Microbial Attachment Research Articles

A novel chitosan/biochar-modified eco-concrete with balanced mechanical, planting, and water purification performance for riparian restoration

The blocking between terrestrial and riverine ecosystems by impermeable concrete can cause negative impacts on plant growth, water quality, and biodiversity in riparian zones. Herein, pursuing a balance among mechanical, planting, and water purification property, chitosan/biochar-modified eco-concrete (CBEC) was prepared as a new sustainable alternative for riparian protection, ecological restoration and water quality improvement. Compressive strength of CBEC with an optimized chitosan/biochar content of 6% could reach up to 14.05 MPa, meeting the requirements for stabilizing riparian slopes. Micromorphology characterization and porosity measurement (29.63%) confirmed the abundantly porous structure of CBEC, facilitating the soil-water nutrient exchange, plant growth and microbial attachment. The 30-d water tank cultivation observed that the physiological parameters of T. orientalis planted in CBEC, including biomass, chlorophyll, protein and starch, were greatly improved compared to unmodified eco-concrete (EC). Moreover, compared to EC, biochar-modified EC and chitosan-modified EC, the planting CBEC could most effectively decrease the levels of TN, NH4+-N, TP, and COD by 53.82%, 62.50%, 88.31%, and 57.95%, respectively. Specially, the planting CBEC could degrade a common but recalcitrant pesticide nitenpyram (NTP) by 32.83% into low-toxic substances, recognized by LC-MS analysis. Microbiological analysis revealed that CBEC greatly promoted the proliferation of both nutrient-transforming bacteria (e.g., Nitrospira and Pseudomonas) and some specific species dominating NTP degradation (e.g., Rhodococcus and Bacillus). Also, PICRUSt2 prediction results identified the enrichment of functional genes related to nitrogen and phosphorus transformation. Our findings can not only develop a superior multi-performance eco-concrete material but also provide a promising strategy for sustainable riparian restoration.

Genome-Centric Metagenomics Insights into the Plastisphere-Driven Natural Degradation Characteristics and Mechanism of Biodegradable Plastics in Aquatic Environments.

Biodegradable plastics (BPs) are pervasively available as alternatives to traditional plastics, but their natural degradation characteristics and microbial-driven degradation mechanisms are poorly understood, especially in aquatic environments, the primary sink of plastic debris. Herein, the three-month dynamic degradation process of BPs (the copolymer of poly(butylene adipate-co-terephthalate) and polylactic acid (PLA) (PBAT/PLA) and single PLA) in a natural aquatic environment was investigated, with nonbiodegradable plastics polyvinyl chloride, polypropylene, and polystyrene as controls. PBAT/PLA showed the weight loss of 47.4% at 50 days and severe fragmentation within two months, but no significant decay for other plastics. The significant increase in the specific surface area and roughness and the weakening of hydrophobicity within the first month promoted microbial attachment to the PBAT/PLA surface. Then, a complete microbial succession occurred, including biofilm formation, maturation, and dispersion. Metagenomic analysis indicated that plastispheres selectively enriched degraders. Based on the functional genes involved in BPs degradation, a total of 16 high-quality metagenome-assembled genomes of degraders (mainly Burkholderiaceae) were recovered from the PBAT/PLA plastisphere. These microbes showed the greatest degrading potential at the biofilm maturation stage and executed the functions by PLA_depolymerase, polyesterase, hydrolase, and esterase. These findings will enhance understanding of BPs' environmental behavior and microbial roles on plastic degradation.

Tailoring surgical sutures with chitosan and non-thermal atmospheric plasma: biofunctionalization for antimicrobial efficacy and enhanced wound healing

Surgical sutures serve as medical devices designed to facilitate the closure of wounds by securing opposing tissues. While sutures are an integral part of the surgical healing process, also present favorable surfaces for microbial attachment, increasing surgical site infections (SSIs). In this study, sutures that have antimicrobial and improved wound healing properties are described as novel approaches for minimizing SSIs. The absorbable multifilament suture, poly (glycolic-co-lactic acid) (PGLA), and non-absorbable multifilament suture (silk) are treated with non-thermal atmospheric plasma (NTAP) and subsequently coated with chitosan/chitosan nanoparticles (Ch/ChNp). Suture samples are analyzed in terms of antibacterial properties, in vitro bioactivity, wound healing efficiency, mechanical strength, chemical characterization, and surface morphologies. Bacterial adherence of Staphylococcus aureus and Escherichia coli on both sutures is inhibited effectively due to the surface modification after plasma treatment. The NTAP treatment results in reduced wound healing for silk sutures without a selective effect on PGLA sutures. However, subsequent coating with Ch/ChNp significantly enhances wound healing for both sutures. Although the maximum tensile strength decreases after NTAP treatment, improves following the Ch/ChNp coating. Our findings indicate that the developed sutures demonstrate notable antimicrobial properties, enhance wound healing, and hold promise as a potential material for suturing applications.

