Carboxylic Acid Functional Groups Research Articles

Real-Time Identification of Aerosol-Phase Carboxylic Acid Production Using Extractive Electrospray Ionization Mass Spectrometry.

Comprehensive identification of aerosol sources and their constituent organic compounds requires aerosol-phase molecular-level characterization with a high time resolution. While real-time chemical characterization of aerosols is becoming increasingly common, information about functionalization and structure is typically obtained from offline methods. This study presents a method for determining the presence of carboxylic acid functional groups in real time using extractive electrospray ionization mass spectrometry based on measurements of [M - H + 2Na]+ adducts. The method is validated and characterized using standard compounds. A proof-of-concept application to α-pinene secondary organic aerosol (SOA) shows the ability to identify carboxylic acids even in complex mixtures. The real-time capability of the method allows for the observation of the production of carboxylic acids, likely formed in the particle phase on short time scales (<120 min). Our research explains previous findings of carboxylic acids being a significant component of SOA and a quick decrease in peroxide functionalization following SOA formation. We show that the formation of these acids is commensurate with the increase of dimers in the particle phase. Our results imply that SOA is in constant evolution through condensed-phase processes, which lower the volatility of the aerosol components and increase the available condensed mass for SOA growth and, therefore, aerosol mass loading in the atmosphere. Further work could aim to quantify the effect of particle-phase acid formation on the aerosol volatility distributions.

Evidences for the influence from key chemical structures of per- and polyfluoroalkyl substances on their environmental behaviors

This study carried out the atmospheric and precipitation observation in Beijing for nearly one year, and firstly simultaneously observed the pollution characteristics of PFASs and their main isomers, focusing on their gas-particle partitioning mechanism and dry and wet deposition characteristics. After deducting PFASs in the aqueous phase of particulate matter, the gas-particle partitioning coefficients (−7.04 to −5.49) were about 3–4 units smaller than before (−2.77 to −1.51), and all were smaller than 0, which indicated that each PFAS and isomer were more distributed in the gas phase. Dry deposition was dominant in the atmospheric deposition of each PFAS and isomer with relative contribution of 66 ± 17%, but the relative contribution of dry deposition was significantly different. It was found that the gas-particle partitioning coefficient can be influenced by key chemical structures such as carbon chain length, functional group type, and isomer structure. Furthermore, the gas-particle partitioning can influence the dry and wet deposition of PFASs. Specifically, PFASs with longer carbon chains, carboxylic acid functional group (compared to sulfonic acid functional group) or PFOA branched chain structures had larger gas-particle partitioning coefficients and can be more distributed in the hydrophobic phase of particulate matter, and their relative contributions of dry deposition were smaller.

Hyaluronic acid functionalized citric acid dendrimer/UiO-66-COOH as a stable and biocompatible platform for daunorubicin delivery

This work aimed to prepare a new system for daunorubicin (DNR) delivery to improve therapeutic efficiency and decrease unwanted side effects. Typically, at first, a carboxylic acid functional group containing metal-organic framework (UiO-66-COOH) was synthesized in a simple way. Then, a third generation of citric acid dendrimer (CAD G3) was grown on it (UiO-66-COOH-CAD G3). Finally, the system was functionalized with pre-modified hyaluronic acid (UiO-66-COOH-CAD-HA). SEM analysis displayed that the synthesized particles have a spherical shape with an average particle size ranging from 260 to 280 nm. An increase in hydrodynamic diameter from 223 nm for UiO-66-COOH to 481 nm for UiO-66-COOH-CAD-HA is a sign of success in the performed reactions. Also, the average pore size was calculated at about 4.04 nm. The DNR loading efficiency of UiO-66-COOH-CAD-HA was evaluated at ∼74 % (DNR@UiO-66-COOH-CAD-HA). It was observed that the drug release rate at a lower pH is more than higher pH. The maximum hemolysis of <3 % means that the UiO-66-COOH-CAD-HA is hemocompatible. The use of DNR-loaded UiO-66-COOH-CAD-HA led to cell-killing of 77.9 % for MDA-MB 231. These results specified the great potential of UiO-66-COOH-CAD-HA for tumor drug delivery, so it could be proposed as a new carrier for anticancer agents to minimize adverse effects and improve therapeutic efficacy.

