Benzalkonium Chlorides Research Articles

Bactericidal Properties of Modular Protective Materials

Previously, the principle of constructing modular materials with specified properties was developed, according to which organometallic composites with nanoscale metal complexes introduced into them were applied to a unified fabric platform. The aim of the work was to study the properties of a unified fabric platform and to establish the possibility of giving protective bactericidal properties to fibrous materials (tissues). Such a platform has high stability and good bactericidal activity. It is shown in the article that the most significant indicators for tissue biocide were those reflecting the particle size of the dispersed phase, particle size distribution, the chemical composition of the dispersed phase, the qualitative and quantitative ratio of impurities in the dispersion medium, the concentration of particles of the dispersed phase in the dispersion medium, ζ-potential of particles of the dispersed phase; wettability of the fibers of the material by the main component of the dispersion medium (solvent), volatility of the main component of the dispersion medium (solvent). The bactericidal properties depended on the chosen method of fibrous material functionalization. Due to the principle of modular construction of materials with desired properties, it turned out to be possible to use organometallic composites with complexes of metal nanoparticles introduced into them. Studies of the biocidal activity of fibrous materials functionalized with metal nanoparticles in relation to different types of bacteria showed that it is possible to achieve characteristics comparable or even exceeding the known characteristics of antimicrobial drugs (benzetonium and benzalkonium chlorides) currently used in medical practice. As a unified fabric platform on which special modules are applied, it is proposed to use para–aramid protective fabric (Rusar fiber), as well as other types of fabrics - mixed aramid-viscose, aramid-cotton, aramid-polyacrylate, metaaramide (Nomex fiber). Approaches to giving materials (tissues) bactericidal protective properties are determined

Metabolism of Benzalkonium Chloride by CYP‐Mediated ω‐Oxidation and C‐C Cleavage Followed by β‐Oxidation in Humans

IntroductionBenzalkonium chlorides (BACs) are widely used quaternary ammonium disinfectants. A recent study found that median levels of BACs in human blood have increased 174% during COVID from pre‐COVID levels, with BACs being detected in 98% of blood samples. Although the parent BACs are not readily excreted into urine, we have identified several BAC metabolites in anonymous human urine samples. Formation of these metabolites requires ω‐oxidation and oxidative C‐C cleavage of BAC alkyl chains followed by β‐oxidation to produce a series of chain‐shortened carboxylic acid (COOH) BAC metabolites.Here, we aim to elucidate the metabolic route(s) that can account for the observed urinary metabolites of BACs. Our approach includes LC‐MS‐based investigation of metabolite profiles in microsomes, hepatocytes, and recombinant CYPs in comparison with those observed in human urine. BACs of the alkyl chain lengths found in commercial mixtures (C12, C14, and C16) served as substrates. Authentic metabolite standards were synthesized and confirmed by NMR and LC‐MS/MS. Selective CYP inhibitors were employed to assign specific CYP isoform contributions to metabolite formation.ResultsAs an extension of our previous work, we confirmed that NADPH‐dependent ω‐oxidation in microsomes and recombinant CYPs produced ω‐OH and ω‐COOH metabolites, as well as ω‐1 oxidized products, of all BAC chain lengths. We further found that the responsible CYPs (2D6, 4F2, 4F11, and 4F12) are all capable of performing C‐C cleavage of BAC side chains’ terminal carbons. The resulting products were chain‐shortened ω‐COOH BACs having lost 1 or 2 carbons (‐CH2 or ‐C2H4). In hepatocytes, subsequent β‐oxidation of the ω‐COOH C10, C12, C14, and C16 BAC metabolites (having lost 0 or 2 carbons during CYP metabolism) produces a series of even‐carbon ω‐COOH products (C4, C6, and C8) given the successive 2 carbon removal (‐C2H4) from the even‐carbon starting chain lengths. Additionally, hepatocytes produce a series of odd‐carbon ω‐COOH products (C5, C7, and C9) that logically originate from β‐oxidation of ω‐COOH C11, C13, and C15 BAC metabolites (having lost 1 carbon during CYP metabolism). The ω‐COOH BAC metabolites produced in hepatocytes were the same as those detected in human urine samples, and the relative abundance among the various chain lengths of ω‐COOH products was similar between human hepatocytes and urine. In most urine samples, C8, C10, and C12 were the most abundant COOH metabolites of even‐carbon length, and C9 was most abundant among the odd‐carbon series. In hepatocytes, addition of HET0016 and quinidine to inhibit CYP4F/CYP2D6 abolished all metabolite formation, including the β‐oxidation products.ConclusionThe above data confirm that CYP4F and/or CYP2D6 are required to initiate BAC metabolism. The relative abundance of ω‐ and β‐oxidized products (ω‐COOH BACs C4 ‐ C16) observed in urine was consistent with the human cellular metabolism of BACs observed in hepatocytes. While parent BACs are commonly found in human blood, they are not readily excreted to urine. Thus, we propose to expand monitoring of human urine samples for chain‐shortened ω‐COOH BAC metabolites as a practical surrogate for assessing BAC exposure in the general population.

