Effects of salinity and betaine addition on anaerobic granular sludge properties and microbial community succession patterns in organic saline wastewater.

In this study, the effects of different salinity gradients and addition of compatible solutes on anaerobic treated effluent water qualities, sludge characteristics and microbial communities were investigated. The increase in salinity resulted in a decrease in particle size of the granular sludge, which was concentrated in the range of 0.5-1.0 mm. The content of EPS (extracellular polymeric substances) in the granular sludge gradually increased with increasing salinity and the addition of betaine (a typical compatible solute). Meanwhile, the microbial community structure was significantly affected by salinity, with high salinity reducing the diversity of bacteria. At higher salinity, Patescibacteria and Proteobacteria gradually became the dominant phylum, with relative abundance increasing to 13.53% and 12.16% at 20 g/L salinity. Desulfobacterota and its subordinate Desulfovibrio, which secrete EPS in large quantities, dominated significantly after betaine addition.Their relative abundance reached 13.65% and 7.86% at phylum level and genus level. The effect of these changes on the treated effluent was shown as the average chemical oxygen demand (COD) removal rate decreased from 82.10% to 79.71%, 78.01%, 68.51% and 64.55% when the salinity gradually increased from 2 g/L to 6, 10, 16 and 20 g/L. At the salinity of 20 g/L, average COD removal increased to 71.65% by the addition of 2 mmol/L betaine. The gradient elevated salinity and the exogenous addition of betaine played an important role in achieving stability of the anaerobic system in a highly saline environment, which provided a feasible strategy for anaerobic treatment of organic saline wastewater.

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.

Effect of settling time and organic loading rates on aerobic granulation processes treating high strength wastewater.

Despite its numerous advantages, the aerobic granular sludge (AGS) process faces several challenges that hinder its widespread implementation. One such challenge is the requirement for high organic load ratios (OLR), which significantly impacts AGS formation and stability, posing a barrier to commercialization. In response to these challenges, this study investigates the granulation and treatment efficacy of the AGS process for treating high-concentration wastewater under various OLR and settling time. Three sequential batch reactors (R1, R2, R3) were operated at OLRs of 0.167, 0.33, and 1 kg COD/m3·day. The study focuses on analyzing key parameters including sludge characteristics, extracellular polymeric substances (EPS) content, PN/PS ratio, and microbial clusters. Results demonstrate that reducing settling time from 90 to 30 min enhances sludge settleability, resulting in a maximum 50.8 % decrease in SVI30 (from 98.1 to 122.8 mL/g to 51.9-81.3 mL/g), thereby facilitating the selection of beneficial microorganisms during granulation. Particularly, at R2, the PN/PS ratio was 4.3, and EPS content increased by 1.52-fold, leading to a 1.41-fold increase in sludge attachment. This observation suggests a progressive maturation of AGS. Additionally, analysis of microbial diversity and cluster composition highlights the influence of OLR variations on the ratios of Proteobacteria and Bacteroidetes. These findings emphasize the significant impact of SBR operational strategies on AGS process performance and biological stability, offering valuable insights for the efficient operation of future high-concentration wastewater treatment processes.

Effect of cations on aerobic granulation for sidestream treatment.

Aerobic granular sludge (AGS) represents an aggregate of sludge formed through the self-immobilization of microorganisms under aerobic conditions. It is currently under scrutiny for its potential as a technology to reduce carbon emissions and promote sustainability. The practicality of AGS stems from its ability to encourage granule formation and enhance structural stability. In this study, a total of five cations (K+, Ca2+, Mg2+, Al3+, Fe3+) were introduced to facilitate stable structuring and the formation of granules for treating high-strength wastewater, such as side-stream treatment. As a result of the experiment, the loosely bound extracellular polymeric substances (LB-EPS) content in the cation-enhanced sludge witnessed a significant increase, leading to elevated total EPS content under all experimental conditions. Furthermore, the protein (PN)/polysaccharide (PS) ratio, a pivotal component of EPS influencing AGS's hydrophobicity and structural stability, exhibited a collective increase, with Mg2+ reaching the highest value of 1.7. The relationship between relative hydrophobicity and the PN/PS ratio was found to strongly impact sludge adhesion, with noteworthy results observed particularly for Mg2+, Al3+, and Fe3+. The viability of attached cells reached 96.8 %, the highest recorded in the case of Mg2+. In the context of treating high-strength wastewater, Mg2+ emerged as the optimal cation for accelerating AGS formation and enhancing structural stability.

