrin and 2.5% activated carbon concentration, were mixed to give mixture TM, and this and SA, was mixed 1:4 with sodium alginate (SA) and beads were prepared using a 26-Gauge needle). The best adsorption conditions were initial CPM concentration of 10 mg l-1, incubation time of 24 h, and rotational speed of 180 rpm. BBBs have a well-formed structure and abundant surface functional groups, such as -COOH, -OH, -NH, -CH, -CO, -C=C. The adsorption process conformed to pseudo-second-order kinetic, and it was also a Freundlich monolayer adsorption, and the calculated maximum adsorption capacity was 9.69 mg g-1 under optimized conditions.

CONCLUSIONS

BBBs showed the highest CPM removal capacity and a good tolerance ability.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our results provided a theoretical foundation for developing an adsorbent with heat-inactivated Lactobacillus plantarum (L. plantarum) RS60 for removing CPM in wastewater or drinks.

Role of Plasmid in Pesticide Degradation and Metal Tolerance in Two Plant Growth-Promoting Rhizobacteria Bacillus cereus (NCIM 5557) and Bacillus safensis (NCIM 5558)

Disha A (Bacillus cereus) and Disha B (Bacillus safensis) were isolated from pesticide-infested agricultural field and showed tolerance against pesticides, heavy metals, and antibiotics. The isolates exhibited PGPR activities in vitro as well as in field conditions in lentil (Lens culinaris) and cow pea (Vigna unguiculata). Both the Bacillus species could not be grown in mineral salt medium but efficiently grown in the media supplemented with pesticide (imidacloprid/carbendazim) demonstrating the utilization of pesticide as carbon/nitrogen source. The HPLC studies exhibited the pesticide (imidacloprid/carbendazim) degradation by both the bacteria. B. safensis showed better degradation of carbendazim (88.93%) and imidacloprid (82.48%) than that of B. cereus 78.07% and 49.12%, respectively. The bacterial isolates showed high concentration of heavy metal tolerance viz. lead, molybdenum, cadmium, copper, cobalt, and zinc, except mercury. Both the bacteria possessed single plasmid. The plasmid-cured isolates of B. cereus did not tolerate any pesticide, whereas that of B. safensis tolerated all the pesticides, like wild strains. The plasmid curing experiments did not affect the heavy metal tolerance ability of both the bacteria indicating the genomic nature of heavy metal tolerance genes, whereas pesticide resistance genes are plasmid-dependent in B. cereus but genomic in B. safensis.

Characterization, mechanism of cypermethrin biosorption by Saccharomyces cerevisiae strains YS81 and HP and removal of cypermethrin from apple and cucumber juices by inactive cells

Cypermethrin is a common food contaminant and environmental pollutant that cause health threats to animals and humans. In this study, the characterization, mechanism, and application of cypermethrin removal by Saccharomyces cerevisiae were investigated. The binding of cypermethrin by the strains S. cerevisiae YS81 and HP was rapid and reached equilibrium at 2-8 h. The removal efficiency was dependent on incubation temperature and yeast concentration, whereas cypermethrin binding was not affected by pH. Heat and acid treatments enhanced the binding ability. Both strains survived in simulated digestion juices and removed cypermethrin effectively under simulated gastrointestinal conditions. Among the strains tested, the YS81 strain was the better candidate for cypermethrin concentration reduction. For the two S. cerevisiae strains, the biosorption kinetics and isotherm followed the pseudo-second-order model and Langmuir model well. The cell walls and the protoplasts were the main yeast cell components involved in cypermethrin binding. Fourier transformed infrared spectroscopy analysis revealed that -OH, -NH, -C-N, -COO^-, and -C-O played a major role in binding cypermethrin. Inactive cells effectively removed cypermethrin from apple and cucumber juices and did not affect the physico-chemical properties. Therefore, S. cerevisiae strains YS81 and HP may be used for cypermethrin reduction in food or feed.

