Anaerobic degradation of alcohol ethoxylates and polyethylene glycols in marine sediments

A Comparative Analysis of Physiological and Morphological Alteration in Mytilus galloprovincialis After Exposure to Polyethylene Glycol (PEG)

This study investigates the effects of polyethylene glycol (PEG) on Mytilus galloprovincialis, a key sentinel species in marine environments. As PEGs are widely used in personal care products and pharmaceuticals, their increasing presence in marine ecosystems poses a potential threat to non-target organisms. A total of 150 mussels were exposed to different concentrations of PEG (0.1 mg/L and 10 mg/L) over 14 days. The impact of PEG exposure was assessed through cell viability assays, regulatory volume decrease (RVD) tests, and histological analysis, respectively, on hemolymph and digestive gland (DG) cells, on gills, DG, and gonads. Significant reductions in cell viability were observed in hemocytes and DG cells, particularly at higher PEG concentrations. Histological analysis revealed pronounced tissue damage, including hemocyte infiltration, lipofuscin aggregation, and epithelial disorganization in the gills, hepatopancreas, and gonads, indicating PEG-induced cytotoxicity. The study also observed impaired RVD mechanisms in DG cells, highlighting changes in cell volume regulation. These findings demonstrate that PEG can induce significant physiological and morphological alterations in marine mussels, raising concerns about its impact on aquatic ecosystems.

Exploring micropollutants in polar environments based on non-target analysis using LC-HRMS

The routine use of chemicals in polar regions contributes to unexpected occurrence of micropollutants, with sewage discharge as a prominent pollution source. The aim of this study was to identify and quantify micropollutants in polar environments near potential point sources using non-target analysis (NTA) with liquid chromatography high-resolution mass spectrometry. Seawater samples were collected from Ny-Ålesund, Svalbard and Marian Cove, King George Island, in 2023. We tentatively identified 32 compounds with NTA, along with 105 homologous series substances. Of these, 18 substances were confirmed, and 13 were quantified using the internal standard method. Most quantified substances in the Ny-Ålesund, including caffeine, naproxen, and polyethylene glycols (PEGs), exhibited concentrations ranged from 0.9 to 770,000 ng/L. In Marian Cove, the analysis predominantly detected acetaminophen, with concentrations ranging from 13 to 35 ng/L. The findings underscore the presence and spatial distribution of emerging micropollutants resulting from wastewater discharge in polar regions.

From Personal Care to Coastal Concerns: Investigating Polyethylene Glycol Impact on Mussel's Antioxidant, Physiological, and Cellular Responses

Pharmaceutical and personal care products (PPCPs) containing persistent and potentially hazardous substances have garnered attention for their ubiquitous presence in natural environments. This study investigated the impact of polyethylene glycol (PEG), a common PPCP component, on Mytilus galloprovincialis. Mussels were subjected to two PEG concentrations (E1: 0.1 mg/L and E2: 10 mg/L) over 14 days. Oxidative stress markers in both gills and digestive glands were evaluated; cytotoxicity assays were performed on haemolymph and digestive gland cells. Additionally, cell volume regulation (RVD assay) was investigated to assess physiological PEG-induced alterations. In the gills, PEG reduced superoxide dismutase (SOD) activity and increased lipid peroxidation (LPO) at E1. In the digestive gland, only LPO was influenced, while SOD activity and oxidatively modified proteins (OMPs) were unaltered. A significant decrease in cell viability was observed, particularly at E2. Additionally, the RVD assay revealed disruptions in the cells subjected to E2. These findings underscore the effects of PEG exposure on M. galloprovincialis. They are open to further investigations to clarify the environmental implications of PPCPs and the possibility of exploring safer alternatives.