Promotion of aromatic amino acids of extracellular polymeric substance targeted transformation via sulfite mediated iron redox cycling in sludge solid-liquid separation.

Highly hydrophilic extracellular polymeric substance (EPS) with gel-like structure seriously plagues the development of sludge deep dewatering. Oxysulfur radicals-based oxidation driven by iron-bearing mineral proposes a promising strategy for effective EPS decomposition. However, the transformation and involved interaction mechanisms of aromatic proteins are still controversial due to the complex EPS structure. Herein, sulfite mediated siderite (denoted as Fe(II)/S(IV)) was developed for targeted transformation aromatic amino acids in EPS oxidation to strengthen sludge solid-liquid separation. The enhanced sludge dewaterability were benefited from the Fe(II)/S(IV) bonded interaction assisted by Fe3+/Fe2+ as redox interface that facilitating the release of intracellular bound water via diminish the hydrophily and bind strength with solid protons. The amide region nitrogen of aromatic amino acids (especially tyrosine and tryptophan) originating from EPS presented looser structure and lower spatial site resistance, which were attributed to the exposure of hydrophobic sites in amino groups after Fe(II)/S(IV) treatment. Furthermore, the effective decline of aromatic amino acids in inner layer-EPS (loosely bound EPS and tightly bound EPS) was directed from Fe-N targeted interaction by triggering a series of sulfate-based radical chain reactions. The good correlation between electron transfer amount (R2 = 0.926) and Fe-N (R2 = 0.925) with bonding interaction demonstrated that the complexation of aromatic amino acids with Fe sites on siderite/sulfite via Fe-N bonds, accounting for efficient sludge solid-liquid separation. This study deepens the understanding of sludge organic matter targeted transformation and provides a tactic for iron-based conditioning of sludge.

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.

Investigating the interaction of uranium(VI) with diatoms and their bacterial community: A microscopic and spectroscopic study.

Diatoms and bacteria play a vital role in investigating the ecological effects of heavy metals in the environment. Despite separate studies on metal interactions with diatoms and bacteria, there is a significant gap in research regarding heavy metal interactions within a diatom-bacterium system, which closely mirrors natural conditions. In this study, we aim to address this gap by examining the interaction of uranium(VI) (U(VI)) with Achnanthidium saprophilum freshwater diatoms and their natural bacterial community, primarily consisting of four successfully isolated bacterial strains (Acidovorax facilis, Agrobacterium fabrum, Brevundimonas mediterranea, and Pseudomonas peli) from the diatom culture. Uranium (U) bio-association experiments were performed both on the xenic A. saprophilum culture and on the four bacterial isolates. Scanning electron microscopy and transmission electron microscopy coupled with spectrum imaging analysis based on energy-dispersive X-ray spectroscopy revealed a clear co-localization of U and phosphorus both on the surface and inside A. saprophilum diatoms and the associated bacterial cells. Time-resolved laser-induced fluorescence spectroscopy with parallel factor analysis identified similar U(VI) binding motifs both on A. saprophilum diatoms and the four bacterial isolates. This is the first work providing valuable microscopic and spectroscopic data on U localization and speciation within a diatom-bacterium system, demonstrating the contribution of the co-occurring bacteria to the overall interaction with U, a factor non-negligible for future modeling and assessment of radiological effects on living microorganisms.

Interaction between microalgae and phycosphere bacteria in a binary cultivation system-based dairy farm wastewater treatment.

The combination of microalgal culture and wastewater treatment is an emerging topic. This study investigated the use of different microalgae to treat different types of dairy farm wastewater. The results showed that the removal of ammonia nitrogen and total phosphorus by mixed microalgae was over 99% and 80%, respectively. The highest production of protein in biomass and extracellular polymeric substances was observed in high-concentration wastewater. In the phycosphere, the abundance of Proteobacteria and Cyanobacteria increased, while that of Bacteroidota decreased. Phycosphere bacteria were strongly correlated with microalgal growth and the composition of extracellular polymeric substances, especially with bound extracellular polymeric substances relative to soluble extracellular polymeric substances. Genes associated with photosynthesis and respiration in phycosphere bacteria were upregulated, contributing to the material exchange capacity in the microalgal-bacterial systems. The interaction between microalgae and phycosphere bacteria thus represents the core of the binary cultivation system-based wastewater treatment and requires further investigation.