Purification and characterization of a novel cypermethrin-hydrolyzing esterase from Bacillus licheniformis B-1

Cypermethrin (CY) is a synthetic pyrethroid widely used to control insect pests and it elicits a toxic effect on the human body. In this study, Bacillus licheniformis B-1 isolated from tea garden soil was used to degrade CY effectively. A specific enzyme was mainly localized in the extracellular compartments of B-1. This enzyme was identified as an esterase that could be produced without CY. The enzyme was purified 23.03-fold to apparent homogeneity with 8.38% overall recovery by ammonium sulfate precipitation, anion exchange chromatography, and gel filtration chromatography. The molecular mass of the CY-degrading enzyme was 66.4 kDa, and its optimal pH and temperature were 8.5 and 40 °C, respectively. Appropriate Zn²⁺ , Mn²⁺ , Mg²⁺ , Tween 80, SDS, Triton X-100, and BSA concentrations could greatly increase the activity of this enzyme. By contrast, EDTA, 1,10-phenanthroline, NaF, and PMSF strongly inhibited its activity. The purified enzyme showed K_m and V_max values were 5.532 nmol/mL and 33.445 nmol/min. The CY residue in lettuce and cherry tomatoes could be removed more than 50% under the conditions of the treatment concentration for 500 mg/L and the enzyme preparation dilution of 100 times. These results suggested that the CY-degrading enzyme, a constitutive enzyme that mainly exists in the extracellular space, was a novel esterase that might be used to detoxify CY, and could remove CY in vegetables effectively. PRACTICAL APPLICATION: Our research found a novel cypermethrin-hydrolyzing esterase from Bacillus licheniformis B-1 and proved that the enzyme could remove cypermethrin in vegetables effectively.

Screening of lactic acid bacteria for their capacity to bind cypermethrin in vitro and the binding characteristics and its application

In this study, the cypermethrin binding characteristics of lactic acid bacteria were investigated for the first time. Two strains, Lactobacillus plantarum RS60 and Pediococcus acidilactici D15, possessed the highest cypermethrin removal capacity and good tolerance to simulated digestive juices. They were employed for further studies on cypermethrin binding characteristics. 55.06% and 56.46% of cypermethrin were removed within 0.25 h by strains RS60 and D15, respectively. The effect of pH on binding capacity was negligible. Heat treatment enhanced cypermethrin binding rate. Moreover, inactive cells were capable of removing cypermethrin from fruit and vegetable juices, with over 60% cypermethrin reduction within 2 h. No adverse effect was found on the quality of juice during the biosorption process. Besides, these two strains also could bind other several pyrethroids and 3-phenoxybenzoic acid. These findings indicated that L. plantarum RS60 and P. acidilactici D15 may be useful to reduce cypermethrin in contaminated foods.

Substrate regulation on co-metabolic degradation of β-cypermethrin by Bacillus licheniformis B-1

Beta-cypermethrin (β-CY) residues are a serious threat to food safety and human health. However, the residues are not efficiently biodegraded because microorganisms preferentially use the nutrients found in food and the environment for growth. In this study, the mechanisms underlying nutrient regulation during co-metabolic degradation of β-CY by Bacillus licheniformis B-1 were investigated. The strain B-1 resting cells and the suspension containing NaN₃ showed no significant differences in β-CY degradation. The co-metabolic degradation and strain B-1 growth could be separately inhibited by iodoacetic acid and sodium fluoride. Adenosine monophosphate (AMP), fructose 1-6 bisphosphate (F1-6BP), Mg²⁺, and Mn²⁺ could improve the degradation, whereas adenosine triphosphate (ATP), alanine (Ala), phenylalanine (Phe), and phosphoenolpyruvate (PEP) were found to exert the opposite effect, indicating that β-CY degradation was positively associated with pyruvate kinase activity. Furthermore, glycerol, urea, ammonium chloride and peptone improved β-CY degradation in corn flour. The results provided a promising approach for nutrient regulation of pyrethroids biodegradation in food and the environment.

