Effect of gradual increase of salt on performance and microbial community during granulation process.

Salinity was considered to have effects on the characteristics, performance microbial communities of aerobic granular sludge. This study investigated granulation process with gradual increase of salt under different gradients. Two identical sequencing batch reactors were operated, while the influent of Ra and Rb was subjected to stepwise increments of NaCl concentrations (0-4 g/L and 0-10 g/L). The presence of filamentous bacteria may contribute to granules formed under lower salinity conditions, potentially leading to granules fragmentation. Excellent removal efficiency achieved in both reactors although there was a small accumulation of nitrite in Rb at later stages. The removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in Ra were 95.31%, 93.70% and 88.66%, while the corresponding removal efficiencies in Rb were 94.19%, 89.79% and 80.74%. Salinity stimulated extracellular polymeric substances (EPS) secretion and enriched EPS producing bacteria to help maintain the integrity and stability of the aerobic granules. Heterotrophic nitrifying bacteria were responsible for NH4+-N and NO2--N oxidation of salinity systems and large number of denitrifying bacteria were detected, which ensure the high removal efficiency of TN in the systems.

Pathways of inhibition of filamentous sludge bulking by slowly biodegradable organic compounds.

The organic compound composition of wastewater, serves as a crucial indicator for the operational performance of activated sludge processes and has a major influence on the development of filamentous bulking in activated sludge. This study focused on the impact of typical soluble and slowly-biodegradable organic compounds, investigating the pathways through which these substrates affect the occurrence of filamentous bulking in systems operated under both high- and low-oxygen conditions. Results showed that slowly-biodegradable organic compounds lead to a concentrated distribution of microorganisms within flocs, with inward growth of filamentous bacteria. Both Tween-80 and granular starch treated systems exhibited a significant increase in protein content. The glucose system, utilizing soluble substrates, exhibited a markedly higher total polysaccharide content. Microbial communities in the Tween-80 and granular starch treated systems were characterized by a higher abundance of bacteria known to enhance sludge flocculation and settling, such as Competibacter, Xanthomonadaceae and Zoogloea. These findings are of high significance for controlling the operational performance and stability of activated sludge systems, deepening our understanding and providing a novel perspective for the improvement of wastewater treatment processes.

Predicting membrane fouling in membrane bioreactor systems using viscosity: Impacts of environmental conditions and antifouling agents.

This study attempted to establish a viscosity-based prediction of membrane fouling. Various factors, including pH, temperature, MLSS concentration, and the addition of NaOCl and citric acid were identified, and their effect on sludge properties such as EPS concentration and wastewater viscosity were estimated. There was a very good correlation between these parameters with EPS concentration and viscosity. The increase in EPS concentration and viscosity significantly affected the membrane flux and filtration time for all the different experimental conditions. However, there were fluctuations in results obtained from experiments related to change in pH, including the addition of antifouling agents NaOCl and citric acid. Such variations accompanied by low correlation in these experiments indicated the influence of pH that may pose difficulty in a viscosity-based estimation of membrane fouling. However, if such large variations in operating conditions could be avoided and the reactor could be operated under optimal conditions, a much better correlation could be obtained between viscosity and membrane fouling. Data from continuously operated MBR systems support this observation, where even a linear equation defining relation between viscosity and transmembrane pressure (TMP) could be obtained. Overall, findings from this study provide a great insight into membrane fouling prediction using viscosity-based methods.

Effects of tire wear particle on growth, extracellular polymeric substance production and oxidation stress of algae Chlorella vulgaris: Performance and mechanism.