Role for Carboxylic Acid Moiety in NSAIDs: Favoring the Binding at Site II of Bovine Serum Albumin.

The molecular structures of nonsteroidal anti-inflammatory drugs (NSAIDs) vary, but most contain a carboxylic acid functional group (RCOOH). This functional group is known to be related to the mechanism of cyclooxygenase inhibition and also causes side effects, such as gastrointestinal bleeding. This study proposes a new role for RCOOH in NSAIDs: facilitating the interaction at the binding site II of serum albumins. We used bovine serum albumin (BSA) as a model to investigate the interactions with ligands at site II. Using dansyl-proline (DP) as a fluorescent site II marker, we demonstrated that only negatively charged NSAIDs such as ibuprofen (IBP), naproxen (NPX), diflunisal (DFS), and ketoprofen (KTP) can efficiently displace DP from the albumin binding site. We confirmed the importance of RCOO by neutralizing IBP and NPX through esterification, which reduced the displacement of DP. The competition was also monitored by stopped-flow experiments. While IBP and NPX displaced DP in less than 1 s, the ester derivatives were ineffective. We also observed a higher affinity of negatively charged NSAIDs using DFS as a probe and ultrafiltration experiments. Molecular docking simulations showed an essential salt bridge between the positively charged residues Arg409 and Lys413 with RCOO-, consistent with the experimental findings. We performed a ligand dissociation pathway and corresponding energy analysis by applying molecular dynamics. The dissociation of NPX showed a higher free energy barrier than its ester. Apart from BSA, we conducted some experimental studies with human serum albumin, and similar results were obtained, suggesting a general effect for other mammalian serum albumins. Our findings support that the RCOOH moiety affects not only the mechanism of action and side effects but also the pharmacokinetics of NSAIDs.

Surface functionalized visible light-responsive yttrium orthovanadate for photocatalytic hydrogen production

Yttrium orthovanadate (YVO4), a wide-bandgap photocatalyst was tuned into a visible responsive material by anchoring an organic framework on the surface of YVO4 nanoparticles using polyethyleneimine (PEI). The surface organic framework was identified as the decomposed PEI derivatives with the carbonyl and carboxylic acid functional groups by the FTIR and XPS analyses. The top of the valence band (VB) was raised and the bottom of the conduction band was moved down; hence, the band gap of YVO4 was reduced to absorb the light in the visible region for all three synthesized samples, which was confirmed by DRS UV–Vis analysis. The functional groups facilitated more water molecules on the YVO4 surface via hydrogen bonding; hence, the YVO4 surface acquired superhydrophilicity. Among the three YI, YII, and YIII samples synthesized with three different calcination temperatures of 80, 260 and 400 °C respectively, YII showed many advantageous photocatalytic properties. The optimum loading of organic compounds obtained on YII surface at 260 °C, which improved the surface area, visible light absorption, hydrophilicity, and exciton's life. Hence, YII showed a better performance of 3.75 mmol h−1g−1cat H2 production than YI and YII. This work interestingly revealed the influence of calcination temperature on surface functionalization and the performance of catalytic materials.

High‐Adhesion, Weather Resistance, Reusable PAM/Gly/Gel/TA/Fe3+ Biopolymer Dual‐Network Conductive Hydrogel for Flexible Bioelectrode

AbstractConductive hydrogel is considered a promising wearable sensor material. Developing flexible conductive hydrogel sensors with stretchability, adhesion, and stability remains challenging. In this study, a transparent, self‐adhesive, antifreeze, anti‐UV, stretchable, conductive, and reusable hydrogel with polyacrylamide/glycerol/gelatin/tannic acid/Fe3+ (PGGT‐Fe3+) structure is successfully constructed through a simple one‐pot polymerization method. The PGGT‐Fe3+ hydrogel is composed of dual networks of polyacrylamide and gelatin for organic cross‐linking, using water/glycerol as the dispersion medium, and incorporates a viscous substance: tannic acid, and a conductive substance: metal ions (Fe3+). Due to the introduction of the abundant amino, carboxylic acid, and hydroxyl functional groups on gelatin and tannic acid, the PGGT‐Fe3+ hydrogel exhibits excellent and repeatable adhesion capabilities on various surfaces (including glass, metal, plastic, and pigskin) with maximum adhesion strength of 98 kPa when attached to pigskin. Furthermore, based on the stable conductive network and high conductivity, the hydrogel not only exhibits strain sensitivity, fast response, and stability but also can stably collect epidermal bio signals. In conclusion, this work provides a new approach to the design and development of next‐generation multifunctional conductive hydrogels and opens up vast possibilities for their applications in the flexible electronics field.