Assessment of Physicochemical, Microbiological and Toxicological Hazards at an Illegal Landfill in Central Poland.

This study aimed to assess the physicochemical, microbiological and toxicological hazards at an illegal landfill in central Poland. The research included the analysis of airborne dust (laser photometer), the number of microorganisms in the air, soil and leachate (culture method) and the microbial diversity in the landfill environment (high-throughput sequencing on the Illumina Miseq); the cytotoxicity (PrestoBlue) and genotoxicity (alkaline comet assay) of soil and leachate were tested. Moreover, an analysis of UHPLC-Q-ToF-UHRMS (ultra-high-performance liquid chromatography-quadrupole-time-of-flight ultrahigh-resolution mass spectrometry) was performed to determine the toxic compounds and microbial metabolites. The PM1 dust fraction constituted 99.89% and 99.99% of total dust and exceeded the threshold of 0.025 mg m−3 at the tested locations. In the air, the total number of bacteria was 9.33 × 101–1.11 × 103 CFU m−3, while fungi ranged from 1.17 × 102 to 4.73 × 102 CFU m−3. Psychrophilic bacteria were detected in the largest number in leachates (3.3 × 104 to 2.69 × 106 CFU mL−1) and in soil samples (8.53 × 105 to 1.28 × 106 CFU g−1). Bacteria belonging to Proteobacteria (42–64.7%), Bacteroidetes (4.2–23.7%), Actinobacteria (3.4–19.8%) and Firmicutes (0.7–6.3%) dominated. In the case of fungi, Basidiomycota (23.3–27.7%), Ascomycota (5.6–46.3%) and Mortierellomycota (3.1%) have the highest abundance. Bacteria (Bacillus, Clostridium, Cellulosimicrobium, Escherichia, Pseudomonas) and fungi (Microascus, Chrysosporium, Candida, Malassezia, Aspergillus, Alternaria, Fusarium, Stachybotrys, Cladosporium, Didymella) that are potentially hazardous to human health were detected in samples collected from the landfill. Tested leachates and soils were characterised by varied cyto/genotoxins. Common pesticides (carbamazepine, prometryn, terbutryn, permethrin, carbanilide, pyrethrin, carbaryl and prallethrin), quaternary ammonium compounds (benzalkonium chlorides), chemicals and/or polymer degradation products (melamine, triphenylphosphate, diphenylphtalate, insect repellent diethyltoluamide, and drugs (ketoprofen)) were found in soil and leachate samples. It has been proven that the tested landfill is the source of the emission of particulate matter; microorganisms (including potential pathogens) and cyto/genotoxic compounds.

Chronic Effects of Benzalkonium Chlorides on Short Chain Fatty Acids and Methane Production in Semi-Continuous Anaerobic Digestion of Waste Activated Sludge

Chronic Effects of Benzalkonium Chlorides on Short Chain Fatty Acids and Methane Production in Semi-Continuous Anaerobic Digestion of Waste Activated Sludge

Adsorption of benzalkonium chlorides onto polyethylene microplastics: Mechanism and toxicity evaluation