Role of diffusible signal factor in regulating aerobic granular sludge formation under temperature shocks.

Signal-molecule-mediated strategies are proposed for aerobic granular sludge (AGS), but the regulatory mechanisms behind AGS formation are largely unexplored. In this study, two sequence batch reactors (SBRs) were operated to investigate the regulation of diffusible signal factor (DSF) in AGS formation. DSF secretion in Reactor 2 (R2: 10 °C→25 °C) decreased by 15 % compared to Reactor 1 (R1: 25 °C→10 °C), correlating with a 26 % increase in extracellular polymeric substance (EPS) concentration, resulting in a 63 % acceleration of the granulation process. After temperature shocks in R2, DSF concentration increased by 70 %, while EPS concentration decreased by 47 %. Batch tests confirmed that DSF inhibited EPS secretion. Combined 16S rRNA analysis and machine learning identified key bacteria responsible for secreting EPS and signal molecule. The decrease in the abundances of these bacteria reduced EPS production. These findings on DSF regulation of EPS secretion provide an in-depth understanding of enhanced AGS granulation.

Multi-dimensional perspectives into the pervasive role of microbial extracellular polymeric substances in electron transport processes.

During the process of biological treatment, most microorganisms are encapsulated in extracellular polymeric substances (EPS), which protect the cell from adverse environments and aid in microbial attachment. Microorganisms utilize extracellular electron transfer (EET) for energy and information interchange with other cells and the outside environment. Understanding the role of steric EPS in EET is critical for studying microbiology and utilizing microorganisms in biogeochemical processes, pollutant transformation, and bioenergy generation. However, the current study shows that understanding the roles of EPS in the EET processes still needs a great deal of research. In view of recent research, this work aims to systematically summarize the production and functional group composition of microbial EPS. Additionally, EET pathways and the role of EPS in EET processes are detailed. Then factors impacting EET processes in EPS are then discussed, with a focus on the spatial structure and composition of EPS, conductive materials and environmental pollution, including antibiotics, pH and minerals. Finally, strategies to enhance EET, as well as current challenges and future prospects are outlined in detail. This review offers novel insights into the roles of EPS in biological electron transport and the application of microorganisms in pollutant transformation.

An integrated preventive and therapeutic magnetic nanoparticle loaded with rhamnolipid and vancomycin for combating subgingival biofilms.

OBJECTIVES: Mechanical debridement supplemented with antibacterial agents effectively eradicates subgingival biofilms formed in the periodontal pockets of severe periodontitis patients. However, the available antimicrobial agents have limited penetrating ability to kill the bacteria encased in the deep layers of biofilms. This study aimed to fabricate a novel magnetic nanoparticle (MNP) loaded with rhamnolipid (RL) and vancomycin (Vanc, Vanc/RL-Ag@Fe3O4) to combat subgingival biofilms. METHODS: The multispecies subgingival biofilm was formed by periodontal pathogens, including Streptococcus oralis (S. oralis), Streptococcus sanguinis (S. sanguinis), Actinomyces naeslundii (A. naeslundii), Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum). Scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM), and quantitative real-time polymerase chain reaction (qRT-PCR) were used to determine the anti-biofilm efficacy of Vanc/RL-Ag@Fe3O4 with or without a magnetic field on multispecies subgingival biofilms. RESULTS: The minimal inhibitory concentration (MIC) values of Vanc/RL-Ag@Fe3O4 on S. oralis, S. sanguinis, A. naeslundii, P. gingivalis, and F. nucleatum were 25, 50, 100, 50, and 25 µg/mL, respectively. Vanc/RL-Ag@Fe3O4 (200 µg/mL) reduced the 7-d biofilm thickness from 22 to 13 µm by degrading extracellular polymeric substance (EPS) and killing most bacteria except for tolerant F. nucleatum. A magnetic field enhanced the anti-biofilm effect of Vanc/RL-Ag@Fe3O4 by facilitating its penetration into the bottom layers of biofilms and killing tolerant F. nucleatum. SIGNIFICANCE: Vanc/RL-Ag@Fe3O4 MNPs can release RL, Vanc, and Ag and eradicate subgingival biofilms by disrupting EPS and killing bacteria. Vanc/RL-Ag@Fe3O4 combined with a magnetic force is a promising approach for combating periodontal infection.