The operating performance of Modified Basalt Fibers (MBF) bio-nest reactor exposed to nano-plastics

Biological nests made of Modified Basalt Fiber (MBF bio-nests) serve as effective carriers for enhancing wastewater treatment. However, little is known about their performance when exposed to nano-plastics. This study investigates the decontamination efficiency and microbial functionality of four types of MBF and traditional Basalt Fibers (BF) as carriers in contact oxidation reactors. Compared to BF, MBF demonstrated superior growth effects and biocompatibility within the bio-nest. Ca-MBF and Mn-MBF bio-nests exhibited the highest and most uniform absorption capacities, respectively, alongside increased secretion of total Extracellular Polymeric Substances (EPS) and higher Protein to Sugar (PN/PS) ratios. In sewage environments, all MBF groups displayed stable performance in removing NH4+-N and COD. Significant removal of TN and TP was notably observed in Mn-MBF treatments. Mn and Ca treatments predominantly influenced the Proteobacteria and Bacteroidetes phyla, crucial for nitrogen and phosphorus removal. Following exposure to nano-plastics, Mn-MBF and Ca-MBF treatments maintained high decontamination efficiency, particularly for TP and COD (48.64 % to 57.78 % and 90.91 % to 92.89 %, respectively). The significant removal of NH4+-N and TP only occurred in Mn-MBF and Ca-MBF treatments, which stimulated the growth of bacteria resistant to nano-plastics. Key genera such as Zoogloea and Meganema were identified as dominant, contributing to organic matter decomposition, EPS secretion, biofilm condensation, and enhanced microbial attachment. The findings underscore the structural stability enhancement of Mn-MBF and Ca-MBF bio-nests in contact oxidation reactors, demonstrating their resilience against nano-plastic pollution.

Fungal Attachment-Resistant Polymers for the Additive Manufacture of Medical Devices.

This study reports the development of the first copolymer material that (i) is resistant to fungal attachment and hence biofilm formation, (ii) operates via a nonkilling mechanism, i.e., avoids the use of antifungal actives and the emergence of fungal resistance, (iii) exhibits sufficient elasticity for use in flexible medical devices, and (iv) is suitable for 3D printing (3DP), enabling the production of safer, personalized medical devices. Candida albicans (C. albicans) can form biofilms on in-dwelling medical devices, leading to potentially fatal fungal infections in the human host. Poly(dimethylsiloxane) (PDMS) is a common material used for the manufacture of medical devices, such as voice prostheses, but it is prone to microbial attachment. Therefore, to deliver a fungal-resistant polymer with key physical properties similar to PDMS (e.g., flexibility), eight homopolymers and 30 subsequent copolymers with varying glass transition temperatures (Tg) and fungal antiattachment properties were synthesized and their materials/processing properties studied. Of the copolymers produced, triethylene glycol methyl ether methacrylate (TEGMA) copolymerized with (r)-α-acryloyloxy-β,β-dimethyl-γ-butyrolactone (AODMBA) at a 40:60 copolymer ratio was found to be the most promising candidate by meeting all of the above criteria. This included demonstrating the capability to successfully undergo 3DP by material jetting, via the printing of a voice prosthesis valve-flap using the selected copolymer.

Impacts of polystyrene nanoplastics on microgel formation from effluent organic matter

Municipal effluents discharged from wastewater treatment plants (WWTPs) are considered major contributors of nanoplastics (NPs) and dissolved effluent organic matter (dEfOM) to environments. Due to their small sizes, NPs can travel easily in waterways and evade wastewater treatment processes, and may directly interact with dEfOM, altering their environmental fates. However, although much research has examined the impact of natural organic matter on NPs, the interactions between NPs and dEfOM remain unexplored. This study investigated the influences of NPs on the behavior and capacity of dEfOM aggregation and surface granularity, and identified the possible aggregation mechanism. We also adjusted the salinity of water samples to simulate scenarios based on WWTP–sea continuums. Our data suggest that dEfOM can self-assemble with 55 nm polystyrene NPs to form microgels, particularly under high salinity conditions. NPs accelerates the formation speed and number of dEfOM aggregates, but the sizes of the aggregates remain largely unchanged. The relative particle counts at a salinity of 34 psu increased by 300 % compared to the control group. The potential mechanism behind NPs-microgels aggregation is likely driven by the synergistic effect of the divalent ion crosslinking and hydrophobic interactions between EfOM and NPs. Notably, NPs incorporation into microgels decreases the surface granularity, thereby possibly affecting settling velocity and colonization of aggregates, as well as microbial attachment and community diversity. Overall, our findings demonstrate the potential influence of NPs on dEfOM assembly and surface properties following effluent discharge, and can inspire further relevant studies on microorganism interactions, removal technologies, and the environmental transport of NPs.