Usage of disposable plastic products and disinfectants has been skyrocketing due to the COVID-19 pandemic. The random disposal of plastic products may result in greater microplastic pollution. Benzalkonium chloride is known as one of the most common ingredients of disinfectants. In this study, the adsorption behavior of benzalkonium chlorides (BAC12, BAC14, BAC16) on polyethylene microplastics (PE-MPs) and the combined toxic effects were investigated using batch adsorption experiment and Daphnia magna. The results showed that PE-MPs had strong adsorption capacity for BACs and the adsorption capacity increased (11.03–22.77 mg g−1) with their octanol-water distribution coefficients. The effect of pH was negligible while dissolved organic matter inhibited the adsorption. A slightly inverse relationship between particle size of PE-MPs and adsorption was observed. Additionally, the MP aging with UV/H2O2 increased the adsorption of BAC12 but decreased that of relatively hydrophobic BAC14 and BAC16. The survival rate of Daphnia magna increased up to 100% in the presence of PE-MPs depending upon their adsorption capacities, suggesting that PE-MPs do not act as a carrier but rather as a scavenger for BACs. This study provides important information necessary for environmental risk assessment with regard to the combined pollution of MPs and toxic chemicals.

Adsorption of benzalkonium chlorides onto powdered activated carbon: mechanisms and detoxification

Because disinfectants have been essential during the COVID-19 pandemic, the global demand for benzalkonium chlorides (BACs) has significantly increased. BACs can inactivate coronaviruses, but are known as toxic. In this study, we investigated the adsorption mechanisms of BAC12, BAC14, and BAC16 in water using powdered activated carbon (PAC). The effects of the reaction time, pH, and temperature on the adsorption kinetics of BACs were examined. The adsorption reaction followed pseudo-second-order kinetics, and better fitted to the Langmuir isotherm than the Freundlich isotherm. The best adsorption of BACs was achieved at neutral pH conditions. Thermodynamic analysis revealed that adsorption of BACs onto PAC is a spontaneous and endothermic process. Competitive adsorption experiments revealed that BACs with longer alkyl chains were adsorbed more effectively onto PAC than shorter alkyl chain BACs, implying that, while the electrostatic interaction is an important adsorption mechanism for BAC12, van der Waals interaction plays a more important role during the adsorption of BAC14 and BAC16. Finally, we observed the partial detoxification (69%) BAC in adsorption treated water with PAC using a Microtox test.

Benzalkonium chlorides (C12) inhibits growth but motivates microcystins release of Microcystis aeruginosa revealed by morphological, physiological, and iTRAQ investigation

Due to the large-scale outbreak of Corona Virus Disease (2019), amounts of disinfecting agents was regularly used in public environments and their potential toxicity towards organisms needed to be appreciated. Thus, one mostly used cationic disinfectant, benzalkonium chlorides (BAC(C12)), was selected to assess its potential toxicity one common cyanobacteria Microcystis aeruginosa (M. aeruginosa) in this study. The aims were to explore the toxic effect and mechanism of BAC (C12) on M. aeruginosa growth within 96 h via morphological, physiological, and the relative and absolute quantification (iTRAQ)-based quantitative proteomics variations. The results found that BAC(C12) significantly inhibited cell density of M. aeruginosa at concentrations from 1 mg/L to 10 mg/L, and the 96-h EC50 value was identified to be 3.61 mg/L. Under EC50 concentration, BAC(C12) depressed the photosynthesis activities of M. aeruginosa exhibited by 36% decline of the maximum quantum yield for primary photochemistry (Fv/Fm) value and denaturation of photosynthetic organelle, caused oxidative stress response displayed by the increase of three indexes including superoxide dismutase (SOD), malondialdehyde (MDA), and the intracellular reactive oxygen species (ROS), and destroyed the integrity of cell membranes demonstrated by TEM images and the increase of ex-cellular substances. Then, the iTRAQ-based proteomic analysis demonstrated that BAC(C12) depressed photosynthesis activities through inhibiting the expressions of photosynthetic protein and photosynthetic electron transport related proteins. The suppression of electron transport also led to the increase of superoxide radicals and then posed oxidative stress on cell. Meantime, the 63.63% ascent of extracellular microcystin production of M. aeruginosa was observed, attributing to the high expression of microcystin synthesis proteins and the damage of cell membrane. In sum, BAC(C12) exposure inhibited the growth of M. aeruginosa mainly by depressing photosynthesis, inducing oxidative stress, and breaking the cell membrane. And, it enhanced the release of microcystin from the cyanobacterial cells via up-regulating the microcystin synthesis proteins and inducing the membrane damage, which could enlarge its toxicity to aquatic species.