Simultaneous degradation of β-cypermethrin and 3-phenoxybenzoic acid by Eurotium cristatum ET1, a novel "golden flower fungus" strain isolated from Fu Brick Tea

Beta-cypermethrin (β-CY) and its major metabolite 3-phenoxybenzoic acid (3-PBA) spread extensively in the environment because of utilization in agricultural and home formulations, exerting negative impact on environment as well as human health. Several golden flower fungi were isolated from fu brick tea, by which the biodegradation of β-CY and 3-PBA was evaluated, turning out strain Eurotium cristatum ET1 had the highest capacity. Furthermore, β-CY and 3-PBA degradation rates were positively correlated with biomass of E. cristatum ET1, and the processes of degradation fitted well with a first-order kinetic equation. The half-lives of β-CY and 3-PBA ranged from 3.382 to 11.517 days and 1.749 to 3.194 days, respectively, under different substrate concentrations, incubation temperatures, and pH values. The degraded products were analyzed using gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry, and results showed that E. cristatum ET1 degrades β-CY by transforming it into 3-PBA, which is then gradually metabolized into phenol and catechol. Moreover, E. cristatum ET1 showed efficiency in degrading these metabolites. Our results suggest that this strain is a potential microorganism for bioremediation of pesticide-contaminated environments and fermented foods.

Co-Metabolic Degradation of β-Cypermethrin and 3-Phenoxybenzoic Acid by Co-Culture of Bacillus licheniformis B-1 and Aspergillus oryzae M-4

The degradation efficiency of organic contaminants and their associated metabolites by co-culture of microbes is mainly limited by toxic intermediates from co-metabolic degradation. In this study, we investigated the degradation of β-cypermethrin (β-CY) and 3-phenoxybenzoic acid (3-PBA) by co-culture of Bacillus licheniformis B-1 and Aspergillus oryzae M-4, as well as the influences of β-CY and 3-PBA metabolites on their degradation and the growth of strains B-1 and M-4. Our results indicated that 100 mg/L β-CY was degraded by 78.85%, and 3-PBA concentration was 0.05 mg/L after 72 h. Compared with using only strain B-1, the half-life (t1/2) of β-CY by using the two strains together was shortened from 84.53 h to 38.54 h, and the yield coefficient of 3-PBA was decreased from 0.846 to 0.001. At 100 mg/L of 3-PBA and gallic acid, β-CY and 3-PBA degradation were only 17.68% and 40.45%, respectively. As the toxic intermediate derived from co-metabolic degradation of β-CY by strain B-1, 3-PBA was efficiently degraded by strain M-4, and gallic acid, as the toxic intermediate from co-metabolic degradation of 3-PBA by strain M-4, was efficiently degraded by strain B-1. These results provided a promising approach for efficient biodegradation of β-CY and 3-PBA.

Simultaneous Determination of β-Cypermethrin and Its Metabolite 3-Phenoxybenzoic Acid in Microbial Degradation Systems by HPLC-UV

The wide use of pesticides in agriculture is necessary to guarantee adequate food production worldwide. However, pesticide residues have caused global concern because of their potential health risk to consumers. In this study, we could identify β-cypermethrin (β-CY) and its degradation product 3-phenoxybenzoic acid (3-PBA) by liquid chromatograph-mass spectrometry. Few studies on the simultaneous determination of β-CY and its metabolites have been carried out so far; hence, we established a high-performance liquid chromatography method to determine the concentrations of both β-CY and 3-PBA simultaneously in microbial degradation systems. In this study, a novel β-CY degrading strain, Bacillus licheniformis B-1, was isolated from a tea garden soil, utilizing β-CY as a growth substrate. Good linear relationships between β-CY and 3-PBA were observed and the concentrations of reference solutions were between 0.50 and 60.00 µg/mL. Satisfactory stability and intra- and interday precision were obtained. The limits of detection were 0.06 and 0.13 µg/mL for β-CY and 3-PBA, respectively, and the corresponding limits of quantification were 0.21 and 0.34 µg/mL, respectively. Spiking recoveries for β-CY varied from 98.38 to 105.80%, with relative standard deviations (RSDs) varying from 1.49 to 3.93%. Spiking recoveries for 3-PBA varied from 99.59 to 101.20%, with RSDs varying from 0.58 to 3.64%. The proposed method has advantages of simplicity, rapidity, high accuracy, good separation and reproducibility; thus, it is ideally suitable for simultaneous determination of β-CY and 3-PBA in microbial degradation systems.