Tire wear particles (TWP) represent a distinctive form of microplastics (MPs) that are widely distributed in aquatic ecosystems. However, the toxicity of various types of TWP on phytoplankton remain to be further explored. Thus, three different TWPs originating from replaced bicycle, car, and electro-mobile tire (marked as BTWP, CTWP, and ETWP) were selected and their long-term biological influences on Chlorella vulgaris were investigated. Results demonstrated TWPs showed a concentration-dependent growth promotion of Chlorella vulgaris, with a maximum promotion rate reached to 40.51 % (10 mg/L, 10 d), 23.5 % (80 mg/L, 12 d), and 28.7 % (20 mg/L, 12 d) in the presence of BTWP, CTWP and ETWP, respectively. Meanwhile, TWPs could stimulate the secretion of EPS and induce oxidative stress. EPS analysis revealed the increase of polysaccharides could protect the cell from the direct contact with TWP particles. Moreover, the increased concentration of EPS also helps to induce the settlement of TWP and reduce the leachate release. The release of TWP into the environment could act as an accelerator for the growth of Chlorella vulgaris, which might further change the normal physicochemical behaviors of algae colony in aquatic system. Our findings provide new insights into the toxicity mechanism of TWPs on freshwater algae and valuable data on environmental risk assessment of TWPs.

Algal EPS modifies the toxicity potential of the mixture of polystyrene nanoplastics (PSNPs) and triphenyl phosphate in freshwater microalgae Chlorella sp.

Triphenyl phosphate (TPP) and polystyrene nanoplastics (PSNPs) are prevalent freshwater contaminants obtained mainly from food packaging, textiles and electronics. Algal extracellular polymeric substances (EPS), a part of natural organic matter, may influence these pollutants' behaviour and toxicity. The presence of EPS can enhance the aggregation of TPP-PSNP mixtures, and reduce the bioavailability, and thus the toxicity potential. Understanding the mutual interactions between TPP, PSNPs, and EPS in the aquatic environment is a prerequisite for the environmental risk assessment of these chemicals. The study examines the toxicity effects of various surface-modified PSNPs (1 mg/L of plain, animated, and carboxylated) and TPP (0.05, 0.5, and 5 mg/L) in pristine and combined forms on freshwater microalgae, Chlorella sp., as a model organism. The physical-chemical interactions of algal EPS (10 mg/L) with PSNPs and TPP and their mixtures were studied. The toxicity potential of the PSNPs was estimated by quantifying growth inhibition, oxidative stress, antioxidant activity, and photosynthesis in the cells. TPP toxicity increased in the presence of the PSNPs, however the addition of algal EPS reduced the combined toxic effects. EPS plays a protective role by reducing oxidative stress and enhancing photosynthetic efficiency in the algal cells. The Pearson modeling analysis indicated a positive correlation between growth inhibition, and reactive oxygen species, malondialdehyde production. The cluster heatmap and correlation mapping revealed a strong correlation among the oxidative stress, growth inhibition, and photosynthetic parameters. The study clearly highlights the potential of EPS in mitigating the risk of mixed emerging pollutants in the aquatic environment.

Stimulated C2C12 Myotube Headspace Volatile Organic Compound Analysis.

Understanding exercise metabolism and the relationship with volatile organic compounds (VOCs) holds potential in both health care and sports performance. Exercise metabolism can be investigated using whole body exercise testing (in vivo) or through the culture and subsequent electrical pulse stimulation (EPS) of myotubes (in vitro). This research investigates the novel headspace (HS) analysis of EPS skeletal muscle myotubes. An in vitro system was built to investigate the effect of EPS on the volatile constituents in the HS above EPS skeletal muscle. The C2C12 immortalised cell line was chosen. EPS was applied to the system to induce myotube contraction. The in vitro system was applied to the analysis of VOCs using thermal desorption (TD) sampling. Samples were collected under four conditions: environmental samples (enviro), acellular media HS samples (blank), skeletal muscle myotubes without stimulation HS samples (baseline) and EPS of skeletal muscle myotube HS samples (stim). TD sampling combined with gas-chromatography mass spectrometry (GC-MS) detected two compounds that, after multivariate and univariate statistical analysis, were identified as changing due to EPS (p < 0.05). These compounds were tentatively assigned as 1,4-Dioxane-2,5-dione, 3,6-dimethyl- and 1-pentene. The former is a known lactide and the latter has been reported as a marker of oxidative stress. Further research should focus on improvements to the EPS system, including the use of more relevant cell lines, quantification of myotube contractions, and the application of targeted analysis, metabolic assays and media analysis.

Exopolysaccharide is detrimental for the symbiotic performance of Sinorhizobium fredii HH103 mutants with a truncated lipopolysaccharide core.