Improved efficiency and stability for acridine orange sensitizers by adding electron donating/accepting π-linker moieties

Shortcomings associated with metal-free dye-sensitized solar cells can be overcome with dye modification. Using Density Functional Theory (DFT) and Time Dependent (TD-DFT), acridine orange dyes (main Donors) are modified with molecular moieties (2-Hydroxy-4-propoxyphen)(phenyl)methanone (UV absorber), 4,4′-Dimethoxydiphenylamine (Donor 1), 2-(Thiophen-2-yl)-1,3,4-oxadiazole (π-bridge), anisole (Donor 2), cyanoacetic-acid and carboxylic-acid functional groups (Acceptors 1 and 2), to form new UV Absorber-D-(A)2 and D’- π -D-(A)2 dyes with least computational costs, where acridine derivatives act as main donors. Absorption spectra, highest-occupied molecular orbitals, and lowest-unoccupied molecular orbitals are predicted by DFT and TD-DFT calculations. Ionization potential, electron affinity, electronegativity and light-harvesting efficiency are predicted with frontier-molecular orbital energies by Koopmans' theorem, using TiO2 conduction-band edge (ECB −4.0 eV) and [I-/I3-] redox-potential (-4.80 eV). Absorption redshifts with expanded range of 700 nm, and improved energy-alignment with TiO2, charge-transfer processes, redox-couple compatibility, cell stability and higher performance are all achieved by molecular level tuning of dyes.

Mid-Long Chain Dicarboxylic Acid Production via Systems Metabolic Engineering: Progress and Prospects.

Mid-to-long-chain dicarboxylic acids (DCAi, i ≥ 6) are organic compounds in which two carboxylic acid functional groups are present at the terminal position of the carbon chain. These acids find important applications as structural components and intermediates across various industrial sectors, including organic compound synthesis, food production, pharmaceutical development, and agricultural manufacturing. However, conventional petroleum-based DCA production methods cause environmental pollution, making sustainable development challenging. Hence, the demand for eco-friendly processes and renewable raw materials for DCA production is rising. Owing to advances in systems metabolic engineering, new tools from systems biology, synthetic biology, and evolutionary engineering can now be used for the sustainable production of energy-dense biofuels. Here, we explore systems metabolic engineering strategies for DCA synthesis in various chassis via the conversion of different raw materials into mid-to-long-chain DCAs. Subsequently, we discuss the future challenges in this field and propose synthetic biology approaches for the efficient production and successful commercialization of these acids.

Phytoconstituents, Fourier-Transform Infrared Characterization, and Antioxidant Potential of Ethyl Acetate Extract of Corchorus olitorius (Malvaceae)

Oxidative stress is a condition that is characterized by the generation of reactive oxygen species more than the amount endogenous antioxidants can absorb. Several diseases are associated with oxidative stress, notably during disease progression. Thus, the present study aimed to determine the phytoconstituents and antioxidant potential of the ethyl acetate leaf extract of Corchorus olitorius (ELEC). The phytochemicals were qualitatively and quantitatively determined, followed by characterization using Fourier-transform infrared (FTIR) spectroscopy. The antioxidant potential was determined in vitro. Alkaloids, saponins, and flavonoids were detected in concentrations of 8.50 ±2.65, 11.83 ±0.73, and 19.17% ±0.73, respectively. The FTIR spectrum revealed 9 peaks including six at the group frequency region corresponding to alcohols, carboxylic acid, amine salts, alkenes, alkyne, esters, and oxime functional groups. The ELEC exhibited lower total reducing power (11.06 ±1.34 AAE µg/ml) compared to its total antioxidant capacity (49.26 ±2.44 AAE µg/ml) with a higher (60.47% ±2.44) percentage inhibition of peroxidation than AA (37.98% ±1.88). Furthermore, the ELEC exhibited a lower (0.20 ±0.01 nmol/ml) MDA concentration than AA (0.42 ±0.02 nmol/ml). Conclusively, C. olitorius might be applied for the management of oxidative stress-linked ailments and a source of novel therapeutics for these ailments.

