• Journal of Veterinary Science
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• v.25 no.2
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• pp.30.1-30.16
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• 2024

Background: Biofilms, such as those from Staphylococcus epidermidis, are generally insensitive to traditional antimicrobial agents, making it difficult to inhibit their formation. Although quercetin has excellent antibiofilm effects, its clinical applications are limited by the lack of sustained and targeted release at the site of S. epidermidis infection. Objectives: Polyethylene glycol-quercetin nanoparticles (PQ-NPs)-loaded gelatin-N,O-carboxymethyl chitosan (N,O-CMCS) composite nanogels were prepared and assessed for the on-demand release potential for reducing S. epidermidis biofilm formation. Methods: The formation mechanism, physicochemical characterization, and antibiofilm activity of PQ-nanogels against S. epidermidis were studied. Results: Physicochemical characterization confirmed that PQ-nanogels had been prepared by the electrostatic interactions between gelatin and N,O-CMCS with sodium tripolyphosphate. The PQ-nanogels exhibited obvious pH and gelatinase-responsive to achieve on-demand release in the micro-environment (pH 5.5 and gelatinase) of S. epidermidis. In addition, PQ-nanogels had excellent antibiofilm activity, and the potential antibiofilm mechanism may enhance its antibiofilm activity by reducing its relative biofilm formation, surface hydrophobicity, exopolysaccharides production, and eDNA production. Conclusions: This study will guide the development of the dual responsiveness (pH and gelatinase) of nanogels to achieve on-demand release for reducing S. epidermidis biofilm formation.

• Membrane and Water Treatment
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• v.15 no.2
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• pp.59-66
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• 2024

This study evaluated the performance of a membrane aerated biofilm reactor (MABR) for nitrogen removal from a high-strength ammonia nitrogen-containing wastewater. The experimental setup consisted of four compartments that are sequentially anaerobic and aerobic to achieve complete nitrogen removal. The last compartment of the reactor setup contained a membrane bioreactor (MBR) to reduce sludge production in the system and to obtain a better-quality effluent. Continuous experiment over a period of 47 days showed that MABR exhibited excellent NH₄⁺-N removal efficiency (99.5%) compared to the control setup without MABR (56.5%). The final effluent NH₄⁺-N concentration obtained in the MABR was 2.99±1.56 mg/L. In contrast to NH₄⁺-N removal, comparable TOC removal values in the MABR and the control reactor (99.2% and 99.3%, respectively) showed that air supply through MABR is much more critical for denitrification than for organic removal. Further study to understand the effect of air supply rate and holding pressure on NH₄⁺-N removal in MABR revealed that an increase in both these parameters positively impacted reactor performance. These parameters are related to oxygen supply to the biofilm formed over the membrane surface, which in turn influenced NH₄⁺-N removal in MABR. Among the two different strategies to control biofilm over the membrane surface, results showed that scouring for a duration of 10 min on a weekly basis, along with mixing air supply, could be an effective method.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.2
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• pp.149-157
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• 2022

The aim of this study was to evaluate the effects of erythrosine-mediated photodynamic therapy (PDT) on Streptococcus mutans biofilm recovery by counting its colony-forming units (CFUs) and via confocal laser scanning microscopy analysis at different time points following PDT. In PDT, photosensitizer was an erythrosine. S. mutans ATCC25175 biofilms were irradiated using an LED curing light. Chlorhexidine (CHX) was used as positive control. After each antimicrobial treatment, samples were cultured to allow biofilm recovery. Viability was measured by calculating the CFU counts after treatment and after every 3 hours for up to 24 hours. Immediately after treatment, the PDT and CHX groups showed equally significant decreases in S. mutans CFU counts compared to the negative control. After 12 hours of reculture, the PDT group showed no significant difference in the decrease in CFU count compared to the negative control, whereas the CHX group showed significantly lower CFU counts throughout the 24-hour period. Erythrosine-mediated PDT can effectively inhibit S. mutans biofilm formation. However, biofilm recovery occurred earlier in the CHX group after PDT. This study provides insights into the clinical effectiveness of PDT in preventing dental caries.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.253-262
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• 2016