Water-Soluble Synthetic Polymers: Their Environmental Emission Relevant Usage, Transport and Transformation, Persistence, and Toxicity

Water-soluble synthetic polymers (WSPs) are distinct from insoluble plastic particles, which are both critical components of synthetic polymers. In the history of human-made macromolecules, WSPs have consistently portrayed a crucial role and served as the ingredients of a variety of products (e.g., flocculants, thickeners, solubilizers, surfactants, etc.) commonly used in human society. However, the environmental exposures and risks of WSPs with different functions remain poorly understood. This paper provides a critical review of the usage, environmental fate, environmental persistence, and biological consequences of multiple types of WSPs in commercial and industrial production. Investigations have identified a wide market of applications and potential environmental threats of various types of WSPs, but we still lack the suitable assessment tools. The effects of physicochemical properties and environmental factors on the environmental distribution as well as the transport and transformation of WSPs are further summarized. Evidence regarding the degradation of WSPs, including mechanical, thermal, hydrolytic, photoinduced, and biological degradation is summarized, and their environmental persistence is discussed. The toxicity data show that some WSPs can cause adverse effects on aquatic species and microbial communities through intrinsic toxicity and physical hazards. This review may serve as a guide for environmental risk assessment to help develop a sustainable path for WSP management.

Characterization of water-soluble synthetic polymeric substances in wastewater using LC-HRMS/MS

Synthetic water-soluble polymeric materials are widely employed in e.g. cleaning detergents, personal care products, paints or textiles. Accordingly, these compounds reach sewage treatment plants and may enter receiving waters and the aquatic environment. Characteristically, these molecules show a polydisperse molecular weight distribution, comprising multiple repeating units, i.e. a homologous series (HS). Their analysis in environmentally relevant samples has received some attention over the last two decades, however, the majority of previous studies focused on surfactants and a molecular weight range <1000 Da. To capture a wider range on the mass versus polarity plane and extend towards less polar contaminants, a workflow was established using three different ionization strategies, namely conventional electrospray ionization, atmospheric pressure photoionization and atmospheric pressure chemical ionization. The data evaluation consisted of suspect screening of ca. 1200 suspect entries and a non-target screening of HS with pre-defined accurate mass differences using ca. 400 molecular formulas of repeating units of HS as input and repeating retention time shifts as HS indicator. To study the fate of these water-soluble polymeric substances in the wastewater treatment process, the different stages, i.e. after primary and secondary clarifier, and after ozonation followed by sand filtration, were sampled at a Swiss wastewater treatment plant. Remaining with two different ionization interfaces, ESI and APPI, in both polarities, a non-targeted screening approach led to a total number of 146 HS (each with a minimum number of 4 members), with a molecular mass of up to 1200 detected in the final effluent. Of the 146 HS, ca 15% could be associated with suspect hits and approximately 25% with transformation products of suspects. Tentative characterization or probable chemical structure could be assigned to almost half of the findings. In positive ionization mode various sugar derivatives with differing side chains, for negative mode structures with sulfonic acids, could be characterized. The number of detected HS decreased significantly over the three treatment stages. For HS detectable also in the biological and oxidative treatment stages, a change in HS distribution towards to lower mass range was often observed.

How to accurately assess surfactant biodegradation-impact of sorption on the validity of results

Surfactants not only are widely used in biotechnological processes but also constitute significant contaminants of the modern world. Among many reports, there is a shortage of works which summarize the issue of surfactant sorption to biomass in a way that would elucidate the biological factors for analysts and analytical factors for microbiologists. The main factor, which is not as obvious as one would expect, is associated with the susceptibility of analytical approaches to errors resulting from incorrect handling of biomass. In case of several publications reviewed in the framework of this study, it was not possible to establish whether the decrease of the analytical signal observed by the authors actually resulted from biodegradation of the surfactant. This review emphasizes the necessity to consider the possibility of surfactant sorption to microbial cells, which may result in significant detection errors as well as conceptual inconsistency. In addition, a reference study regarding representative surfactants (cationic, anionic and non-ionic) as well as yeast, Gram-negative, Gram-positive bacteria, and activated sludge was provided to highlight the possible errors which may arise from disregarding sorption processes when determining degradation of surfactants. This particularly applies to systems which include ionic surfactants and activated sludge as sorption may account for 90% of the observed depletion of the surfactant. Therefore, a systematic approach was proposed in order to improve the credibility of the obtained results. Finally, the need to employ additional procedures was highlighted which may be required in order to verify that the decrease of surfactant concentration results from biodegradation processes.