Responses of anaerobic digestion of waste activated sludge to long-term stress of benzalkonium chlorides: Insights to extracellular polymeric substances and microbial communities

Quaternary ammonium compounds have gained widespread attention due to their extensive enrichment in waste activated sludge (WAS) and potentially adverse effect to anaerobes. This study selected benzalkonium chlorides (BACs) as model to reveal the responses of anaerobic digestion of WAS to long-term stress of BACs. Results showed that the solubilization enhancement of WAS contributed by BACs was the acceleration of cell lysis, rather than the disruption of extracellular polymeric substances, and the accumulation improvement of short chain fatty acids (SCFAs) attributed to hydrolysis improvement and methanogenesis inhibition at either medium -or high level of BACs. In addition, a low level had no significant effect on the production of methane compared to control, with averages of 0.059 and 0.055 m3/(m3·d), respectively, whereas a medium level reduced methane production to 20% of control, and a high level almost completely inhibited methanogenesis. Correspondingly, BACs could shift microbial communities related to SCFAs and methane productions. For the bacterial community, a high level of BACs led to abundance reductions of Firmicutes, Bacteroidetes, Acidobacteria and Chloroflexi, but Synergistetes was increased to 10.5%, which was almost not detected either in control or at a low level of BACs. And for dominant archaeal community, they tended to be shifted from acetotrophic to hydrogenotrophic methanogens with BACs increasing from low to high level. These findings provided some new insights for the role of BACs in anaerobic digestion, as well as resource recovery from WAS.

Biological removal of benzalkonium chlorides from wastewater by immobilized cells of Pseudomonas sp. BIOMIG1 in an up-flow packed bed reactor

Quaternary ammonium compounds (QACs) are active ingredients of many disinfectants used against SARS-CoV-2 to control the transmission of the virus through human-contact surfaces. As a result, QAC consumption has increased more than twice during the pandemic. Consequently, the concentration of QACs in wastewater and receiving environments may increase. Due to their antimicrobial activity, high levels of QACs in wastewater may cause malfunctioning of biological treatment systems resulting in inadequate treatment of wastewater. In this study, a biocatalyst was produced by entrapping Pseudomonas sp. BIOMIG1 capable of degrading QACs in calcium alginate. Bioactive 3-mm alginate beads degraded benzalkonium chlorides (BACs), a group of QACs, with a rate of 0.47 µM-BACs/h in shake flasks. A bench-scale continuous up-flow reactor packed with BIOMIG1-beads was operated over one and a half months with either synthetic wastewater or secondary effluent containing 2–20 µM BACs at an empty bed contact time (EBCT) ranging between 0.6 and 4.7 h. Almost complete BAC removal was achieved from synthetic and real wastewater at and above 1.2 h EBCT without aeration and effluent recirculation. The microbial community in beads dominantly composed of BIOMIG1 with trace number of Achromobacter spp. after the operation of the reactor with the real wastewater, suggesting that BIOMIG1 over-competed native wastewater bacteria during the operation. This reactor system offers a low cost and robust treatment of QACs in wastewater. It can be integrated to conventional treatment systems for efficient removal of QACs from the wastewater, especially during the pandemic period.

Microextraction–Colorimetric (Fluorimetric) Determination of Cationic and Anionic Surfactants in Food Products