Enhanced short-chain fatty acid production from sludge anaerobic fermentation by combined pretreatment with sodium pyrophosphate and thermal hydrolysis.

The slow breakdown of sludge is the primary obstacle hindering the conversion of waste-activated sludge to short-chain fatty acids (SCFAs) by anaerobic fermentation. This study proposed a novel method incorporating sodium pyrophosphate and thermal hydrolysis (SP-TH) for sludge pretreatment and evaluated its effectiveness regarding SCFA production. The combined pretreatment of SP at 0.4 g/g of total suspended solids and TH at 140 °C enhanced SCFA production from 2,169 ± 208 to 4,388 ± 184 mg chemical oxygen demand/L. SP strips extracellular polymeric substances, and the subsequent TH decomposes cells in the sludge, thus promoting sludge hydrolysis. SP-TH pretreatment promoted SCFA accumulation by enhancing enzyme activity and enriching acidifying bacteria. This study demonstrated that SP-TH pretreatment can effectively promote acid production from sludge, providing a new avenue for organic matter recovery through sludge anaerobic fermentation pretreatment.

Insight into enhancing the performance of sludge dewatering using a novel flocculant CS-TA prepared through free radical-mediated conjugation.

Flocculation is one of the most significant conditioning methods for sludge dewatering. In the study, a novel flocculant CS-TA, prepared through free radical-mediated conjugation of tannic acid (TA) and chitosan (CS), was proposed to improve sludge dewatering. The characterisation using Fourier transform infra-red spectroscopy and X-ray diffraction analysis shows that the CS chain was the backbone of CS-TA, and the presence of CS-TA aromatic rings confirmed the conjugation of CS with TA. Moreover, the conditioning of CS-TA yielded the best dewatering performance at 30 mg g TS-1 with the water content of sludge cake by press filtration (Wsc) of 59.78% ± 0.3% and capillary suction time (CST) of 11.8s ± 0.35 s, compared to 98.2% ± 0.15% and 56.2 s ± 0.16 in raw sludge. The results of different influencing factors (e.g. pH and temperature) on flocculation efficiency indicated that CS-TA possessed the capacity for enhancing sludge dewaterability over a wide range of pH, and the optimal temperature was observed to be 35 °C. Furthermore, the increase of particle size and zeta potential implied the addition of CS-TA favoured the formation of larger particles charge neutralisation and adsorption bridging effect. In addition, extracellular polymer substances (EPS) analysis indicated that the decrease in the polysaccharide and protein contents in EPS after CS-TA addition could increase the relative hydrophobicity of sludge. Moreover, the contents of heavy metals in sludge and their leaching toxicity and environmental risk were reduced. This study provides comprehensive insights into the exploration of CS-TA for sludge dewatering and the maintenance of ecological security in an eco-friendly.

Enhancement of Biological Nitrogen Removal System Resilience to Chronic Exposure of Zinc Oxide Nanoparticles by Quorum Sensing Modulation: Physiochemical, Microbial, and Metabolic Insights.

The effects of three typical N-acyl-homoserine lactones (AHLs) on the tolerance of biological nitrogen removal (BNR) system to chronic exposure of zinc oxide nanoparticles (NPs) were investigated. C4-HSL successfully delayed the crash time of nitrogen removal performances in the NP-stressed system, while C6-HSL and C10-HSL maintained total nitrogen removal efficiencies throughout the 90-day NP exposure. All three AHLs increased NPs' contents captured in extracellular polymeric substances, alleviating membrane damage and preserving floc structure. The activities of tricarboxylic acid cycle-related enzymes and the relative abundances of BNR-related functional genes and genera were significantly enhanced. Besides, C6-HSL and C10-HSL augmented antioxidant enzyme activities and the abundances of functional genes and metabolites related to antioxidation, flagellar assembly, and chemotaxis, which synergistically reduced the reactive oxygen species' excessive accumulation. The tested AHLs effectively enhanced BNR systems' tolerance to chronic NP exposure, providing inspiration for quorum sensing applications in emerging contaminant removal.