Novel Indigenous Strains and Communities with Copper Bioleaching Potential from the Amolanas Mine, Chile

Bioleaching, a process catalyzed by acidophilic microorganisms, offers a sustainable approach to metal extraction from sulfide minerals. Chalcopyrite, the world’s most abundant copper sulfide, presents challenges due to surface passivation limiting its bioleaching efficiency. Also, indigenous species and microbial communities may present high copper extraction rates and offer new possibilities for application in bioleaching processes. This study examines the bioleaching potential of microbial isolates and communities obtained from Amolanas Mine in Chile. Samples were collected, cultivated, and identified by Sanger sequencing. The bioleaching potential and biofilm formation of isolates and enrichments were evaluated on pyrite and chalcopyrite. The results show the isolation of nine Leptospirillum and two Acidithiobacillus strains. The bioleaching experiments demonstrated good copper bioleaching potentials of the Leptospirillum I2CS27 strain and EICA consortium (composed mainly of Leptospirillum ferriphilum, Acidiphilium sp., and Sulfobacillus thermosulfidooxidans), with 11% and 25% copper recovery rates, respectively. Microbial attachment to the surface mineral was not mandatory for increasing the bioleaching rates. Our findings underscore the importance of indigenous microbial communities in enhancing copper bioleaching efficiency.

Efficient and sustained inhibition of ammonia nitrogen release from sediment in water by microbial self-aggregation zeolite layer.

Despite global efforts to manage water eutrophication, the continual release of ammonia nitrogen from sediments maintains the eutrophic state of water bodies, presenting serious challenges to the management. In order to find an efficient method for sediment remediation, the experiment of using signal molecules to enhance the adhesion of microorganisms on zeolite was carried out. Five different zeolitic ammonium adsorptions were examined using two different signal molecules, N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) and N-(β-ketocaproyl)-DL-homoserine lactone (C6), to enhance microbial attachment on two types of zeolites. The results showed that the modified microbial attached Z1 zeolite reinforced with signal molecule C6 had the best effect. The effect was better in the case of high ammonium adsorption, and the TN removal could reach 7.99mg·L-1 with an inhibition rate of 90.08%. The ammonia nitrogen removal reached 4.75mg·L-1 with an inhibition rate of 87.64%, and the ammonia nitrogen and total nitrogen of the overlying water reached the surface III water quality standard. In addition, the addition of the signal molecule increased the zeta potential on the surface of the bacterial colloid. In addition, the amount of protein I in the dissolved organic matter (DOM) fraction increased, improving microbial adhesion ability and facilitating their attachment to the zeolite surface. The signal molecule C6 could increase the zeta potential of microbial surface and promote the production of protein I, thus strengthening the attachment of zeolite biofilm and improving the water quality.

Exploring the potential of graphite material in an unplanted electroactive wetland for the remediation of synthetic wastewater containing azo dye.

The current study was conducted to understand the sole role of graphite as a substrate material in a dual-chambered baffled electroactive wetland (EW) in the treatment of Methyl red dye-containing wastewater. The results obtained were compared with conventional gravel-based unplanted dual-chambered constructed wetlands (CW) at a lab scale. The highest dye decolorisation and COD removal efficiency achieved was 92.88 ± 1.6% and 95.78 ± 4.1%, respectively, in the electro-active wetland. Dissolved oxygen (DO) and pH conditions were appropriately maintained in both the microcosms because of separated aerobic and anaerobic chambers. UV-vis and gas chromatography-mass spectroscopy analysis revealed the production of by-products like 4-amino benzoic and N- N dimethyl phenyl-diamine of MR in microcosms and revealed further mineralisation of by-products in the aerobic zone of electroactive-wetland. Higher root growth of Cicer aerietinum and Vigna radiata was observed in the presence of effluents of baffled electroactive wetlands compared to constructed wetland, indicating a decrease in phytotoxicity. Metagenomic analysis revealed the abundance of potential microbes for MR and organic matter removal from phylum Proteobacteria, Firmicutes, Bacteroidetes, and Euryarchaeota. A batch adsorption study revealed a higher adsorption capability of graphite material in comparison to gravel. Hence, this study demonstrated that graphite is an appropriate substrate in electroactive wetland in facilitating microbial attachments and enhancing dye degradation, in addition to exhibiting superior adsorption quality.