Regulating acidogenesis and methanogenesis for the separated bio-generation of hydrogen and methane from saline-to-hypersaline industrial wastewater

Given the limitations of acidogens and methanogens activities under saline environments, this work aims to optimize the main operational parameters affecting hydrogen and methane production from saline-to-hypersaline wastewater containing mono-ethylene glycol (MEG). MEG is the main contaminant in several saline industrial effluents. Anaerobic baffled reactor (ABR), as a multi-stage system, was used at different temperatures (i.e., 19-31 °C [ambient] and 35 °C), organic loading rates (OLRs) of 0.6-2.2 gCOD/L/d, and salinity of 5-35 gNaCl/L. Mesophilic conditions of 35 °C substantially promoted MEG biodegradability (92-98%) and hydrogen/methane productivity, even at elevated salinity. Hydrogen yield (HY) and methane yield (MY) peaked to 258 and 140 mL/gCOD_add, respectively, at OLR 0.64 gCOD/L/d and salinity up to 20-25 gNaCl/L. An immobilized sludge ABR (ISABR), packed with polyurethane media, was further compared with classical ABR, resulting in 1.8-fold higher MY, at 35 gNaCl/L. Microbial analysis showed that introducing attached growth system (ISABR) substantially promoted methanogens abundance, which was dominated by genus Methanosarcina. Among bacterial genera, Acetobacterium was dominant, particularly in 1^st compartment, representing MEG-degrading/salt-tolerant genus. At high salinity up to 35 gNaCl/L, the multi-phase and attached growth configuration can efficiently reduce the induced salt stress, particularly on methanogens, towards balanced and separated acidogenesis/methanogenesis. Overall, producing hydrogen and methane from anaerobic treatment of MEG-based saline wastewater is feasible at optimized parameters and configuration.

Biostimulants application for bacterial metabolic activity promotion and sodium dodecyl sulfate degradation under copper stress

In this study, the metabolic activity (adenosine triphosphate, ATP; electron transfer system, ETS; and dehydrogenase activity, DHA) response of a sodium dodecyl sulfate (SDS) degrading bacterium Pseudomonas sp. SDS-N2 to copper stress conditions were investigated. Results showed that the ATP content, ETS activity, and DHA activity of strain SDS-N2 were significantly correlated with substrate removal efficiency and bacterial growth under copper stress conditions. Based on the metabolic response patterns of strain SDS-N2, biostimulants citric acid, proline as well as FeSO₄ were used to promote the metabolic activity of strain SDS-N2 at 0.8 mg L^-1 copper stress condition. Plackett-Burman design and analysis proved that citric acid and FeSO₄ were significant factors for enhanced SDS removal; and the optimum biostimulation conditions (FeSO₄ 72 mg L^-1 and citric acid 100 mg L^-1) for SDS removal were obtained by using steepest ascent experiment and central composite design. Under the optimum biostimulation conditions, ATP, ETS, DHA activity as well as bacterial growth were 14.1, 45.5, 0.5 and 2.3-fold higher than that of the control (without FeSO₄ and citric acid addition) after 12.5 h biodegradation, and the substrate removal efficiency was increase by 37.6%.

Sub-lethal toxicity of chlorpyrifos alone and in combination with polyethylene glycol to common carp (Cyprinus carpio)