A method is proposed for the determination of cationic and anionic surfactants in food products based on the use of dispersive liquid–liquid microextraction of surfactant ion pairs with organic reagents (eosin and acridine yellow) and measurements of the colorimetric parameters of the fluorescence of extracts using a smartphone. Upon the irradiation of the extracts of ion pairs anionic surfactant–acridine yellow and cationic surfactant–eosin with ultraviolet light (365 nm), green and yellow fluorescence were observed, respectively. The analytical signal (Ar) was the value of the colorimetric parameters in the RGB system: Ar = $$\sqrt {{{{{\text{(}}{{R}_{{\text{0}}}} - {{R}_{x}}{\text{)}}}}^{2}}{\text{ + (}}{{G}_{{\text{0}}}} - {{G}_{x}}{{{\text{)}}}^{2}}{\text{ + (}}{{B}_{{\text{0}}}} - {{B}_{x}}{{{\text{)}}}^{2}}} .$$ Procedures for determining the total amount of surfactants in food products (milk, vegetables and fruits, meat, and drinking water) are developed using an example of cetylpyridinium, myristalconium, benzalkonium, didecyldimethylammonium, alkyldimethyl(ethylbenzyl)ammonium, dodecyl sulfate and sodium alkylbenzenesulfonate chlorides. The limits of detection and quantification are in the ranges 0.005–0.05 and 0.01–0.1 mg/L, respectively. Calibration graphs are linear in the concentration range 0.01–1 mg/L with approximation confidence coefficients ≥0.99. The duration of analysis is 20–30 min; the relative standard deviation of the results of analysis does not exceed 0.24.

Benzalkonium Chloride Disinfectants Induce Apoptosis, Inhibit Proliferation, and Activate the Integrated Stress Response in a 3-D in Vitro Model of Neurodevelopment.

We previously found that the widely used disinfectants, benzalkonium chlorides (BACs), alter cholesterol and lipid homeostasis in neuronal cell lines and in neonatal mouse brains. Here, we investigate the effects of BACs on neurospheres, an in vitro three-dimensional model of neurodevelopment. Neurospheres cultured from mouse embryonic neural progenitor cells (NPCs) were exposed to increasing concentrations (from 1 to 100 nM) of a short-chain BAC (BAC C12), a long-chain BAC (BAC C16), and AY9944 (a known DHCR7 inhibitor). We found that the sizes of neurospheres were decreased by both BACs but not by AY9944. Furthermore, we observed potent inhibition of cholesterol biosynthesis at the step of DHCR7 by BAC C12 but not by BAC C16, suggesting that cholesterol biosynthesis inhibition is not responsible for the observed reduction in neurosphere growth. By using immunostaining and cell cycle analysis, we found that both BACs induced apoptosis and decreased proliferation of NPCs. To explore the mechanisms underlying their effect on neurosphere growth, we carried out RNA sequencing on neurospheres exposed to each BAC at 50 nM for 24 h, which revealed the activation of the integrated stress response by both BACs. Overall, these results suggest that BACs affect neurodevelopment by inducing the integrated stress response in a manner independent of their effects on cholesterol biosynthesis.

Identification of core micropollutants of Ergene River and their categorization based on spatiotemporal distribution

Ergene River is heavily utilized for irrigation of fields to grow the main stocks of rice, wheat, and sunflower of Turkey also exported to Europe; therefore, monitoring the river's water quality is crucial for public health. Although the river quality is routinely monitored, the evaluation of pollution based on micropollutants is limited. In this study, we measured 222 organic micropollutants in 300 samples collected from 75 different locations on the Ergene River between August 2017 and May 2018 using direct injection liquid chromatography-tandem spectrometry with optimized scheduled multiple reaction monitoring. In total, 165 micropollutants were detected at a range of concentrations between 1.90 ng/L and 1824.55 μg/L. Sixty-three chemical substances were recurrent micropollutants that were detected at least one location in all seasons. Among them, 41 chemical substances were identified as the core micropollutants of the Ergene River using data-driven clustering methods. Hexa(methoxymethyl)melamine, benzotriazoles, and benzalkonium chlorides were frequently detected core micropollutants with an industrial origin. Besides, diuron, carbendazim, and cadusafos were common pesticides in the river. Core micropollutants were further categorized based on their type of source and environmental behavior using Kurtosis of concentration and load data obtained for each micropollutant. As a result, the majority of the core micropollutants are recalcitrant chemicals either released from a specific source located upstream of the river or have urban and agricultural sources dispersed on the watershed. In this study, we assessed the current state of pollution in the Ergene River at the micropollutant level with a very high spatial resolution and developed a statistical approach to categorize micropollutants that can be used to monitor the extent of pollution and track pollution sources in the river.