Streptococcus mutans (S. mutans) is one of the most important bacteria in the formation of dental plaque and dental caries. S. mutans adheres to an acquired pellicle formed on the tooth surface, and aggregates with many oral bacteria. It initiates plaque formation by synthesizing glucan from sucrose, which is catalyzed by glucosyltransferases. Propolis is a resinous mixture produced by honeybees, by mixing saliva and beeswax with secretions gathered from wood sap and flower pollen. Bees prevent pathogenic invasions by coating the propolis to the outer and inner surface of the honeycomb. Propolis has traditionally been used for the treatment of allergic rhinitis, asthma and dermatitis. We investigated the inhibitory effects of propolis ethanol extract on biofilm formation and gene expression of S. mutans. The biofilm formation of S. mutans was determined by scanning electron microscopy (SEM) and safranin staining. We observed that the extract of propolis had an inhibitory effect on the formation of S. mutans biofilms at concentrations higher than 0.2 mg/ml. Real-time PCR analysis showed that the gene expression of biofilm formation, such as gbpB, spaP, brpA, relA and vicR of S. mutans, was significantly decreased in a dose dependent manner. The ethanol extract of propolis showed concentration dependent growth inhibition of S. mutans, and significant inhibition of acid production at concentrations of 0.025, 0.05, 0.1 and 0.2 mg/ml, compared to the control group. These results suggest that the ethanol extract of propolis inhibits gene expression related to biofilm formation in S. mutans.

• Journal of Microbiology and Biotechnology
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• v.24 no.11
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• pp.1574-1582
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• 2014

Bacteria recognize changes in their population density by sensing the concentration of signal molecules, N-acyl-homoserine lactones (AHLs). AHL-mediated quorum sensing (QS) plays a key role in biofilm formation, so the interference of QS, referred to as quorum quenching (QQ), has received a great deal of attention. A QQ strategy can be applied to membrane bioreactors (MBRs) for advanced wastewater treatment to control biofouling. To isolate QQ bacteria that can inhibit biofilm formation, we isolated diverse AHL-degrading bacteria from a laboratory-scale MBR and sludge from real wastewater treatment plants. A total of 225 AHL-degrading bacteria were isolated from the sludge sample by enrichment culture. Afipia sp., Acinetobacter sp. and Streptococcus sp. strains produced the intracellular QQ enzyme, whereas Pseudomonas sp., Micrococcus sp. and Staphylococcus sp. produced the extracellular QQ enzyme. In case of Microbacterium sp. and Rhodococcus sp., AHL-degrading activities were detected in the whole-cell assay and Rhodococcus sp. showed AHL-degrading activity in cell-free lysate as well. There has been no report for AHL-degrading capability in the case of Streptococcus sp. and Afipia sp. strains. Finally, inhibition of biofilm formation by isolated QQ bacteria or enzymes was observed on glass slides and 96-well microtiter plates using crystal violet staining. QQ strains or enzymes not only inhibited initial biofilm development but also reduced established biofilms.

• Journal of dental hygiene science
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• v.18 no.2
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• pp.69-75
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• 2018

The purpose of our study is to compare the adhesion and biofilm formation abilities of isolates from water discharged from dental unit waterlines (DUWLs). Bacteria were isolated from a total of 15 DUWLs. Twelve isolates were selected for the experiment. To confirm the adhesion ability of the isolates, each isolate was attached to a glass coverslip using a 12-well plate. Plates were incubated at $26^{\circ}C$ for 7 days, and the degree of adhesion of each isolate was scored. To verify the biofilm formation ability of each isolate, biofilms were allowed to form on a 96-well polystyrene flat-bottom microtiter plate. The biofilm accumulations of all isolates formed at $26^{\circ}C$ for 7 days were identified and compared. A total of 56 strains were isolated from 15 water samples including 12 genera and 31 species. Of the 56 isolates, 12 isolates were selected according to the genus and used in the experiment. Sphingomonas echinoides, Methylobacterium aquaticum, and Cupriavidus pauculus had the highest adhesion ability scores of +3 among 12 isolates. Among these three isolates, the biofilm accumulation of C. pauculus was the highest and that of S. echinoides was the third-most abundant. The lowest biofilm accumulations were identified in Microbacterium testaceum and M. aquaticum. Most isolates with high adhesion ability also exhibited high biofilm formation ability. Analysis of adhesion and biofilm formation of the isolates from DUWLs can provide useful information to understand the mechanism of DUWL biofilm formation and development.