In the present study, sub-lethal effects of chlorpyrifos, alone (25 and 50 μg L^-1) and in combination with Polyethylene glycol (5 and 10 mg L^-1), on common carp were investigated. Exposure to chlorpyrifos caused significant changes in all blood biochemical parameters compared to control groups. Total protein, triglyceride, glucose levels, as well as lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), and creatine phosphokinase (CPK) activities in plasma changed after exposure to 10 mg L^-1 polyethylene glycol (PEG), while fish exposed to PEG did not show any significant difference in aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and acetylcholinesterase (AChE) activities and albumin and globulins levels. Exposure to a combination of chlorpyrifos and PEG caused a significant change in AST, GGT, CPK, LDH and AChE activity, total protein and glucose level. The influence of chlorpyrifos and PEG combination on ALP, cholesterol, triglyceride, albumin, and globulin depends on the concentration of the insecticide and PEG. With a reduction in chlorpyrifos concentration, PEG can maintain ALP activity and albumin at a normal level. Although fish exposure to chlorpyrifos, alone or in combination with polyethylene glycol, significantly increased malondialdehyde (MDA) and catalase (CAT) level, it decreased total antioxidant level (TAN). Exposure to just polyethylene glycol had no impact on CAT activity, TAN and MDA level. According to the results, PEG can have an antagonistic effect on chlorpyrifos toxicity, depending on these two materials concentration. However, chlorpyrifos increased the toxicity of PEG.

Determination of dodecanol and ethoxylated fatty alcohols from environmental samples using diatomaceous earth as a green sorbent for solid-phase extraction

This study describes the use of diatomaceous earth during solid-phase extraction as an efficient sorbent for separation and concentration of dodecanol and ethoxylated dodecanol containing 1-9 ethoxyl groups. The efficiency of different eluents was evaluated for model samples which allowed to select methanol and chloroform for tests with river water samples. During model experiments, it was observed that the recovery rates of specific compounds in the studied mixture were influenced by the character of the solvent used for desorption. Hydrophobic compounds, such as dodecanol and ethoxylated dodecanol with 1-3 ethoxyl groups, were eluted by chloroform with 100% efficiency. In case of the remaining compounds, which were more hydrophilic, a 97% recovery rate was achieved during elution with methanol. Such dependencies were not observed in case of river water samples, as the results obtained for both studied sorbent-eluent systems were comparable. In both variants the recovery of dodecanol and ethoxylated dodecanol containing 1-9 ethoxyl groups ranged from 33 to 99%.

Anaerobic degradation of glycol ether-ethanol mixtures using EGSB and hybrid reactors: Performance comparison and ether cleavage pathway

The anaerobic biodegradation of ethanol-glycol ether mixtures as 1-ethoxy-2-propanol (E2P) and 1-methoxy-2-propanol (M2P), widely used in printing facilities, was investigated by means of two laboratory-scale anaerobic bioreactors at 25^oC: an expanded granular sludge bed (EGSB) reactor and an anaerobic hybrid reactor (AHR), which incorporated a packed bed to improve biomass retention. Despite AHR showed almost half of solid leakages compared to EGSB, both reactors obtained practically the same performance for the operating conditions studied with global removal efficiencies (REs) higher than 92% for organic loading rates (OLRs) as high as 54 kg of chemical oxygen demand (COD) m^-3 d^-1 (REs of 70% and 100% for OLRs of 10.6 and 8.3 kg COD m^-3 d^-1 for E2P and M2P, respectively). Identified byproducts allowed clarifying the anaerobic degradation pathways of these glycol ethers. Thus, this study shows that anaerobic scrubber can be a feasible treatment for printing emissions.

Anaerobic biodegradation of (emerging) organic contaminants in the aquatic environment

Although strictly anaerobic conditions prevail in several environmental compartments, up to now, biodegradation studies with emerging organic contaminants (EOCs), such as pharmaceuticals and personal care products, have mainly focused on aerobic conditions. One of the reasons probably is the assumption that the aerobic degradation is more energetically favorable than degradation under strictly anaerobic conditions. Certain aerobically recalcitrant contaminants, however, are biodegraded under strictly anaerobic conditions and little is known about the organisms and enzymatic processes involved in their degradation. This review provides a comprehensive survey of characteristic anaerobic biotransformation reactions for a variety of well-studied, structurally rather simple contaminants (SMOCs) bearing one or a few different functional groups/structural moieties. Furthermore it summarizes anaerobic degradation studies of more complex contaminants with several functional groups (CMCs), in soil, sediment and wastewater treatment. While strictly anaerobic conditions are able to promote the transformation of several aerobically persistent contaminants, the variety of observed reactions is limited, with reductive dehalogenations and the cleavage of ether bonds being the most prevalent. Thus, it becomes clear that the transferability of degradation mechanisms deduced from culture studies of SMOCs to predict the degradation of CMCs, such as EOCs, in environmental matrices is hampered due the more complex chemical structure bearing different functional groups, different environmental conditions (e.g. matrix, redox, pH), the microbial community (e.g. adaptation, competition) and the low concentrations typical for EOCs.