Preparation of Poly (N-Isopropylacrylamide) -Poly (2-Ethyl-2-Oxazoline) and Their Self-Assembly Properties with Dicarboxylic Acid

This study reports the synthesis of copolymers that contain thermally responsive polymers, namely poly(N-isopropylacrylamide) (PNIPAM) and poly(2-ethyl-2-oxazoline) (PEOX), as well as biodegradable side groups that are water-soluble and capable of hydrogen bonding. The assay aims to produce heat-responsive PNIPAM and PEOX polymers with di-carboxylic acid (DCA) controlled structuring of the resulting pH-sensitive nano-structured polymers. These will be used as a template in the synthesis of inorganic materials. The study demonstrated the impact of pH, salt concentration, and temperature on the polymer/DCA. This fragment describes the functional groups of the thermosensitive polymers PNIPAM and PEOX. These polymers have carboxylic acid functional groups at both ends, are water soluble, and are capable of hydrogen bonding. The structure of these polymers can be recognized with small molecules of DCA in an aqueous solution at different pH, salt concentrations, and temperatures with H-bonds. Additionally, these polymers can be used as templates to synthesize hollow silica polymers. The synthesized monomers and polymers were structurally characterized using Fourier transform infrared spectrophotometer (FT-IR). The resulting structured polymers were identified by scanning electron microscopy and atomic force microscopy (SEM, AFM). UV-VIS spectrophotometer and Differential Scanning Calorimetry (DSC) were used to determine the Lower Critical Solution temperature of the polymers.

A fixed-charge model of the N-protomer of 4-aminobenzoic acid to facilitate the study of the unimolecular and bimolecular chemistry of its "neutral" carboxylic acid group.

There are a growing number of examples of protomers formed via electrospray ionization (ESI) that do not fragment under mobile proton conditions, giving rise to distinct tandem mass spectra. To model the N-protomer of 4-aminobenzoic acid, here we study the gas-phase unimolecular and bimolecular chemistry of the 4-(carboxyphenyl)trimethylammonium ion. 4-(Carboxyphenyl)trimethylammonium iodide was synthesized, purified via recrystallization and transferred to the gas phase via ESI. 4-(Carboxyphenyl)trimethylammonium ion, 7, was mass selected and subjected to collision-induced dissociation and ion-molecule reactions in a linear ion trap mass spectrometer. The major fragmentation channel for the fixed-charge cation 7 is methyl radical loss, whereas loss of trimethylamine and CO2 represents minor pathways. The free carboxylic acid functional group of 7 is unreactive toward a number of neutral reagents (methanol, acetone, acetonitrile, and N,N'-diisopropylcarbodiimide). 7 reacts very slowly with trimethylborate via addition-elimination, consistent with density functional theory (DFT) calculations that show this reaction is slightly endothermic. The deuterated cation 7(D) undergoes slow D/H exchange with ethanol, and DFT calculations reveal that a flip-flop mechanism operates. The free carboxylic group of 7 is not very reactive toward neutral reagents in the gas phase.

Stereospecific Indium(III)‐Catalysed Tandem Cycloisomerization of Functionalized 1,6‐enynes: Scope and Mechanistic Insights

AbstractTandem cycloisomerization reactions of functionalized 1,6‐enynes under indium(III) catalysis are described. This atom‐economic transformation proceeds smoothly with 5‐exo‐dig regioselectivity using commercial In(III) halides and 1,6‐enynes furnished with alcohol, carboxylic acid or amine functional groups to give bicyclic structures in good yields and diastereoselectivities. The reaction with enynals involves a three–step mechanism to give an oxatricycle and a conjugated 1,3‐diene. In the absence of the internal nucleophile the enyne cycloisomerization evolves through a skeletal rearrangement or a cyclopropanation reaction after the regioselective 5‐exo‐dig cyclization. The 1,6‐enyne cycloisomerization is stereospecific and the stereoselectivity appears to be independent of the internal nucleophile. Experimental data support a common reaction mechanism involving an initial alkyne electrophilic π‐coordination of In(III) followed by Markovnikov electrophilic alkene addition and ring‐closure by nucleophilic attack. DFT studies hold up a stepwise mechanism involving the formation of a chiral non‐classical carbocation intermediate that determines the diastereoselectivity of this tandem cycloisomerization reaction.