FENTON OXIDATION AS A STRATEGY TO PRESERVE THE BIOMASS IN THE ACTIVATED SLUDGE SYSTEM

Wastewaters containing biocides constitute an increasing environmental pollution concern. In this work, the feasibility of implementing a pre-treatment based on the Fenton process to minimize the negative impact of biocide compounds, such as benzalkonium chlorides (BAC), on the activated sludge system was studied. The behavior of the microbial community in the presence of a BAC solution untreated (BAC100) or pre-treated by homogeneous Fenton oxidation (BAC100/HF) was analyzed. The addition of BAC100 to the activated sludge system caused a deleterious effect. The cellular lysis process caused a 30% decrease in biomass concentration. The inhibition of respiratory activity was 73%. In contrast, BAC100/HF caused no significant decrease in the biomass concentration or detectable inhibition of the respiratory activity. Besides, the consumption of easily oxidizable products was observed. Results indicated that the homogeneous Fenton process as a pre-treatment of wastewaters containing BAC could become a feasible alternative to protect active biomass in biological treatment systems.

Biocidal spray product exposure: Measured gas, particle, and surface concentrations compared with spray model simulations

The purpose of the study was to compare measured air and surface concentrations after application of biocidal spray products with concentrations simulated with the ConsExpo Web spray simulation tool. Three different biocidal spray products were applied in a 20 m3 climate test chamber with well-controlled environmental conditions (22 ± 1 °C, 50 ± 2% relative humidity, and air exchange rate of 0.5 h−1). The products included an insect spray in a pressurized spray can, another insect spray product, and a disinfectant, the latter two applied separately with the same pumped spray device. The measurements included released particles, airborne organic compounds in both gas and particle phase, and surface concentrations of organic compounds on the wall and floor in front of the spraying position and on the most remote wall. Spraying time was a few seconds and the air concentrations were measured by sampling on adsorbent tubes at 9–13 times points during 4 hr after spraying. The full chamber experiment was repeated 2–3 times for each product. Due to sedimentation the concentrations of the particles in air decayed faster than explained by the air exchange rate. In spite of that, the non-volatile benzalkonium chlorides in the disinfectant could be measured in the air more than 30 min after spraying. ConsExpo Web simulated concentrations that were about half of the measured concentrations of the active substances when as many as possible of the default simulation parameters were replaced by the experimental values. ConsExpo Web was unable to simulate the observed faster decay of the airborne concentrations of the active substances, which might be due to underestimation of the gravitational particle deposition rates. There was a relatively good agreement between measured surface concentrations on the floor and calculated values based on the dislodgeable amount given in the selected ConsExpo Web scenarios. It is suggested to always supplement simulation tool results with practical measurements when assessing the exposure to a spray product.

Metabolism of Benzalkonium Chlorides by Human Hepatic Cytochromes P450.

Benzalkonium chlorides (BACs) are widely used as disinfectants in cleaning products, medical products, and the food processing industry. Despite a wide range of reported toxicities, limited studies have been conducted on the metabolism of these compounds in animal models and none in human-derived cells or tissues. In this work, we report on the metabolism of BACs in human liver microsomes (HLM) and by recombinant human hepatic cytochrome P450 (CYP) enzymes. BAC metabolism in HLM was NADPH-dependent and displayed apparent half-lives that increased with BAC alkyl chain length (C10 < C12 < C14 < C16), suggesting enhanced metabolic stability of the more lipophilic, longer chain BACs. Metabolites of d7-benzyl labeled BAC substrates retained all deuteriums and there was no evidence of N-dealkylation. Tandem mass spectrometry fragmentation of BAC metabolites confirmed that oxidation occurs on the alkyl chain region. Major metabolites of C10-BAC were identified as ω-hydroxy-, (ω-1)-hydroxy-, (ω, ω-1)-diol-, (ω-1)-ketone-, and ω-carboxylic acid-C10-BAC by liquid chromatography-mass spectrometry comparison with synthetic standards. In a screen of hepatic CYP isoforms, recombinant CYP2D6, CYP4F2, and CYP4F12 consumed substantial quantities of BAC substrates and produced the major microsomal metabolites. The use of potent pan-CYP4 inhibitor HET0016, the specific CYP2D6 inhibitor quinidine, or both confirmed major contributions of CYP4- and CYP2D6-mediated metabolism in the microsomal disappearance of BACs. Kinetic characterization of C10-BAC metabolite formation in HLM demonstrated robust Michaelis-Menten kinetic parameters for ω-hydroxylation (Vmax = 380 pmol/min/mg, Km = 0.69 μM) and (ω-1)-hydroxylation (Vmax = 126 pmol/min/mg, Km = 0.13 μM) reactions. This work illustrates important roles for CYP4-mediated ω-hydroxylation and CYP2D6/CYP4-mediated (ω-1)-hydroxylation during the hepatic elimination of BACs, an environmental contaminant of emerging concern. Furthermore, we demonstrate that CYP-mediated oxidation of C10-BAC mitigates the potent inhibition of cholesterol biosynthesis exhibited by this short-chain BAC.