Parallel pathways of ethoxylated alcohol biodegradation under aerobic conditions

Non-ionic surfactants (NS) are a major component of the surfactant flux discharged into surface water, and alcohol ethoxylates (AE) are the major component of this flux. Therefore, biodegradation pathways of AE deserve more thorough investigation. The aim of this work was to investigate the stages of biodegradation of homogeneous oxyethylated dodecanol C12E9 having 9 oxyethylene subunits, under aerobic conditions. Enterobacter strain Z3 bacteria were chosen as biodegrading organisms under conditions with C12E9 as the sole source of organic carbon. Bacterial consortia of river water were used in a parallel test as an inoculum for comparison. The LC-MS technique was used to identify the products of biodegradation. Liquid-liquid extraction with ethyl acetate was selected for the isolation of C12E9 and metabolites from the biodegradation broth. The LC-MS/MS technique operating in the multiple reaction monitoring (MRM) mode was used for quantitative determination of C12E9, C12E8, C12E7 and C12E6. Apart from the substrate, the homologues C12E8, C12E7 and C12E6, being metabolites of C12E9 biodegradation by shortening of the oxyethylene chain, as well as intermediate metabolites having a carboxyl end group in the oxyethylene chain (C12E8COOH, C12E7COOH, C12E6COOH and C12E5COOH), were identified. Poly(ethylene glycols) (E) having 9, 8 and 7 oxyethylene subunits were also identified, indicating parallel central fission of C12E9 and its metabolites. Similar results were obtained with river water as inoculum. It is concluded that AE, under aerobic conditions, are biodegraded via two parallel pathways: by central fission with the formation of PEG, and by Ω-oxidation of the oxyethylene chain with the formation of carboxylated AE and subsequent shortening of the oxyethylene chain by a single unit.

Bacterial strains isolated from river water having the ability to split alcohol ethoxylates by central fission

Alcohol ethoxylates (AE) are a major component of the surfactant stream discharged into surface water. The "central fission" of AE with the formation of poly(ethylene glycols) (PEG) is considered to be the dominant biodegradation pathway. However, information as to which bacterial strains are able to perform this reaction is very limited. The aim of this work was to establish whether such an ability is unique or common, and which bacterial strains are able to split AE used as a sole source of organic carbon. Four bacterial strains were isolated from river water and were identified on the basis of phylogenetic trees as Enterobacter strain Z2, Enterobacter strain Z3, Citrobacter freundii strain Z4, and Stenotrophomonas strain Z5. Sterilized river water and "artificial sewage" were used for augmentation of the isolated bacteria. The test was performed in bottles filled with a mineral salt medium spiked with surfactant C12E10 (10 mg L(-1)) and an inoculating suspension of the investigated bacterial strain. Sequential extraction of the tested samples by ethyl acetate and chloroform was used for separation of PEG from the water matrix. LC-MS was used for PEG determination on the basis of single-ion chromatograms. All four selected and investigated bacterial strains exhibit the ability to split fatty alcohol ethoxylates with the production of PEG, which is evidence that this property is a common one rather than specific to certain bacterial strains. However, this ability increases in the sequence: Stenotrophomonas strain Z5 < Enterobacter strain Z2 < Enterobacter strain Z3 = Citrobacter freundii strain Z4. Graphical Abstract Biodegradation by central fission of alcohol ethoxylates by bacterial strains isolated from river water.