Detection and prebiotic chemistry of possible glycine precursor molecule methylenimine towards the hot molecular core G10.47+0.03

Abstract Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R–NH2) and carboxylic acid (R–COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH2CH2COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH2CH2COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimetre and sub-millimetre wavelengths. We aimed to identify the possible precursors of NH2CH2COOH, because it is highly challenging to identify NH2CH2COOH in the interstellar medium. Many laboratory experiments have suggested that methylenimine (CH2NH) plays a key role as a possible precursor of NH2CH2COOH in the star-formation regions via the Strecker synthesis reaction. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we successfully identified the rotational emission lines of CH2NH towards the hot molecular core G10.47+0.03 using the Atacama Compact Array (ACA). The estimated column density of CH2NH towards G10.47+0.03 is (3.40 ± 0.2) × 1015 cm−2 with a rotational temperature of 218.70 ± 20 K, which is estimated from the rotational diagram. The fractional abundance of CH2NH with respect to H2 towards G10.47+0.03 is 2.61 × 10−8. We found that the derived abundance of CH2NH agree fairly well with the existing two-phase warm-up chemical modelling abundance value of CH2NH. We discuss the possible formation pathways of CH2NH within the context of hot molecular cores, and we find that CH2NH is likely mainly formed via neutral–neutral gas-phase reactions of CH3 and NH radicals towards G10.47+0.03.

Structure and transport properties of self-assembled nanofiltration membranes based on sustainably derived materials

The development of functional polymers using sustainable resources is an increasingly important pursuit. Unsaturated fatty acids represent a potentially interesting class of renewable materials for this purpose. Their unsaturated carbon bonds permit crosslinking to form solid polymers. Additionally, their carboxylic acid functional groups provide for the display of specific surface chemistry within the resulting polymers, and also enable chemical derivatization. Here, we explore the fabrication of nanometer-scale size-selective membranes using conjugated linoleic acid derived monomers. Potassium salt conjugated linoleic acid surfactants (KCLA) self-assembled to form hexagonally packed cylinders (HI) in an aqueous medium containing glycerol. This structure provides a highly ordered medium with aqueous-continuous channels for nanofiltration. The HI mesophase was crosslinked with the addition of bifunctional comonomers and the ordered structure was retained with good fidelity in the resulting thin polymer films (< 400 nm thick). These film function effectively as nanofiltration membranes, with a size cut-off of approximately 1.2 nm for charged solutes, while maintaining a high permeance of ∼ 9 LMH/bar. This performance is on par with several commercial nanofiltration membranes and these materials are therefore of potential interest for advancing sustainability concerns in practical nanofiltration applications.

Analysis of Protein Profile and Functional Groups in Biofilms in the Hypersaline Environment

Halophilic microorganisms include extremophiles that can live and develop in a hypersaline environment. Biofilm, as microecology, consists of a collection of microorganisms attached to a surface, forming an Extracellular Polymeric Substance (EPS) matrix. This study aims to analyze the protein profile and functional groups of biofilms that grow in hypersaline environments. The method used in this study is the SDS PAGE test to diagnose protein profiling and FTIR to analyze biofilm functional groups. The samples used to grow the biofilm came from salt ponds with different NaCl levels, namely 2%, 25%, and 40%. The results showed that each NaCl treatment had different functional groups in the biofilm samples. In the 2% NaCl treatment, there were peaks with solid intensity at the wavenumber 1100 cm-1, indicating the carboxylic acid functional group. In the 25% NaCl treatment, peaks with solid intensity at wavenumber 2250 cm-1 indicate the isocyanate functional group. In the 40% NaCl treatment, there were peaks with solid intensity at wavenumber 860 cm-1, indicating the alkene functional group. The protein analysis for each treatment shows the presence of pyruvate kinase protein in the biofilm with 2% NaCl. The 25% NaCl biofilm sample contained avidin protein, and the 40% NaCl biofilm sample contained tyrosine protein.