• Korean Journal of Environmental Biology
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• v.19 no.2
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• pp.101-105
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• 2001

The biodeterioration with blue-green algae has been studied since 1997 up to 2000 in the tomb of King Mooryong in Kongiu, Korea. Biodeterioration in the tomb initially started from the formation of micro-organismic biofilm that had been suggested to make minor changes on the stone surface. This study revealed that the biofilm formed by microorganisms could result in permanent damages on stone cultural properties. The application of a chemical, 'K2Ol', developed by the author successfully removed fouling of biofilm on the surfaces of stone cultural properties. When small pieces of granite stone were embedded in the solution to study the side effects of the chemicals for a period of three months, the mechanical stability was 0.97 compared to control and there was no change in color. Biodeterioration is one of the most harmful factors that decrease the value of stone cultural properties but it may be treated with a development of proper chemicals.

• Membrane and Water Treatment
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• v.10 no.6
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• pp.395-404
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• 2019

The influence of chlorine on marine bacterial communities was examined in this study. A non-chlorine-adapted marine bacterial community (NCAM) and a chlorine-adapted bacterial community (CAM, bacterial community treated with $0.2mg-Cl_2/L$ chlorine) were cultivated for 1 month. A distinct difference was observed between the NCAM and CAM, which shared only eight operational taxonomic units (OTUs), corresponding to 13.1% of the total number of identified OTUs. This result suggested that chlorine was responsible for the changes in the marine bacterial communities. Kordiimonas aquimaris was found to be a chlorine-resistant marine bacterium. The effect of intermittent chlorination on the two marine biofilm communities formed on the reverse osmosis (RO) membrane surface was investigated using various chlorine concentrations (0, 0.2, 0.4, 0.6 and 0.8 mg $Cl_2/L$). Although the average number of adherent marine bacteria on the RO membrane over a period of 7 weeks decreased with increasing chlorine concentration, disinfection efficiencies showed substantial fluctuations throughout the experiment. This is due to chlorine depletion that occurs during intermittent chlorination. These results suggest that intermittent chlorination is not an effective disinfection strategy to control biofilm formation.

• Journal of the korean academy of Pediatric Dentistry
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• v.51 no.1
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• pp.32-39
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• 2024

This study evaluated the additive impact of ethylenediamine tetraacetic acid (EDTA) on erythrosine-mediated photodynamic therapy (PDT) against Streptococcus mutans (S. mutans) biofilm by measuring colony-forming units and applying confocal laser scanning microscopy. Fifty-six bovine incisors, free from dental caries or structural defects, were utilized in this study. Dentin specimens were created by cutting with a low-speed diamond disk under a continuous flow of water, resulting in dimensions of 6.0 mm × 3.0 mm × 2.0 mm. The specimens were categorized into 4 groups: Control, EDTA, PDT, and EDTA + PDT. S. mutans ATCC 25175 was employed to establish biofilm on the dentin specimens. A 17% EDTA solution was applied for 1 min. For PDT, erythrosine served as the photosensitizer. Finally, a light-emitting diode source (385 - 515 nm) was employed in this study. The PDT group exhibited a significantly lower bacterial count than both the control and EDTA groups (p < 0.001). The EDTA + PDT group demonstrated a significantly reduced bacterial count compared to the other 3 groups (p < 0.001). This study demonstrated that EDTA enhances the antimicrobial efficacy of PDT on S. mutans biofilm. Even at a low concentration of photosensitizer, the combination of EDTA and PDT yields a significant antibacterial effect.

• Membrane Journal
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• v.31 no.5
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• pp.327-332
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• 2021

The use of membranes for MBRWG (Membrane Bioreactor for Waste Gas) treatment can provide highly selective separation of a waste gas stream followed by effective biological removal. MBRWG have several potential advantages, among which the most distinctive one is separation of gas and liquid phases at each side of membrane potentially allowing the optimal biomass control toward effective biodegradation of target gases as well as biofilm activation. This advantage becomes especially favorable for removal of hydrophobic toxic gases, such as xylene, by MBRWG systems, because the mass transfer, the toxicity, and thereby the biodegradation of hydrophobic gas treatment requires sensitive handling of liquid stream and water control near biofilm. Among various membranes for MBRWG treatment, PDMS-hollow fiber membranes provide the high gas mass transfer. Despite lower specific surface areas, capillary type membranes are also applied current MBRWG studies. In addition to the main application of membranes as biofilm supporter in MBRWG systems, there can be another application of membranes in a posterior process for removal of residual gases or dusts emitted from conventional biological waste gas treatment processes.