Effects of long-term exposure to zinc on performances of anaerobic digesters for swine wastewater treatment under various organic loading rates.

The long-term performance of anaerobic digestion (AD) often decreases substantially when treating swine wastewater contaminated with heavy metals. However, the toxicological characteristics and mechanisms of continuous exposure to heavy metals under different organic loading rates (OLR) are still poorly understood. In these semi-continuous AD experiments, it was found that zinc concentrations of 40 mg/L only deteriorated the reductive environments of AD. In comparison, a concentration of 2.0 mg/L probably facilitated the reproduction of microorganisms in the operating digesters with a constant OLR of 0.51 g COD/(L·d). Nevertheless, when the OLR was increased to 2.30 g COD/(L·d), 2.0 mg/L zinc inhibited various life activities of microorganisms at the molecular level within only 10 days. Hence, even though 2.0 mg/L zinc could promote AD performances from a macroscopic perspective, it had potential inhibitory effects on AD. Therefore, this study deepens the understanding of the inhibitions caused by heavy metals on AD and the metabolic laws of anaerobic microorganisms in swine wastewater treatment. These results could be referred to for enhancing AD in the presence of zinc in practical swine wastewater treatment.

Effect of Novel and Traditional Intracanal Medicaments on Biofilm Viability and Composition.

INTRODUCTION: The aim of this study was to test the hypothesis that a combination of D-amino acids (DAAs) and trans-cinnamaldehyde (TC) demonstrates superior antibiofilm activity to calcium hydroxide (CH) and untreated controls. METHODS: In this 3-part in vitro study, the concentration of DAAs (D-methionine, D-leucine, D-tyrosine, and D-tryptophan) that would significantly decrease Enterococcus faecalis and Actinomyces naeslundii biofilm biomass was first determined. Then, the effect of TC + selected DAAs on polymicrobial biofilms was characterized by quantifying the biomass and biofilm viability. Finally, the antibiofilm effects of TC + DAA was compared with CH and untreated controls by (i) determining bacterial viability and (ii) quantifying biofilm matrix composition using selective fluorescence-binding analysis. Statistical analysis was performed using one-way ANOVA and appropriate multiple comparisons test, with P < .05 considered as statistically significant. RESULTS: TC (0.06%) + D-tyrosine (1 mM) + D-tryptophan (25 mM) significantly reduced the biomass and biofilm viability compared to the control (P < .05). While no significant difference was observed between TC + DAA and CH in the cultivable bacterial counts (P > .05), confocal microscopy demonstrated a significantly greater percentage of dead bacteria in TC + DAA-treated biofilms compared to CH and the control (P < .05). TC + DAA significantly decreased the biovolume and all the examined components of the biofilm matrix quantity compared to the control, while CH significantly reduced only the exopolysaccharide quantity (P < .05). CONCLUSION: The combination of TC + D-tyrosine + D-tryptophan demonstrated superior antibiofilm activity (biofilm bacterial killing and reduction of matrix quantity) to CH and has potential to be developed as an intracanal medicament.

Efficacy and mechanisms of rotating algal biofilm system in remediation of soy sauce wastewater.

This study investigated the efficacy of the rotating algal biofilm (RAB) for treating soy sauce wastewater (SW) and its related treatment mechanisms. The RAB system demonstrated superior nutrient removal (chemical oxygen demand, ammonium nitrogen, total nitrogen, and phosphorus for 92 %, 94 %, 91 %, and 82 %, respectively) and biofilm productivity (14 g m-2 d-1) at optimized 5-day harvest time and 2-day hydraulic retention time. This was mainly attributed to the synergistic interactions within the algae-fungi (Apiotrichum)-bacteria (Acinetobacter and Rhizobia) consortium, which effectively assimilated certain extracellular polymeric substances into biomass to enhance algal biofilm growth. Increased algal productivity notably improved protein and essential amino acid contents in the biomass, suggesting a potential for animal feed applications. This study not only demonstrates a sustainable approach for managing SW but also provides insight into the nutrient removal and biomass conversion, offering a viable strategy for large-scale applications in nutrient recovery and wastewater treatment.