Fabrication of silicon quantum dots-methyl viologen nanohybrids: Turn-On-Off-On fluorescence nanoprobe for the detection of d-penicillamine

This study provides a straightforward, one-step hydrothermal approach for synthesizing water-soluble silicon quantum dots (SiQDs). The surface of the synthesized SiQDs is modified by the carboxylic acid functional group (A:SiQDs) after succinic anhydride treatment. The modified A:SiQDs, which emitted blue light fluorescence, showed high stability against photobleaching, thermal stability, and good water solubility. The A:SiQDs are conjugated with methyl viologen (MV2+) to develop a nanohybrid for specific D-Penicillamine (D-PA) detection with an LOD of 8 nM. The suggested sensor was effectively used to analyze D-PA in commercial pharmaceutical formulations using the conventional addition method, and it produced results with good accuracy and precision that were nearly equal to those measured.

A remote atmospheric pressure plasma-assisted textile functionalization process on polymeric scaffolds for bone tissue engineering

When adopting polylactic acid (PLA) nonwoven for bone tissue engineering scaffolds, the inert and hydrophobic nature of PLA leads to poor biocompatibility and osteoconductivity, and limits the efficiency of applying bioceramic coatings, such as hydroxyapatite (HAp), for surface functionalization. To tackle these issues, a remote atmospheric pressure plasma (APP) system using a bespoke Pyrex chamber and acrylic acid monomer was designed and employed to functionalize the PLA via depositing carboxylic acid functional groups onto its surface. The remote APP showed being polymeric textile-suitable with an improved efficiency on not only immobilizing carboxylic acid functional groups on the PLA nonwoven than conventional systems but also the alternate soaking process for HAp deposition. Being compared with the neat PLA, the plasma-functionalized PLA exhibited a more hydrophilic surface (from 130.49 ± 1.28° to 117.40 ± 2.53°) with a 30-day stability (from 117.40 ± 2.53° to 119.40 ± 0.75°) and showed better biocompatibility (136 % to the neat PLA) with MC3T3-E1 mouse embryonic osteoblast cells after HAp deposition. The presence of carboxylic acid functional groups and HAp (Ca/P ratio of 1.7) was also identified using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and a scanning electron microscope with energy dispersive X-ray analysis.

Luminescent properties of multi-stimuli-responsive Ln-BPDC-Phen Lanthanide complexes

Stimuli-responsive smart luminescent materials have attracted more and more attention recently. A series of lanthanide organic complexes, [Ln2(BPDC)3(Phen)2(DMF)2]·5H2O (Ln: lanthanide = Eu, Tb, EuxTb1−x, H2BPDC = 2,2′-Bipyridine-5,5′-dicarboxylic acid, H2Phen = 1,10-phenanthroline, DMF = N,N-dimethylformamide), were synthesized and characterized to be iso-structural. The complexes demonstrate selective and significant response to Fe3+ ions, leading to fast and accurate measuring of Fe3+ ions. Interestingly, the complexes exhibit diverse luminescent response to two isomers 2, 6-pyridine dicarboxylic acid (DPA) and 3, 5-pyridine dicarboxylic acid (H2PDC). The green emission due to Tb3+ ions is enhanced by DPA upon excitation of 280 nm, which is ascribed to the absorption of DPA. Whilst it is quenched by DPA with the excitation of the ligands (339 nm). However, H2PDC quenches both the green and red emissions regardless of the excitation wavelength. The reason is that DPA provides more possibilities of the ligand exchange with the complex due to the suitable position of the carboxylic acid functional groups on the pyridine ring than H2PDC. Simultaneously, the luminescent response of the complex to DPA enables emission color tunability, which allows the complex to recognize and measure DPA/H2PDC isomers visually and easily. Moreover, the complex exhibits a wide-range (110–360 K) temperature sensing with high Sr = 3.92 %K−1 at 180 K. The multi-stimuli-response of the complexes makes them potential applicants for multi-functional sensing materials.

