Anise essential oil immobilized in chitosan microparticles: a novel bactericidal material for food protection.

Foodborne infections in humans are one of the major concerns of the food industries, especially for minimally processed foods (MPF). Thereby, the packaging industry applies free chlorine in the sanitization process, ensuring the elimination of any fecal coliforms or pathogenic microorganisms. However, free chlorine's propensity to react with organic matter, forming toxic compounds such as trihalomethanes and haloacetic acid. Therefore, the present work aimed to synthesize a novel organic biomaterial as an alternative to free chlorine. Chitosan microparticles were produced, with Pimpinella anisum (anise) essential oil immobilized in the biopolymer matrix (MPsQTO). The characterization of this biomaterial was done through GC-MS/MS, FT-IR, and SEM. Antimicrobial assays proved that the MPsQTO presented antibacterial activity for Escherichia coli, Salmonella typhi, Pseudomonas aeruginosa, and Bacillus subtilis at 300 µL mL-1 of concentration. The fluorescence microscope also showed the MPsQTO targets the cytoplasmatic membrane, which is responsible for cell death in the first minutes of contact. Studies with the mutant B. subtilis (amy::pspac-ftsZ-gfpmut1) and the Saccharomyces cerevisiae D7 also proved that the biomaterial did not affect the genetic material and did not have any mutagenic/carcinogenic effect on the cells. The sanitization assays with pumpkin MPF proved that the MPsQTO is more effective than free chlorine, increasing the shelf-life of the MPF. Consequently, the novel biomaterial proposed in this work is a promising alternative to traditional chemical sanitizers.

Neem Essential Oil as an Antifungal Agent against Phyllosticta citricarpa.

The fungus Phyllosticta citricarpa is a quarantine phytopathogen responsible for causing citrus black spot (CBS) disease. To export fruits to CBS-free countries, they must undergo a sanitation process to ensure disease control. In this study, neem essential oil (NEO) was tested against P. citricarpa for the first time as an alternative sanitizer. In vitro experiments were conducted to determine the inhibition concentration of NEO for P. citricarpa, and the mode of action of the essential oil was evaluated. In vivo assays were performed to simulate the sanitization process used in packinghouses. NEO was characterized by GC-MS/MS. The results revealed that NEO at 100 µL·mL-1 exhibited a similar inhibitory effect as copper oxychloride, suppressing 89.68 ± 1.14% of fungal mycelium growth. Fluorescence microscopy experiments demonstrated that NEO functions by disrupting the cytoplasmic membrane of fungal hyphae, leading to their death within 30 minutes of contact with NEO. GC-MS/MS characterization revealed a high presence of phenolic compounds, which serve as the primary antifungal agents responsible for the action against fungal hyphae. In vivo assays showed that NEO at 100 µL·mL-1 also reduced microorganisms (CFU mL-1) by 93.00 ± 3.88% compared to the negative control. Overall, the results demonstrate that NEO can effectively serve as an alternative sanitizer against P. citricarpa in citrus packinghouses. Our findings allow future studies to explore the use of NEO for sanitizing other fruits and combating different phytopathogens to broaden its potential application in fruit sanitation for export.

Antibacterial action and target mechanisms of zinc oxide nanoparticles against bacterial pathogens.

Zinc oxide nanoparticles (ZnO NPs) are one of the most widely used nanoparticulate materials due to their antimicrobial properties, but their main mechanism of action (MOA) has not been fully elucidated. This study characterized ZnO NPs by using X-ray diffraction, FT-IR spectroscopy and scanning electron microscopy. Antimicrobial activity of ZnO NPs against the clinically relevant bacteria Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and the Gram-positive model Bacillus subtilis was evaluated by performing resazurin microtiter assay (REMA) after exposure to the ZnO NPs at concentrations ranging from 0.2 to 1.4 mM. Sensitivity was observed at 0.6 mM for the Gram-negative and 1.0 mM for the Gram-positive cells. Fluorescence microscopy was used to examine the interference of ZnO NPs on the membrane and the cell division apparatus of B. subtilis (amy::pspac-ftsZ-gfpmut1) expressing FtsZ-GFP. The results showed that ZnO NPs did not interfere with the assembly of the divisional Z-ring. However, 70% of the cells exhibited damage in the cytoplasmic membrane after 15 min of exposure to the ZnO NPs. Electrostatic forces, production of Zn2+ ions and the generation of reactive oxygen species were described as possible pathways of the bactericidal action of ZnO. Therefore, understanding the bactericidal MOA of ZnO NPs can potentially help in the construction of predictive models to fight bacterial resistance.

