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.

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 facilitating 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.

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.

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.

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.

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.

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.

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.

Sucrose contributed to the biofilm formation of Tetragenococcus halophilus and changed the biofilm structure.

Based on the previous research results that the addition of sucrose in the medium improved the biofilm formation of Tetragenococcus halophilus, the influence of sucrose on biofilm formation was explored. Moreover, the influence of exogenous expression of related genes sacA and galE from T. halophilus on the biofilm formation of L. lactis NZ9000 was investigated. The results showed that the addition of sucrose in the medium improved the biofilm formation, the resistance of biofilm cells to freeze-drying stress, and the contents of exopolysaccharides (EPS) and eDNA in the T. halophilus biofilms. Meanwhile, the addition of sucrose in the medium changed the monosaccharide composition of EPS and increased the proportion of glucose and galactose in the monosaccharide composition. Under 2.5% (m/v) salt stress condition, the expression of gene sacA promoted the biofilm formation and the EPS production of L. lactis NZ9000 with the sucrose addition in the medium and changed the EPS monosaccharide composition. The expression of gene galE up-regulated the proportion of rhamnose, galactose, and arabinose in the monosaccharide composition of EPS, and down-regulated the proportion of glucose and mannose. This study will provide a theoretical basis for regulating the biofilm formation of T. halophilus, and provide a reference for the subsequent research on lactic acid bacteria biofilms.

Isolation and assessment of the beneficial effect of exopolysaccharide-producing PGPR in Triticum aestivum (L.) plants grown under NaCl and Cd -stressed conditions.

Exopolysaccharide (EPS)-producing beneficial bacteria play a multifaceted role in improving plant growth and adaptive responses against different stressors. In this study, we isolated 25 bacterial strains from pea nodules and were further studied for their sodium chloride (NaCl) and cadmium (Cd) stress tolerance. Based on our results, Rhizobium fabae SR-22 (NCBI Accession number: MG063739.1) showed better tolerance toward salinity and Cd stress and produced a wide range of plant growth-promoting compounds. However, the amount of EPS varies during NaCl and Cd stress. It was important to note that NaCl and Cd beyond the tolerant level, affected the morphology and cellular viability of R. fabae. Interestingly, plant growth-promoting (PGP) substances (indole-3-acetic acid, ammonia, siderophore, and ACC deaminase) released by R. fabae were increased with increasing NaCl concentrations. In contrast, PGP substances were greatly decreased by increasing Cd dosages. Further, the beneficial effect of EPS-producing R. fabae in Triticum aestivum grown in soil treated with different levels of NaCl and Cd was assessed. Inoculation of R. fabae in wheat seedlings grown under higher NaCl and Cd concentrations showed improved growth compared to non-inoculated plants. R. fabae exhibited maximum effect in wheat plants grown under 2% NaCl and increased seed germination (8%), root length (13%), vigor indices (19%), root biomass (20%), chlorophyll-a (31%), total chlorophyll (27%) and carotenoid content. Additionally, R. fabae increased Cd and NaCl tolerance in wheat seedlings and improved their antioxidative responses. Conclusively, this work demonstrated that EPS-producing R. fabae showed a promising role in mitigating salinity and Cd-stress in wheat possibly by reducing salt and HM stress-induced abrasions and growth promotion via inorganic phosphate solubilization, and increased nutrient absorption. In the future, R. fabae equipped with these distinguishing characteristics may be used as effective bio-inoculants/bio-formulations in agriculture to address salinity and HM stress issues.

Deciphering the molecular interaction of extracellular polymeric substances of a marine bacterium Pseudomonas furukawaii PPS-19 with petroleum hydrocarbons and development of bioadsorbent.