[Applications of biofilm in environmental pollution control and the related challenges]. / 生物膜在环境污染治理中的应用及挑战.

Biofilm has been used in environmental pollution control in recent years due to its characteristics of adsorption and biodegradation. Beyond the success of its utilization in wastewater treatment, biofilm technique has high application value in the remediation of heavy metals and organic pollutants in soils. With the extensive attention and research of emerging pollutants such as microplastics and antibiotic resistance genes (ARGs), the pivotal role of biofilm can not be overlooked. Here, we presented a comprehensive review of the structure, formation mecha-nism, population, and functional aspects of biofilm, as well as its applications and mechanisms in environmental pollution control in recent years. We emphatically discussed the removal mechanism and application progress of biofilm on heavy metals and organic pollutants. We further expounded some novel environmental challenges posed by biofilm under new circumstances, including the coexistence of various pollutants in plastisphere, the spread of ARGs, and the accumulation of pathogens. Finally, we put forward the gaps of current research and prospects for future research, especially the importance of exploring the interaction relationship and mechanism between biofilm and various pollutants. It is expected to provide theoretical basis for the development of new technology of biofilm remediation.

Integrated remediation and detoxification of triclocarban-contaminated water using waste-derived biochar-immobilized cells by long-term column experiments.

Triclocarban (TCC), an antibacterial agent commonly used in personal care products, is one of the top ten contaminants of emerging concern in various environmental media, including soil and contaminated water in vadose zone. This study aimed to investigate TCC-contaminated water remediation using biochar-immobilized bacterial cells. Pseudomonas fluorescens strain MC46 (MC46), an efficient TCC-degrading isolate, was chosen, whereas agro-industrial carbonized waste as biochar was directly used as a sustainable cell immobilization carrier. According to the long-term TCC removal performance results (160 d), the biochar-immobilized cells consistently exhibited high TCC removal efficiencies (84-97%), whereas the free MC46 removed TCC for 76-94%. At 100 days, the detachment of the MC46 cells from the immobilized cell column was observed. The micro-Fourier-transform infrared spectroscopy results indicated that extracellular polymeric substance (EPS) was produced, but polysaccharide and protein fractions were washed out of the column. The lipid fraction of EPS adhered to the biochar, promoting TCC sorption for long-term treatment. The shortening of MC46 cells improved the tolerance of TCC toxicity. The TCC-contaminated water was successfully detoxified by the biochar-immobilized MC46 cells. Overall, the waste-derived biochar-immobilized cell system proposed in this study for the removal of emerging contaminants, including TCC, is efficient, economical, and aligned with the sustainable development concept of value-added utilization of waste.

Effect of mutanase and dextranase on biofilms of cariogenic bacteria: A systematic review of in vitro studies.

Matrix-degrading enzymes are promising non-biocidal adjuncts to dental biofilm control and caries prevention. By disrupting the biofilm matrix structure, enzymes may prevent biofilm formation or disperse established biofilms without compromising the microbial homeostasis in the mouth. This study reviewed whether treatment with mutanase and/or dextranase inhibits cariogenic biofilm growth and/or removes cariogenic biofilms in vitro. An electronic search was conducted in PubMed, EMBASE, Scopus, Web of Science, Cochrane, and LIVIVO databases. Manual searches were performed to identify additional records. Studies that quantitatively measured the effect of mutanase and/or dextranase on the inhibition/removal of in vitro cariogenic biofilms were considered eligible for inclusion. Out of 809 screened records, 34 articles investigating the effect of dextranase (n = 23), mutanase (n = 10), and/or combined enzyme treatment (n = 7) were included in the review. The overall risk of bias of the included studies was moderate. Most investigations used simple biofilm models based on one or few bacterial species and employed treatment times ≥30 min. The current evidence suggests that mutanase and dextranase, applied as single or combined treatment, are able to both inhibit and remove in vitro cariogenic biofilms. The pooled data indicate that enzymes are more effective for biofilm inhibition than removal, and an overall higher effect of mutanase compared to dextranase was observed.