The nitrogen-fixing rhizobia-legume symbiosis relies on a complex interchange of molecular signals between the two partners during the whole interaction. On the bacterial side, different surface polysaccharides, such as lipopolysaccharide (LPS) and exopolysaccharide (EPS), might play important roles for the success of the interaction. In a previous work we studied two Sinorhizobium fredii HH103 mutants affected in the rkpK and lpsL genes, which are responsible for the production of glucuronic acid and galacturonic acid, respectively. Both mutants produced an altered LPS, and the rkpK mutant, in addition, lacked EPS. These mutants were differently affected in symbiosis with Glycine max and Vigna unguiculata, with the lpsL mutant showing a stronger impairment than the rkpK mutant. In the present work we have further investigated the LPS structure and the symbiotic abilities of the HH103 lpsL and rkpK mutants. We demonstrate that both strains produce the same LPS, with a truncated core oligosaccharide devoid of uronic acids. We show that the symbiotic performance of the lpsL mutant with Macroptilium atropurpureum and Glycyrrhiza uralensis is worse than that of the rkpK mutant. Introduction of an exoA mutation (which avoids EPS production) in HH103 lpsL improved its symbiotic performance with G. max, M. atropurpureum, and G. uralensis to the level exhibited by HH103 rkpK, suggesting that the presence of EPS might hide the truncated LPS produced by the former mutant.

Biofilm Microenvironment-Sensitive Anti-Virulent and Immunomodulatory Nano-on-Nanodroplets to Combat Refractory Biofilm Infection Through Toxin Neutralization and Phagocytosis.

Biofilm-associated wound infection is principally perceived as the bacterial defense mechanism that hinders antibiotic penetration, causes toxin impairment, and suppresses the immunological responses of the host immune system. Several antibiofilm agents have been developed, but the least of these agents can simultaneously cornerstone on the biofilm-associated immunosuppression and bacterial toxin-induced cellular dysfunction. Inspired by the fusogenic property of nanodroplets and immunomodulatory functions of metal nanoparticles, biofilm targeted anti-virulent immunomodulatory cationic nanoparticle shelled nanodroplets (C-AgND) is fabricated to completely disintegrate and eradicate the Staphylococcus aureus (S. aureus) biofilm. The specific binding of C-AgND neutralizes the negatively charged EPS layer, causing their destabilization followed by penetration of the nanoformulation into the biofilm matrix, killing the persister cells. Consequently, C-AgND eliminates the virulence property of the S. aureus biofilm through α-hemolysin neutralization. C-AgND promotes a strong immunomodulatory effect by polarizing macrophages into their M1 phenotype to induce phagocytosis of the disintegrated biofilm-released residual cells, rejuvenating the host's innate immune responses for the complete eradication of the biofilm. Moreover, the ex vivo skin wound infection model illustrates an excellent biofilm eradication efficacy of C-AgND in comparison to the commercial ones, rendering them to be a promising replacement of existing antibiofilm agents in clinical application.

Remediation of Cd-As-Ni co-contaminated soil by extracellular polymeric substances from Bacillus subtilis: Dynamic improvements of soil properties and ecotoxicity.

As the primary reservoir of heavy metals in nature, soil is highly susceptible to significant co-contamination with Cd-As-Ni. In current study, extracellular polymeric substances (EPS) from Bacillus subtilis were utilized as a novel improver to simultaneously enhance soil property and restrain ecotoxicity in Cd-As-Ni co-contaminated soil. Our findings revealed that EPS effectively bound and immobilized free Cd, As, and Ni in soil and decreased 49.73 % of soil available Cd, 79.16 % of As and 77.87 % of Ni contents by increasing soil pH, soil organic matter and cation exchange capacity. The EPS was also found to inhibit the Cd-As-Ni induced ecotoxicity in Caenorhabditis elegans by increasing the activities of antioxidant enzymes including superoxide dismutase, glutathione, and catalase. The remediation of EPS showed progressive improvement over time, and maintained a lasting effect after achieving peak efficiency. Our results might provide a new perspective on the potential of EPS in remediation of soil heavy metal pollution and the development and utilization of microbial biomass resources in a wider range.

Identification and characterisation of dextran produced by a novel high yielding Weissella cibaria Fiplydextran strain.