Petroleum hydrocarbon contamination is a serious hazard to marine environments, affecting ecosystems and marine life. However, extracellular polymeric substances (EPS) of marine bacteria constituting various hydrophilic and hydrophobic functional groups sequester petroleum hydrocarbons (PHs). In this study, interaction of EPS of Pseudomonas furukawaii PPS-19 with PHs such as crude oil, n-dodecane, and pyrene and its impact on PHs adsorption was investigated. Protein component of EPS was increased after treatment with PHs. Red shift of UV-Vis spectra implied change in molecular structure of EPS. Functional groups of proteins (CO, NH2) and polysaccharides (C-C, C-OH, C-O-C) predominantly interacted with PHs. Interaction with PHs affected secondary structure of EPS. Change in binding energies of corresponding functionalities of C 1s, O 1s, and N 1s confirmed the interaction. Disruption of crystalline peaks led to increased pore size in EPS primarily due to the increase in surface electronegativity. Static quenching mechanism unveils formation of complex between fulvic acid of EPS and PHs. Relative expression of alg8 gene was significantly increased in the presence of n-dodecane (6.31 fold) (P < 0.05; One way ANOVA). n-dodecane and pyrene adsorption capacity of Immobilized EPS was significantly higher (356.5 and 338.2 mg g-1, respectively) (P < 0.001; One way ANOVA) than control. Adsorption rate fits into the pseudo-second-order kinetic model. This study establishes that interaction of PHs causes structural and physical changes in EPS and EPS could be used as an adsorbent material for the sequestration of PHs pollution.

Construction nanobiotechnology approach for performance enhancement of microbially induced biomineralization (MIB) using a biopolymer encapsulated spore-based system.

The integration of green construction practices within the built environment has been significantly advanced by biotechnological innovations, among which microbially induced biomineralization (MIB), predominantly facilitated by various strains of spore-forming bacilli, emerges as a pivotal mechanism for the self-healing of concrete. However, the practical deployment of this technology faces challenges, notably the compromised viability of bacterial spores due to germination triggered by severe shear stress during concrete mixing. To address this limitation, a water-insoluble polymer (extracellular polymeric substance) produced by Cellulomonas flavigena was utilized to encapsulate and protect the spores. The encapsulation process was rigorously verified through physicochemical methodologies, including X-ray diffraction (XRD) analysis, which revealed alterations in the interlayer spacings of the extracellular polymeric substance (EPS) structure during the encapsulation process, indicating successful EPS coating of the spores. Furthermore, a proof of concept for the enhanced biomineralization capacity of EPS-coated spores was demonstrated. Standard analytical techniques confirmed the precipitation of calcite and vaterite among other minerals, underscoring the effectiveness of this novel approach. This breakthrough paves the way for the development of innovative, sustainable bioconcrete applications, aligning with broader environmental objectives and advancing the field of green construction technology.IMPORTANCEDevelopment of bioconcrete with self-healing capability through MIB constitutes an important sustainable construction biotechnology approach for restoration and repair of built environment. Like every promising technology, MIB also suffers from certain shortcomings in terms of compromised viability of the microbial cells after premature germination of the spores on exposure to shear stress caused during concrete mixing. In this study, these challenges were adequately addressed by successfully providing a protective coating of indigenously extracted EPS to the bacterial spores and elucidating the interactive mechanisms between them. The results showed stable encapsulation of the spores while providing mechanistic insights of the encapsulation phenomenon. The data also showed enhanced rate of biomineralization by encapsulated microbes when subjected to stress conditions.

UPCARE: Urinary Extracellular Vesicles-Derived Prostate Cancer Assessment for Risk Evaluation.

In the quest for efficient tumor diagnosis via liquid biopsy, extracellular vesicles (EVs) have shown promise as a source of potential biomarkers. This study addresses the gap in biomarker efficacy for predicting clinically significant prostate cancer (csPCa) between the Western and Chinese populations. We developed a urinary extracellular vesicles-based prostate score (EPS) model, utilizing the EXODUS technique for EV isolation from 598 patients and incorporating gene expressions of FOXA1, PCA3, and KLK3. Our findings reveal that the EPS model surpasses prostate-specific antigen (PSA) testing in diagnostic accuracy within a training cohort of 234 patients, achieving an area under the curve (AUC) of 0.730 compared to 0.659 for PSA (p = 0.018). Similarly, in a validation cohort of 101 men, the EPS model achieved an AUC of 0.749, which was significantly better than PSA's 0.577 (p < 0.001). Our model has demonstrated a potential reduction in unnecessary prostate biopsies by 26%, with only a 3% miss rate for csPCa cases, indicating its effectiveness in the Chinese population.