Green Manure Species for Phytoremediation of Soil With Tebuthiuron and Vinasse.

Tebuthiuron is often used to control weed growth in sugarcane cultures. This herbicide is highly toxic and can persist in soil for up to 2 years according to its degradation half-life. Hence, its residual effect is highly hazardous for the environment and local habitants via leaching, surface runoff. Screening out of species of green manure as potential phytoremediators for tebuthiuron in soil, with and with no vinasse, accordingly is the scientific point of this study. Green manure species selected for the trial in greenhouse were jack bean [Canavalia ensiformis (L.) DC.], pigeon pea [Cajanus cajan (L. Millsp.)], velvet bean [Mucuna pruriens (L.) DC.)], and millet [Pennisetum glaucum (L.) R.Br.], and Crotalaria juncea L. as bioindicator of this herbicide. The determination/quantification of height, stem diameter, and number of leaves in all plants were monitored, as well as other morphological traits for drafting any inference on biomass production. Moreover, ecotoxicity bioassays were performed from soil samples at the beginning and at the end of the experiment. Results showed preliminary evidence of effective phytoremediation capacity by M. pruriens and P. glaucum in soils with tebuthiuron, as the growth of C. juncea was sustained. Both Gompertz approach and principal component analysis predicted that these green manure species could grow healthier and for longer periods in soils containing tebuthiuron and vinasse and, thus, reduce physiological anomalies due to ecotoxicity. The implications of this study may aid in the implementation of cost-effective strategies targeting decontamination of tebuthiuron in sugarcane crops with vinasse application in fertigation.

The addition of a quaternary group in biopolymeric material increases the adsorptive capacity of Acid Blue 25 textile dye.

The quaternization of chitosan molecules creates materials with high adsorptive capacity towards textile dyes, which renders them capable of rapidly removing such dyes from a solution. In this study, a novel material was synthesized in bead form to adsorb the Acid Blue 25 textile dye. The adsorption isotherms, kinetics, and thermodynamics of this new material were investigated. The beads were further characterized by FT-IR and SEM studies, as well as their rheological behavior. Bioassays with Daphnia similis analyzed the toxicity of the dye before and after treatments. The Freundlich isotherm model fitted to all the adsorption data in a pH range from 2.50 to 8.50. Kinetic studies showed that adsorption was ruled by an intraparticle diffusion process and reached equilibrium in 270 min, as 39.527 µg mg-1 of dye was sorbed to the beads. Thermodynamic studies showed that adsorption was a spontaneous and endothermic process. Thermodynamics also confirmed that the adsorption was proportionally influenced by higher temperatures. The FT-IR spectroscopy identified the adsorbate/adsorbent binding sites, thus confirming the occurrence of chemisorption. Post-treatment bioassays found a significant decrease in toxicity, obtaining just 10% of D. similis mortality after adsorption treatments. Therefore, the synthesized beads from this research can potentially be applied to the treatment of textile effluents.

Fluorinated waste and firefighting activities: biodegradation of hydrocarbons from petrochemical refinery soil co-contaminated with halogenated foams.

Perfluorinated compounds, including fluorotelomers, are important constituents of firefighting foams to extinguish fuel fires in the petrochemical industry, airports, and at fire-training sites. In this study, we monitored the biodegradation process in a co-contamination scenario with monoaromatic hydrocarbons commonly found in fuels (benzene, toluene) and fluorotelomers. The CO2 production rates were evaluated by a factorial design taking into account the effect of seasonality at in situ natural attenuation processes. Headspace analysis by gas chromatography with a thermal conductivity detector (GC-TCD) was applied to detect CO2 production, whereas monoaromatics were analyzed by gas chromatography coupled to mass spectrometry (GC-MS). According to our results, seasonality had a detectable effect during summer, yielding different CO2 production rates. Higher temperatures increased CO2 production rate, while higher concentrations of fluorotelomer inhibited the biodegradation process. On average, benzene and toluene were depleted 17.5 days earlier in control assays without fluorotelomers. Toluene removal efficiency was also notably higher than benzene. The noticeable decrease in degradation rates of monoaromatics was caused by perfluorinated compounds that are possibly linked to metabolic inhibition mechanisms. Fluorotelomer diminished catabolism in all of our batch cultures. In addition to this, an alternative production of by-products could be detected. Thus, we propose that transient components of the benzene and toluene degradation may be differentially formed, causing the benzene, toluene, and perfluorinated co-contaminations to go through switched metabolic stages under the presence of fluoride in a contamination scenario.