Exploring genetic landscape of low-density polyethylene degradation for sustainable troubleshooting of plastic pollution at landfills

Plastic pollution increases globally due to the high volume of its production and inadequate mismanagement, leading to dumps in landfills affecting terrestrial and aquatic ecosystems. Landfills, as sink for plastics, leach various toxic chemicals and microplastics into the environment. We scrutinized the genetic expression for low-density polyethylene (LDPE) degradation via microorganisms to investigate cell viability and metabolic activities for biodegradation and genetic profiling. Samples were collected from the Pirana waste landfill at Ahmedabad, Gujarat, which is one of the largest and oldest municipal solid waste (MSW) dump sites in Asia. Results analyzed that isolated bacterial culture PN(A)1 (Bacillus cereus) is metabolically active on LDPE as carbon source during starvation conditions when incubated for up to 60 days, which was confirmed via 2,3,5-triphenyl-tetrazolium chloride (TTC) reduction test, reported cell viability and LDPE degradation. Abrasions, surface erosions, and cavity formations were analyzed via scanning electron microscopy (SEM), whereas the breakdown of high molecular polymers converted to low molecules, i.e., depolymerization, was also observed via Fourier-transform infrared (FTIR) spectroscopy over 90 days, along with changes in functional groups of carboxylic acids and aldehyde as well as the formation of polysulfide, aliphatic compounds, aromatic ethers, alcohols, and ether linkages. Further, transcriptomic analysis was performed via DESeq2 analysis to understand key gene expression patterns and pathways involved in LDPE degradation. During the initial phase of LDPE degradation, genes related to biological processes, like membrane transportation, ABC transporters, carbon and lipid metabolism, fatty acid degradation/oxidation, and TCA cycle, are likely to indicate pathways for stress response and molecular functions, like oxidoreductase, catalytic, lyase, transferase, and hydrolase activities were expressed. Interlinking between metabolic pathways indicates biodegradation process that mineralizes LDPE during subsequent incubation days. These pathways can be targeted for increasing the efficiency of LDPE degradation using microbes in future studies. Thus, considering microbial-mediated biodegradation as practical, eco-friendly, and low-cost alternatives, healthy biomes can degrade polymers in natural environments explored by understanding the genetic and enzymatic expression, connecting their role in the process to the likely metabolic pathways involved, thereby increasing the rate of their biodegradation.

Sorption and diffusion of per-polyfluoroalkyl substances (PFAS) in high-density polyethylene geomembranes

The objective of this study is to investigate the fate and transport of per-polyfluoroalkyl substances (PFAS) through a high-density polyethylene (HDPE) geomembrane (GM) that is commonly used in landfill composite liner systems. Tests were conducted to measure the sorption and diffusion of per-polyfluoroalkyl substances (PFAS) with varying number of carbons in chain and functional groups on HDPE GM. Perfluoroalkyl carboxyl acids (PFCAs), perfluoroalkyl sulphonic acids (PFSAs), alkyl-sulfonamidoacetic acids (FOSAAs), fluorotelomer sulfonic acids (FtSAs), alkane sulfonamides (FOSA) and ether carboxylic acids (Gen X) were investigated in this study. The partition coefficients (Kd) on HDPE GM ranged from 3.8 to 98.3 L/kg. PFAS with amide and sulfonic functional groups showed stronger sorption than that of PFAS with carboxylic acid functional groups. Molecular weight directly affected the Kd for long-chained PFAS whereas the Kd of short-chained PFAS was not sensitive to molecular weight. The diffusion coefficients (Dg) of PFCAs and PFSAs through 0.1-mm HDPE GM were found to be in the orders of 10-18 to 10-17 m2/s. The Dg decreased with increasing molar mass and were also observed to be dependent on the functional group. Dg of PFSAs was lower than that of PFCAs for similar number of carbons in the chain. The estimated mass flux for PFAS in an intact 1.5-mm HDPE GM varied from 38.7 to 2080.8 ng/m2/year whereas the estimated diffusive breakthrough time for PFAS in intact 1.5-mm HDPE was 1526 years or longer.