Study on membrane fouling mechanisms and mitigation strategies in a pilot-scale anaerobic membrane bioreactor (P-AnMBR) treating digestate.

Anaerobic Membrane Bioreactor (AnMBR) are employed for solid-liquid separation in wastewater treatment, enhancing process efficiency of digestion systems treating digestate. However, membrane fouling remains a primary challenge. This study operated a pilot-scale AnMBR (P-AnMBR) to treat high-concentration organic digestate, investigating system performance and fouling mechanisms. P-AnMBR operation reduced acid-producing bacteria and increased methane-producing bacteria on the membrane, preventing acid accumulation and ensuring stable operation. The P-AnMBR effectively removed COD and VFA, achieving removal rates of 82.3 % and 92.0 %, respectively. Higher retention of organic nitrogen and lower retention of ammonia nitrogen were observed. The membrane fouling consisted of organic substances (20.3 %), predominantly polysaccharides, and inorganic substances (79.7 %), primarily Mg ions (10.1 %) and Ca ions (4.5 %). To reduce the increased transmembrane pressure (TMP) caused by fouling (a 10.6-fold increase in filtration resistance), backwash frequency experiment was conducted. It revealed a 30-min backwash frequency minimized membrane flux decline, facilitating recovery to higher flux levels. The water produced amounted to 70.3 m³ over 52 days. The research provided theoretical guidance and practical support for engineering applications, offering practical insights for scaling up P-AnMBR.

Anaerobic degradation of pesticide wastewater: Improving sludge characteristics and reducing membrane fouling with combined tandem UASB+membrane system with high velocity settlers.

In this pilot study, a combined tandem UASB+membrane reactor (R2) with high velocity settlers was proposed for the treatment of pesticide wastewater at different hydraulic retention times (HRT) and compared with a control reactor (R1). The average COD removal efficiencies of the R2 at HRTs of 96, 72, and 48 h were 83.7 %, 82.8 %, and 74.2 %, which are 14 %, 17 %, and 21 % higher than those of the R1, respectively. Throughout the operation, the biogas production of R2 was 33 %, 19 % and 28 % higher than that of R1 at the same stage, respectively, and the methane yield of R2 (0.19-0.26 L CH4/gCODremoved) was improved by 10-17 % compared to that of R1. Mean α values (VFA/ALK) of 0.13∼0.22 indicated that R2 did not undergo acidification. R2 reduced the extracellular polymers (EPS) content in the attached sludge by 56-62 % compared to R1. It also successfully delayed membrane fouling rate by 19-22 %. The results demonstrate that the R2 has a high treatment capacity, stability, and methane recovery, while also effectively reducing membrane fouling.

Sludge bound-EPS solubilization enhance CH4 bioconversion and membrane fouling mitigation in electrochemical anaerobic membrane bioreactor: Insights from continuous operation and interpretable machine learning algorithms.