Electrochemically assisted photocatalysis: Highly efficient treatment using thermal titanium oxides doped and non-doped electrodes for water disinfection.

Electrochemically assisted photocatalysis (by electronic drainage) is a highly promising method for disinfection of water. In this research, the efficiency of photolytic oxidation using UV-A radiation and electrochemically assisted photocatalysis (with electric potential of 1.5 V) was studied by using electrodes prepared by thermal treatment and doped with silver, for inactivation of Escherichia coli and Staphylococcus aureus. The Chick-Watson microorganism inactivation model was applied and the electrical energy consumption of the process was calculated. It was observed no significant inactivation of microorganisms when UV-A light or electric potential were applied separately. However, the electrochemically assisted photocatalytic process, with Ag-doped electrode completely inactivated the microbial population after 10 (E. coli) and 60 min (S. aureus). The best performing non-doped electrodes achieved 52.74% (E. coli) and 44.09% (S. aureus) inactivation rates after 60 min. Thus, electrochemically assisted photocatalytic activity was not only effective for the inactivation of microorganisms, but also notably low on electrical energy consumption during the treatment due to small current and low electric potential applied.

The effects of fluoride based fire-fighting foams on soil microbiota activity and plant growth during natural attenuation of perfluorinated compounds.

The use of fluoride based foams increases the effectiveness of fire-fighting operations, but they are also accompanied by major drawbacks regarding environmental safety of perfluorinated compounds (PFCs). The main concern with PFCs release is due to their well-known persistence and bioaccumulative potential, as they have been detected in many environmental samples. There is a significant knowledge gap on PFC toxicity to plants, even though such data could be useful towards bioremediation procedures. It is consensus that a realistic assessment of fire-fighting foam toxicity should cover as many test organisms as possible, however, few studies combine the performance of ecotoxicological tests with a detailed study of microbial communities in soil contaminated with firefighting foams. Our research evaluated the effects of natural attenuation of PFCs on the development of arugula and lettuce seeds. The effects of variable PFCs amounts were also observed in soil microbiota using the 2,6 dichlorophenol-indophenol redox dye as microbial metabolism indicator. We aimed to determine whether aqueous film forming foams toxicity increased or decreased over time in a simulated contamination scenario. We argued that the long-term biotransformation of fire-fighting foams should be taken in to account when evaluating toxicity, focusing on a time-based monitoring analysis, since potentially toxic intermediates may be formed though biodegradation. The phyto-toxicity of PFCs to lettuce and arugula was high, increasing as a function of the concentration and decreasing as a function of exposure time to the environment. However, very specific concentrations throughout biodegradation result in the formation of non-inhibiting intermediates. Therefore, variable biodegradation-dependent germination rates may be misleading on non-time-based monitoring approaches. Also, the low phyto-toxicity after 240days does not exclude the potential for PFC bioaccumulation in plants. We also proposed that the colorimetric data modelling could also establish a novel toxicity parameter to evaluate the release impacts to soil and biota. The combined assays allowed the monitoring of PFCs during long-term exposition to plants as well as their immediate effects on the same soil microbiota.

Metabolical shifts towards alternative BTEX biodegradation intermediates induced by perfluorinated compounds in firefighting foams.

The type and concentration of perfluorinated compounds (PFCs) can induce different types of enzymes and promote alternate patterns of BTEX transformation. However, it is not known how the presence of active fluorocarbon-degrading microbial populations affects the transformation of BTEX. In addition to chemical analysis at the molecular level, our research approached the aqueous film forming fire-fighting foams (AFFF) and BTEX co-contamination at a large-scale with respirometers to quantify the total microbial metabolism of soil via CO2 output levels. The intended outcome of this research was to obtain and characterize shifts in BTEX degradation at a set realistic environmental condition while measuring byproducts and CO2 production. Both methodologies complimentarily provided an in-depth knowledge of the environmental behavior of fire-fighting foams. The biodegradation was monitored using headspace sampling and two types of gas chromatography: thermal conductivity detector and flame ionization detector. Headspace samples were periodically withdrawn for BTEX biodegradation and CO2 production analysis. Our research suggests the discovery of an altered metabolic pathway in aromatic hydrocarbons biodegradation that is directly affected by fluorinated substances. The fluorinated compounds affected the BTEX biodegradation kinetics, as PFCs may contribute to a shift in styrene and catechol concentrations in co-contamination scenarios. A faster production of styrene and catechol was detected. Catechol is also rapidly consumed, thus undergoing further metabolic stages earlier under the presence of PFCs. The release of AFFF compounds not only changes byproducts output but also drastically disturbs the soil microbiota according to the highly variable CO2 yields. Therefore, we observed a high sensitivity of microbial consortia due to PFCs in the AFFF formulation, therefore shifting their BTEX degradation routes in terms of intermediate products concentration.