Performance and microbial community responses of anaerobic digestion of waste activated sludge to residual benzalkonium chlorides

The emerging organic pollutants, quaternary ammonium compounds, have attracted extensive attention due to their great enrichment in waste activated sludge (WAS). This study selected benzalkonium chlorides (BACs) as model to reveal its effects of levels and alkyl chain lengths (ACLs) on methane production from anaerobic digestion of WAS. Results showed that BACs caused more release of soluble polysaccharides and proteins, increased by 42.6–55.7% and 11.5–19.4%, which were positively related to the levels of BACs. In contrast, the methanogenesis was inhibited, and a higher level or a shorter ACL led to a more significant inhibition. The maximum production of methane was 171.1 mL/g VSS in control, and reduced to 97.8, 41.5 and 7.63 mL/g VSS for ACL16, ACL14 and ACL12 at the BAC level of 25 mg/g TSS, consequently, the corresponding accumulations of short-chain fatty acids were 1.57–1.84 times higher than that of control. Moreover, the presence of BACs also affected the diversities of both bacteria and archaea involved in methane production. Compared to control, BACs reduced Firmicutes, Bacteroidetes and Chloroflexi, especially Firmicutes, with a decrease ratio of 12.6–20.2%, whereas Proteobacteria and Actinobacteria were increased. Besides, a longer ACL led to a higher enrichment of Methanomicrobia, and with the ACLs of BACs decreasing from 16 to 12, the dominant methanogens shifted from acetotrophic to mixotrophic, and further to hydrogenotrophic methanogens. The findings of this study demonstrated that both levels and ACLs of BACs could affect the performance of anaerobic digestion of WAS, as well as the microbial community.

Benzalkonium Chlorides: Uses, Regulatory Status, and Microbial Resistance.

Benzalkonium chlorides (BACs) are chemicals with widespread applications due to their broad-spectrum antimicrobial properties against bacteria, fungi, and viruses. This review provides an overview of the market for BACs, as well as regulatory measures and available data on safety, toxicity, and environmental contamination. We focus on the effect of frequent exposure of microbial communities to BACs and the potential for cross-resistant phenotypes to emerge. Toward this goal, we review BAC concentrations in consumer products, their correlation with the emergence of tolerance in microbial populations, and the associated risk potential. Our analysis suggests that the ubiquitous and frequent use of BACs in commercial products can generate selective environments that favor microbial phenotypes potentially cross-resistant to a variety of compounds. An analysis of benefits versus risks should be the guidepost for regulatory actions regarding compounds such as BACs.

Multiomics Investigation Reveals Benzalkonium Chloride Disinfectants Alter Sterol and Lipid Homeostasis in the Mouse Neonatal Brain.