Effects of Two Surfactants and Beta-Cyclodextrin on Beta-Cypermethrin Degradation by Bacillus licheniformis B-1

The biodegradation efficiency of beta-cypermethrin (β-CY) is low especially at high concentrations mainly due to poor contact between this hydrophobic pesticide and microbial cells. In this study, the effects of two biodegradable surfactants (Tween-80 and Brij-35) and β-cyclodextrin (β-CD) on the growth and cell surface hydrophobicity (CSH) of Bacillus licheniformis B-1 were studied. Furthermore, their effects on the solubility, biosorption, and degradation of β-CY were investigated. The results showed that Tween-80 could slightly promote the growth of the strain while Brij-35 and β-CD exhibited little effect on its growth. The CSH of strain B-1 and the solubility of β-CY were obviously changed by using Tween-80 and Brij-35. The surfactants and β-CD could enhance β-CY biosorption and degradation by the strain, and the highest degradation was obtained in the presence of Brij-35. When the surfactant or β-CD concentration was 2.4 g/L, the degradation rate of β-CY in Brij-35, Tween-80, and β-CD treatments was 89.4%, 50.5%, and 48.1%, respectively. The half-life of β-CY by using Brij-35 was shortened by 69.1 h. Beta-CY content in the soil with both strain B-1 and Brij-35 decreased from 22.29 mg/kg to 4.41 mg/kg after incubation for 22 d. This work can provide a promising approach for the efficient degradation of pyrethroid pesticides by microorganisms.

Characterization of a novel β-cypermethrin-degrading Aspergillus niger YAT strain and the biochemical degradation pathway of β-cypermethrin

Aspergillus niger YAT strain was obtained from Chinese brick tea (Collection number: CGMCC 10,568) and identified on the basis of morphological characteristics and internal transcribed spacer (ITS) sequence. The strain could degrade 54.83 % of β-cypermethrin (β-CY; 50 mg L(-1)) in 7 days and 100 % of 3-phenoxybenzoic acid (3-PBA; 100 mg L(-1)) in 22 h. The half-lives of β-CY and 3-PBA range from 3.573 to 11.748 days and from 5.635 to 12.160 h, respectively. The degradation of β-CY and 3-PBA was further described using first-order kinetic models. The pathway and mechanism of β-CY degraded by YAT were investigated by analyzing the degraded metabolites through high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). Relevant enzymatic activities and substrate utilization were also investigated. β-CY degradation products were analyzed. Results indicated that YAT strain transformed β-CY into 3-PBA. 3-PBA was then gradually transformed into permethric acid, protocatechuic acid, 3-hydroxy-5-phenoxy benzoic acid, gallic acid, and phenol gradually. The YAT strain can also effectively degrade these metabolites. The results indicated that YAT strain has potential applications in bioremediation of pyrethroid insecticide (PI)-contaminated environments and fermented food.

Simultaneous degradation of cypermethrin and its metabolite, 3-phenoxybenzoic acid, by the cooperation of Bacillus licheniformis B-1 and sphingomonas sp. SC-1

Cypermethrin (CY) and its metabolite, 3-phenoxybenzoic acid (3-PBA), generally coexist in agricultural soil and cause a toxic effect on the human body. In this study, CY and its metabolite 3-PBA were simultaneously degraded by the cooperation of Bacillus licheniformis B-1 and Sphingomonas sp. SC-1. The effects of the inoculation proportion and inoculation method of these two strains, cultivation time, and initial CY content on the degradation of CY and 3-PBA were investigated. Furthermore, the degradation of CY and 3-PBA in soil environment by using the cooperation of these two strains was also determined. When the inoculation proportion of the biomass of strain B-1/strain SC-1 was 3.3:6.7, strain B-1 was inoculated first, and strain SC-1 was inoculated after 24 h of cultivation, 75.60% CY (100 mg L(-1)) was degraded at 72 h and the 3-PBA content was 10.31 mg L(-1). Compared with those by using only strain B-1, the half-life of CY by using these two strains was shortened from 71.90 to 35.71 h, and the yield coefficient of 3-PBA was decreased from 0.8938 to 0.2651. As in the soil environment, the CY content by using these two strains within a period of 25 days declined from 22.71 to 5.33 mg kg(-1) and the 3-PBA content was 1.84 mg kg(-1). Compared with those by using only strain B-1, the half-life of CY by using these two strains was shortened from 19.86 to 11.34 days and the yield coefficient of 3-PBA was decreased from 0.5302 to 0.2056. This work could develop a promising approach for the simultaneous degradation of CY and its metabolite 3-PBA in agricultural soil.