Assessing Bacillus subtilis biosurfactant effects on the biodegradation of petroleum products.

Microbial pollutant removal capabilities can be determined and exploited to accomplish bioremediation of hydrocarbon-polluted environments. Thus, increasing knowledge on environmental behavior of different petroleum products can lead to better bioremediation strategies. Biodegradation can be enhanced by adding biosurfactants to hydrocarbon-degrading microorganism consortia. This work aimed to improve petroleum products biodegradation by using a biosurfactant produced by Bacillus subtilis. The produced biosurfactant was added to biodegradation assays containing crude oil, diesel, and kerosene. Biodegradation was monitored by a respirometric technique capable of evaluating CO2 production in an aerobic simulated wastewater environment. The biosurfactant yielded optimal surface tension reduction (30.9 mN m(-1)) and emulsification results (46.90% with kerosene). Biodegradation successfully occurred and different profiles were observed for each substance. Precise mathematical modeling of biosurfactant effects on petroleum degradation profile was designed, hence allowing long-term kinetics prediction. Assays containing biosurfactant yielded a higher overall CO2 output. Higher emulsification and an enhanced CO2 production dataset on assays containing biosurfactants was observed, especially in crude oil and kerosene.

Screening the toxicity and biodegradability of petroleum hydrocarbons by a rapid colorimetric method.

Crude oil and petroleum products have a wide variety of hazardous components with high toxicity and low biodegradability. Certain dyes change their colors by intercepting electron transfer reactions during the transformation processes. This study applied resazurin and 2,6-dichlorophenol-indophenol indicators for a rapid screening biodegradation capability and toxicity response to various petroleum products such as motor oil, diesel, gasoline, and phenol. Colorimetry tests were performed in test tubes, and the absorbance values were measured over time. We observed different discoloration profiles after degradation tests using Bacillus subtilis inoculum. Phytotoxicity assays were also performed to compare colorimetric screening assays with a conventional toxicity testing with plants (seed germination). The results indicated that biotransformation of oils can increase its overall toxicity. Intermediate byproducts can be formed through biodegradation and thereby increase the toxicity of oils. The assessment of acute toxicity has shown that phenol is extremely toxic to petroleum-biodegrading microbial communities. Low molecular-weight gasoline was considered biodegradable, but it also exhibited a high acute toxic effect, mainly due to its high solubility and the presence of more volatile compounds that can penetrate cells and potentially damage cellular structures.

Biodegradation and toxicological evaluation of lubricant oils

The aim of this work was to compare different toxicity levels of lubricant oils. The tests were performed using the earthworm (Eisenia andrei), arugula seeds (Eruca sativa) and lettuce seeds (Lactuca sativa), with three types of contaminants (mineral lubricant oil, synthetic lubricant oil and used lubricant oil) for various biodegradation periods in the soil. The toxicity tests indirectly measured the biodegradation of the contaminants. The samples were analyzed at t0, t60, t120 and t180 days of biodegradation. The used lubricant oil was proved very toxic in all the tests and even after biodegradation its toxicity was high. The mineral and synthetic oils were biodegraded efficiently in the soil although their toxicity did not disappear completely after 180 days.

Toxicity and biodegradation in sandy soil contaminated by lubricant oils.

The objective of this study was to evaluate the environmental behavior of different types of automotive lubricant oils. Based on respirometry assays the biodegradability was monitored, and toxicological tests were executed to assess the lubricants toxicity before and after microbial activity. Used oil was the most biodegradable, however, it was the most toxic. Also, all lubricants presented toxicity even after biodegradation due to 40% Eruca sativa germination inhibition and a low LC50 to Eisenia foetida (0.50-0.25 mL). Moreover, used automotive lubricants have a high toxicity because of polycyclic aromatic hydrocarbons concentration that establishes them as a potential carcinogen.