An exopolysaccharide (EPS)-producing bacterial strain was isolated from fermented soy milk and identified as Weissella cibaria strain Fiplydextran through morphological, biochemical and 16S rDNA sequence analysis. Here, we report the optimisation of cultural conditions for the organism to achieve maximum EPS production, along with its molecular characterisation, functional properties, and prebiotic potential. The exceptionally high EPS yield (0.61 g per g of sucrose) was obtained from the optimised medium (200 g/L of sucrose, 15 g/L of yeast extract) at 30 °C after 48 h. HPAEC-PAD analysis revealed that the EPS is homopolymer of glucose having Mw as 3.23 × 107 Da determined using viscosity method. Methylation analysis and NMR results confirmed the EPS as dextran with α (1 → 6)-linkage (96.5 %) as main chain and α (1 → 3)- as branch chain linkage (3.5 %). Thermogravimetric analysis exhibited higher thermal stability of EPS. The EPS was observed to support the growth of Bacteroides spp. in pure culture form but not that of Lactobacillus or Bifidobacterium spp. However, a low level of bifidogenic activity was observed upon use of mixed culture of B. fragilis and B. longum. The research implies industrial applications of W. cibaria Fiplydextran for the production of high molecular weight dextran with better yield.

Surface-Adhered Microbubbles Enhance the Resistance of ANAMMOX Granular Sludge to Sulfamethoxazole Stress.

The granule-based anammox process has been reported to be more resistant to the stress of antibiotics; however, the underlying resistance mechanism is still not fully understood. In this study, we found that more microbubbles stably adhered to the surface layer of anammox granular sludge (AnGS, Gs) operating under long-term sulfamethoxazole (SMZ) stress of 2 mg/L, compared to that in the control reactor (Gc). The difference in covering content can be up to over three times (1.0 ± 0.1% vs 0.3 ± 0.0%). Batch tests showed that the coverage ratio of microbubbles on Gs reached approximately 32.5%, which significantly reduced SMZ transfer into AnGS due to the adsorption of SMZ by bubbles, thus alleviating the inhibition of anammox bacterial activity by 36.5%. The adhesion force between the microbubbles and the surface layer of Gs was found to be largely enhanced by 75.0% compared to that of Gc. The increased hydrophobicity of surface layer due to the increased extracellular polymer substance (EPS, mainly proteins) content, and the larger capillary force of surface layer, owing to the unique micronano structure, were identified as key factors responsible for the stable adhesion of microbubbles on the Gs. Consequently, this study demonstrated the vital roles of the surface-adhered microbubbles in resisting the stress of SMZ and shed light on the regulation and development of robust granule-based anammox processes.

Antibacterial and antibiofilm activities of bacteriocin produced by a new strain of Enterococcus faecalis BDR22.

A large number of recalcitrant bacterial pathogens cannot be easily treated by antibiotics due to the existence of biofilm. Hence, an alternative strategy needs to be adopted to remove the biofilm without the development of antibiotic resistance. Bacteriocins, ribosome-mediated proteinaceous toxins, having potential to inhibit the growth of closely or distantly related bacteria. In the present study, after screening a number of sources, a bacteriocin-producing strain, Enterococcus faecalis BDR22, was isolated that showed a significant reduction in the growth of planktonic cells of Gram-positive Staphylococcus aureus, Bacillus subtilis, and Gram-negative Pseudomonas aeruginosa, Escherichia coli, Serratia marcescens, Enterobacter cloacae, and Klebsiella pneumoniae compared to the conventional antibiotic tetracycline. The considerable reduction of the biofilm-forming sessile cells of the test organisms S. aureus (ATCC 23235) and P. aeruginosa (ATCC 10145), with no significant cell revival even after withdrawal of the treatment, was also observed. The extracellular polymeric substance (EPS) content of the biofilm was also reduced, with around 84% total carbohydrate reduction found for both microorganisms. The antibiofilm activities of the strain against test organisms were clearly visible from scanning electron micrographs and confirmed by the changes in functional groups (C-H, -OH, C = C, C-N etc.) of biofilm matrices by Fourier transform infrared spectroscopy (FTIR) analysis. The molecular docking interactions with docking energies ∆G of - 54.40 kcal/mol and - 66.2373 kcal/mol validate the affinity of the bacteriocin towards the biofilm-forming protein, which confirms the competence of the bacteriocin-producing strain to act as an effective antimicrobial and antibiofilm agent, replacing antibiotics.