Lipids are critical for neurodevelopment; therefore, disruption of lipid homeostasis by environmental chemicals is expected to have detrimental effects on this process. Previously, we demonstrated that the benzalkonium chlorides (BACs), a class of commonly used disinfectants, alter cholesterol biosynthesis and lipid homeostasis in neuronal cell cultures in a manner dependent on their alkyl chain length. However, the ability of BACs to reach the neonatal brain and alter sterol and lipid homeostasis during neurodevelopment in vivo has not been characterized. Therefore, the goal of this study was to use targeted and untargeted mass spectrometry and transcriptomics to investigate the effect of BACs on sterol and lipid homeostasis and to predict the mechanism of toxicity of BACs on neurodevelopmental processes. After maternal dietary exposure to 120 mg BAC/kg body weight/day, we quantified BAC levels in the mouse neonatal brain, demonstrating for the first time that BACs can cross the blood-placental barrier and enter the developing brain. Transcriptomic analysis of neonatal brains using RNA sequencing revealed alterations in canonical pathways related to cholesterol biosynthesis, liver X receptor-retinoid X receptor (LXR/RXR) signaling, and glutamate receptor signaling. Mass spectrometry analysis revealed decreases in total sterol levels and downregulation of triglycerides and diglycerides, which were consistent with the upregulation of genes involved in sterol biosynthesis and uptake as well as inhibition of LXR signaling. In conclusion, these findings demonstrate that BACs target sterol and lipid homeostasis and provide new insights for the possible mechanisms of action of BACs as developmental neurotoxicants.

Influence of in Vitro Assay Setup on the Apparent Cytotoxic Potency of Benzalkonium Chlorides.

The nominal concentration is generally used to express concentration–effect relationships in in vitro toxicity assays. However, the nominal concentration does not necessarily represent the exposure concentration responsible for the observed effect. Surfactants accumulate at interphases and likely sorb to in vitro system components such as serum protein and well plate plastic. The extent of sorption and the consequences of this sorption on in vitro readouts is largely unknown for these chemicals. The aim of this study was to demonstrate the effect of sorption to in vitro components on the observed cytotoxic potency of benzalkonium chlorides (BAC) varying in alkyl chain length (6–18 carbon atoms, C6–18) in a basal cytotoxicity assay with the rainbow trout gill cell line (RTgill-W1). Cells were exposed for 48 h in 96-well plates to increasing concentration of BACs in exposure medium containing 0, 60 μM bovine serum albumin (BSA) or 10% fetal bovine serum (FBS). Before and after exposure, BAC concentrations in exposure medium were analytically determined. Based on freely dissolved concentrations at the end of the exposure, median effect concentrations (EC50) decreased with increasing alkyl chain length up to 14 carbons. For BAC with alkyl chains of 12 or more carbons, EC50’s based on measured concentrations after exposure in supplement-free medium were up to 25-times lower than EC50’s calculated using nominal concentrations. When BSA or FBS was added to the medium, a decrease in cytotoxic potency of up to 22 times was observed for BAC with alkyl chains of eight or more carbons. The results of this study emphasize the importance of expressing the in vitro readouts as a function of a dose metric that is least influenced by assay setup to compare assay sensitivities and chemical potencies.

Electrochemical Analysis of Aqueous Benzalkonium Chloride Micellar Solution and Its Mediated Electrocatalytic De-Chlorination Application

The physicochemical properties of biologically important benzalkonium chlorides (BKCs) and the effects of its structure on the de-chlorination of allyl chloride was studied by electrogenerated [Co(I)(bipyridine)3]+ (Co(I)) using an electrochemical technique. The results of [Co(II)(bipyridine)3]2+ (Co(II)) cyclic voltammetry in the presence of BKC demonstrates Co(II)/Co(III) redox couple for physicochemical analysis of BKC and Co(II)/Co(I) redox couple for catalytic application. Cyclic voltammetry over a range of scan rates and BKC concentrations revealed the BKC-bound Co(II)/Co(III) micelles showed that the identification of cmc and association of the probe Co(II) species, associated more in the hydrophobic region. In addition, change in diffusion coefficient value of Co(II)/Co(III) with BKC concentration demonstrates the association of Co(II) in micellar hydrophobic region. The beneficial effects of BKC could be accounted for by considering the benzyl headgroup-Co (II) precatalyst-volatile organic compounds (VOCs) (allyl chloride here) substrate interaction. Chromatography/mass spectroscopy (GC/MS) revealed 100% complete de-chlorination of allyl chloride accompanied by three non-chloro products. This is the first report of benzyl headgroup-induced micellar enhancement by an electrochemical method, showing that it is possible to use hydrophobic benzyl headgroup-substitution to tune the properties of micelles for various applications.