Bound extracellular polymeric substances (EPS) are complex, high-molecular-weight polymer mixtures that play a critical role in pore clogging, foulants adhesion, and fouling layer formation during membrane filtration, owing to their adhesive properties and gelation tendencies. In this study, a novel electrochemical anaerobic membrane bioreactor (EC-AnMBR) was constructed to investigate the effect of sludge bound-EPS solubilization on methane bioconversion and membrane fouling mitigation. During the 150-days' operation, the EC-AnMBR demonstrated remarkable performance, characterized by an exceptionally low fouling rate (transmembrane pressure (TMP) < 4.0 kPa) and high-quality effluent (COD removal > 98.2 %, protein removal > 97.7 %, and polysaccharide removal > 98.5 %). The highest methane productivity was up to 38.0 ± 3.1 mL/Lreactor/d at the applied voltage of 0.8 V with bound-EPS solubilization, 107.6 % higher than that of the control stage (18.3 ± 2.4 mL/Lreactor/d). Morphological and multiplex fluorescence labeling analyses revealed higher fluorescence intensities of proteins, polysaccharides, total cells and lipids on the surface of the fouling layer. In contrast, the interior exhibited increased compression density and reduced activity, likely attributable to compression effect. Under the synergistic influence of the electric field and bound-EPS solubilization, biomass characteristics exhibited a reduced propensity for membrane fouling. Furthermore, the bio-electrochemical regulation enhanced the electroactivity of microbial aggregates and enriched functional microorganisms, thereby promoting biofilm growth and direct interspecies electron transfer. Additionally, the potential hydrogenotrophic and methylotrophic methanogenesis pathways were enhanced at the cathode and anode surfaces, thereby increasing CH4 productivity. The random forest-based machine learning model analyzed the nonlinear contributions of EPS characteristics on methane productivity and TMP values, achieving R² values of 0.879 and 0.848, respectively. Shapley additive explanations (SHAP) analysis indicated that S-EPSPS and S-EPSPN were the most critical factors affecting CH4 productivity and membrane fouling, respectively. Partial dependence plot analysis further verified the marginal and interaction effects of different EPS layers on these outcomes. By combining continuous operation with interpretable machine learning algorithms, this study unveils the intricate impacts of EPS characteristics on methane productivity and membrane fouling behaviors, and provides new insights into sludge bound-EPS solubilization in EC-AnMBR.

Efficient alleviation granular sludge floatation in a high-rate anammox reactor by dosing folate.

Although granular floatation has been recognized as a significant issue hindering the application of high-rate anammox biotechnology, limited knowledge is available about its causes and control strategies. This study proposed a novel control strategy by adding folate, and demonstrated its role in the granular floatation alleviation through long-term operation and granular characterizations. It was found that the floatation of anammox granular sludge was obviously relieved with the decreased sludge floatation potential by 67.1% after dosing with folate (8 mg/L) at a high nitrogen loading rate of 12.3 kg-N/(m3·d). Physiochemical analyses showed that the decrease of extracellular polymeric substances (EPS) content (mainly protein), the alleviation of granular surface pore plugging in conjunction with the smooth discharge of generated nitrogen gas were collectively responsible for efficient floatation control. Moreover, metagenomic analysis suggested that the synergistic interactions between anammox bacteria and their symbionts were attenuated after dosing exogenous folate. Anammox bacteria would reduce their synergistic dependence on the symbionts, and decline the supply of metabolites (e.g., amino acids and carbohydrates in EPS) to symbiotic bacteria. The declined EPS excretion contributed to the alleviation of granular floatation by dredging pores blockage, thus leading to a stable system performance. The findings not only offer insights into the role of microbial interaction in granular sludge floatation, but also provide a feasible approach for controlling the floatation issue in anammox granular-based processes.

Characterization of emetic Bacillus cereus biofilm formation and cereulide production in biofilm.

Bacillus cereus is a well-known foodborne pathogen that can cause human diseases, including vomiting caused by emetic toxin, cereulide, requiring 105-108 cells per gram to cause the disease. The bacterial cells may be eliminated during processing, but cereulide can survive in most processing techniques due to its resistance to high temperatures, extreme pH and proteolytic enzymes. Herein, we reported dynamic processes of biofilm formation of four different types and cereulide production within the biofilm. Confocal laser scanning microscopy (CLSM) images revealed that biofilms of the four different types reach each stage at different time points. Among the extracellular polymeric substances (EPS) components of the four biofilms formed by the emetic B. cereus F4810/72 strain, proteins account for the majority. In addition, there are significant differences (p < 0.05) in the EPS components at the same stage among biofilms of different types. The time point at which cereulide was first detected in the four types of biofilms was 24 h. In the biofilm of B. cereus formed in ultra-high-temperature (UHT) milk, the first peak of cereulide appeared at 72 h. The cereulide content of the biofilms formed in BHI was mostly higher than that of the biofilms formed in UHT milk. This study contributes to a better understanding of food safety issues in the industry caused by biofilm and cereulide toxin produced by B. cereus.