Shuanghuanglian volatile oil exerts antipyretic, anti-inflammatory, and antibacterial synergistic effects through multiple pathways.

ETHNOPHARMACOLOGICAL RELEVANCE: Traditional Chinese Medicine (TCM) has a rich history spanning 2000 years. Shuanghuanglian, a traditional Chinese herbal formula composed of three botanicals, is primarily used to treat colds, respiratory infections (including bacterial pneumonia), and pharyngitis. Previous research has found that the volatile oil of Shuanghuanglian is crucial for its efficacy. However, there is a lack of studies investigating its mechanisms. AIM OF THE STUDY: This study aims to explore the antibacterial and anti-inflammatory mechanisms of Shuanghuanglian volatile oil and its potential to enhance the antibacterial effects when used in conjunction with antibiotics. METHODS: Determination of the GC-MS fingerprint of SVO using Gas Chromatography-Mass Spectrometry (GC-MS), The antibacterial effects of SVO on multidrug-resistant Klebsiella pneumoniae (MDR-KP) were assessed by detecting MIC, checkerboard method assay, time-kill curves, resistance growth curves, transcriptome sequencing analysis, scanning electron microscopy(SEM), purification, and quantitative analysis of extracellular polysaccharides(EPS). In vivo part, an MDR-KP induced mouse pneumonia model was established to evaluate the mitigating effects of SVO on mouse pneumonia, using comprehensive network pharmacology and bioinformatics to identify genes related to bacterial pneumonia and potential targets of SVO. Validation was performed through molecular docking, qPCR, and ELISA tests. RESULTS: SVO modulates the expression of MDR-KP mRNA for wecB, wecC, murA, murD, murE, murF, inhibiting the synthesis of O-antigen polysaccharides and peptidoglycans, thereby compromising bacterial cell wall integrity and affecting the synthesis of biofilms. These actions not only exhibit antibacterial effects but also enhance antibacterial activity, restoring the sensitivity of CEF to MDR-KP. SVO suppresses the biological activity of PTGS2, reducing the production of Prostaglandin E2 (PGE2), thereby exerting antipyretic and anti-inflammatory effects, providing new insights for the development of natural non-steroidal anti-inflammatory drugs (NSAIDs). CONCLUSIONS: Our research indicates that SVO exerts antipyretic, anti-inflammatory, and antibacterial synergistic effects through multiple pathways.

EbsA is essential for both motility and biofilm formation in the filamentous cyanobacterium Nostoc punctiforme.

Many cyanobacteria, both unicellular and filamentous, exhibit surface motility driven by type IV pili (T4P). While the component parts of the T4P machinery described in other prokaryotes are largely conserved in cyanobacteria, there are also several T4P proteins that appear to be unique to this phylum. One recently discovered component is EbsA, which has been characterized in two unicellular cyanobacteria. EbsA was found to form a complex with other T4P proteins and is essential for motility. Additionally, deletion of ebsA in one of these strains promoted the formation of biofilms. To expand the understanding of ebsA in cyanobacteria, its role in motility and biofilm formation were investigated in the model filamentous cyanobacterium Nostoc punctiforme. Expression of ebsA was strictly limited to hormogonia, the motile filaments of N. punctiforme. Deletion of ebsA did not affect hormogonium development but resulted in the loss of motility and the failure to accumulate surface pili or produce hormogonium polysaccharide (HPS), consistent with pervious observations in unicellular cyanobacteria. Protein-protein interaction studies indicated that EbsA directly interacts with PilB, and the localization of EbsA-GFP resembled that previously shown for both PilB and Hfq. Collectively, these results support the hypothesis that EbsA forms a complex along with PilB and Hfq that is essential for T4P extension. In contrast, rather than enhancing biofilm formation, deletion of both ebsA and pilB abolish biofilm formation in N. punctiforme, implying that distinct modalities for the relationship between motility, T4P function and biofilm formation may exist in different cyanobacteria.

Response surface methodology-based optimization of Inonotus hispidus' liquid fermentation medium and evaluation of its exopolysaccharide activities.

Introduction: Inonotus hispidus, commonly referred to as the Sanghuang mushroom, is a species that is consumed as a tea. To date, this is the only species of the same fungus that has been successfully cultivated. Methods: A single-factor test was conducted using Inonotus hispidus MS-5 and MS-9 as test materials. The response surface methodology was adopted to design and optimise the liquid fermentation medium for them. Results: As indicated in the results, the optimum fermentation conditions for MS-5 include 24.09 g/L glucose, 7.88 g/L yeast extract, 0.99 g/L dandelion powder, 1.5 g MgSO4, 2 g KH2PO4, 0.01 g vitamin B1, and 1 L deionized water; the optimum fermentation conditions for MS-9 include 24.64 g/L glucose, 7.77 g/L yeast extract, 0.98 g/L dandelion powder, 1.5 g MgSO4, 2 g KH2PO4, 0.01 g vitamin B1, and 1 L deionized water. Under such conditions, the mycelial biomass (dry weight) values were able to reach 16.02 g/L and 14.91 g/L for MS-5 and MS-9, respectively, which were 1.6 and 1.54 times those measured before optimization. Discussion: As revealed in the antioxidant and anticancer experiment, Inonotus hispidus exopolysaccharides has corresponding functional effects at the cellular level. This research optimised the liquid culture formulation of Inonotus hispidus and demonstrated that the function of it as a traditional Sanghuang herbal tea is well-documented.

Chemical modification of bacterial exopolysaccharides: Antioxidant properties and health potentials.

In recent years, there has been a burgeoning interest in the utilization of microbial exopolysaccharides (EPS) because of the added advantage of their renewable, biocompatible, and biodegradable nature in addition to intended applications. The endowed properties of bacterial EPS make them valuable candidates for a wide array of industrial applications. Modification of native EPS is known to enhance various physico-chemical and functional properties. Various modifications such as physical, chemical, biological, and enzymatic modifications were practiced improving the bioactivity of EPS. This paper comprehensively aims to review the most recent chemical modification techniques employed to modify the physico-chemical and functional changes of bacterial EPS in comparison with the unmodified forms. Chemical modification entails strategic alterations to the structure and properties of EPS through various synthetic and semi-synthetic methodologies. Emphasis is given to the antioxidant potential and functional role of these EPS derivatives in human health. Antioxidant properties reveal a significant augmentation in activity compared to their native counterparts. Such enhancement holds a strong promise for potential benefits and therapeutic applications. Chemical derivatives of EPS with overwhelming functional benefits could surely encourage EPS application, particularly as potential hydrocolloids in industrial and biomedical contexts.

Effectiveness of Vitamin E in Treatment of Antipsychotic-Induced Tardive Dyskinesia and Extrapyramidal Symptoms: A Case Report.

Antipsychotic medications, while crucial in managing severe psychiatric disorders such as schizophrenia and bipolar disorder, are frequently associated with extrapyramidal symptoms (EPS) and tardive dyskinesia (TD). TD, characterized by repetitive, involuntary movements, especially of the face and limbs, poses a substantial clinical challenge due to its often irreversible nature. Conventional management strategies, including dose reduction and switching to atypical antipsychotics, frequently offer limited success, prompting exploration of alternative therapies. This case report highlights the effectiveness of vitamin E, a potent antioxidant, in treating a 28-year-old male with severe antipsychotic-induced EPS and TD, unresponsive to traditional therapies. The patient, who had been receiving paliperidone injections as part of his psychotic disorder treatment regimen, developed marked EPS, including muscle rigidity, a parkinsonian gait, significant motor disturbances as well as tardive dyskinesia. Despite discontinuation of paliperidone and initiation of procyclidine, propranolol, clonazepam, and omega-3 supplements, his symptoms persisted. Introduction of oral vitamin E at 400 IU daily led to a dramatic improvement, with an 80% reduction in EPS and TD symptoms within weeks. The patient's Abnormal Involuntary Movement Scale (AIMS) score decreased from 24 to 4, and his overall quality of life improved significantly. Gradual increase of vitamin E dosage to 1200 IU daily, coupled with tapering of other medications, eventually led to complete resolution of symptoms, as evidenced by an AIMS score of 0. The patient maintained symptom-free status during follow-up, with no recurrence of psychotic symptoms. This case underscores the potential role of vitamin E as a viable adjunctive treatment for TD, particularly in patients who do not respond adequately to conventional therapies. While the literature presents mixed evidence regarding vitamin E's effectiveness, this case adds to the growing body of research suggesting its benefits, especially when introduced early in the disease course. Further large-scale studies are warranted to establish the most effective treatment protocols and identify patient populations most likely to benefit from vitamin E therapy.

Response of aerobic granular sludge to salinity fluctuations in formation, stability and microbial community structures.

Aerobic granular sludge (AGS) exhibits excellent resistance to adverse environment due to its unique layered structure. However, the mechanism about how salinity fluctuations in municipal wastewater impact AGS formation and its physicochemical properties has not been thoroughly revealed. In this study, AGS was cultivated under additional 0 % salinity (R1), additional 1.5 % constant salinity (R2), and additional 0-1.5 % fluctuant salinity (R3), respectively. The results indicate that increased salinity can enhance extracellular polymeric substances (EPS) production and improve sludge settleability, thereby facilitate AGS formation. However, the AGS experienced frequent environmental conversion between dehydration and swell due to salinity fluctuations, resulting in higher content of loosely-bond EPS and low settleability, which delayed the maturation of AGS for over 14 days. Additional salinity significantly inhibited the nitrification process, but the formation of AGS promoted the recovery of ammonia oxidation activity and facilitated the construction of short-range nitrification denitrification processes, resulting in over 16.0 % higher total nitrogen removal efficiency than R1. The microbial community analysis revealed that Thauera played an important role in the granulation process under salinity stress, due to its salt tolerance and EPS secretion abilities. As expected, the formation of AGS enhanced the salt resistance of microorganisms, allowing for the enrichment of functional bacteria, such as Flavobacterium and Candidatus_Competibacter. Generally, microorganisms required extended adaptation periods to cope with salinity fluctuations. Nevertheless, the resulting AGS proved stable and efficient wastewater treatment performance.

Impact of weathered and virgin polyethylene terephthalate (PET) micro- and nanoplastics on growth dynamics and the production of extracellular polymeric substances (EPS) of microalgae.

The ever-increasing plastic waste accumulation in the marine environment necessitates a deeper understanding of microalgae interactions with micro- and nanoplastics (MNP), and the role of extracellular polymeric substances (EPS). EPS, known for its adhesive properties and produced as an algal stress response, may facilitate aggregation of both algae and MNPs, thereby impacting ecological and hydrodynamic processes such as the trophic transfer or vertical transport of MNPs. Moreover, gaining a deeper understanding of the impact of weathering processes on the potential toxicological effects of plastic particles, and the comparative significance of plastic-specific effects relative to those of naturally occurring particles such as kaolin clay, is imperative. Therefore, this study investigated the impact of fragmented, polydisperse virgin polyethylene terephthalate (PET, Daverage = 910 nm) and weathered PET (Daverage = 1700 nm) on the growth and the production of EPS of Rhodomonas salina. Algae were exposed to a range of low MNP concentrations (10, 100 and 1000 and 10,000 MNPs ml-1) for 11 days. A natural particle control (kaolin, Daverage = 1600 nm) was deployed to differentiate particle effects from plastic effects. It was observed that exposure to both weathered PET and virgin PET resulted in initially increased growth rates (7.80 % and 7.28 % respectively), followed by significant decreases in algae cell density (-30.1 % and -11.2 % respectively). Furthermore, exposure to weathered PET caused a simultaneous elevation in cellular EPS production (76.51 %). The effects of plastics were significantly larger than the effect of kaolin. Also, the observed effects were amplified by the weathering of the plastics. These observations underscore the interactions between particle type, age and concentration, and their distinct impacts on algae density and growth inhibition. The observations indicate a role for EPS as an algal protection mechanism, potentially affecting the environmental fate of MNP - microalgae aggregates.