The oral microbiota and periodontal health in orthodontic patients.

The oral microbiota develops within the first 2 years of childhood and becomes distinct from the parents by 4 years-of-age. The oral microbiota plays an important role in the overall health/symbiosis of the individual. Deviations from the state of symbiosis leads to dysbiosis and an increased risk of pathogenicity. Deviations can occur not only from daily life activities but also from orthodontic interventions. Orthodontic appliances are formed from a variety of biomaterials. Once inserted, they serve as a breeding ground for microbial attachment, not only from new surface areas and crevices but also from material physicochemical interactions different than in the symbiotic state. Individuals undergoing orthodontic treatment show, compared with untreated people, qualitative and quantitative differences in activity within the oral microbiota, induced by increased retention of supra- and subgingival microbial plaque throughout the treatment period. These changes are at the root of the main undesirable effects, such as gingivitis, white spot lesions (WSL), and more severe caries lesions. Notably, the oral microbiota profile in the first weeks of orthodontic intervention might be a valuable indicator to predict and identify higher-risk individuals with respect to periodontal health and caries risk within an otherwise healthy population. Antimicrobial coatings have been used to dissuade microbes from adhering to the biomaterial; however, they disrupt the host microbiota, and several bacterial strains have become resistant. Smart biomaterials that can reduce the antimicrobial load preventing microbial adhesion to orthodontic appliances have shown promising results, but their complexity has kept many solutions from reaching the clinic. 3D printing technology provides opportunities for complex chemical syntheses to be performed uniformly, reducing the cost of producing smart biomaterials giving hope that they may reach the clinic in the near future. The purpose of this review is to emphasize the importance of the oral microbiota during orthodontic therapy and to use innovative technologies to better maintain its healthy balance during surgical procedures.

CO2 Laser-labeling on Fresh Produce: Evaluating Postharvest Quality, Microbial Safety, and Economic Analysis

Fresh produce is traditionally labeled with plastic price lookup (PLU) stickers that are attached to the produce surface using edible glue. However, both the stickers and glue are environmental contaminants, and the stickers can still easily detach from the produce surface during handling and disrupt traceability. An alternative method of labeling, the CO2 laser-labeling technology (LLT), has been gaining attention in recent years. However, engraving Quick Response (QR) code using LLT is unique, and the performance of this technology varies from produce item to produce item, and information on its effects on postharvest quality, microbial safety, and economic feasibility has not been reported. The objectives of this study were to investigate the effect of laser-labeling technology on (1) postharvest quality, (2) microbial safety, and (3) economic analysis of this technology. Three horticultural crops, ‘Red Delicious’ apple (Malus pumila), green bell pepper (Capsicum annuum), and cucumber (Cucumis sativus) were procured from a local grocery store. Each produce was engraved with a Quick Response (QR) code or 6-digit alphanumerical (text) code using the commercially available Trotec Speedy 300 CO2 laser engraver, followed by the application of edible wax. Fresh weight loss for laser-printed produce was higher compared to controls, but no difference in visual quality ratings was observed. The laser-labeled produce was assessed for microbial contamination by artificially inoculating rifampicin-resistant Escherichia coli (E. coli) log10 6 CFU/mL to the labeled fruit. The results showed that the population of rifampicin-resistant E. coli was statistically higher in all three products labeled with text code compared to the nontreated controls. The QR-coded treatments were similar to the controls. The wax application did not affect the microbial attachment on the laser-labeled produce. The CO2 laser labeling technology has the potential for industrial application.

Study of the Structure of Hyperbranched Polyglycerol Coatings and Their Antibiofouling and Antithrombotic Applications.

While blood-contacting materials are widely deployed in medicine in vascular stents, catheters, and cannulas, devices fail in situ because of thrombosis and restenosis. Furthermore, microbial attachment and biofilm formation is not an uncommon problem for medical devices. Even incremental improvements in hemocompatible materials can provide significant benefits for patients in terms of safety and patency as well as substantial cost savings. Herein, a novel but simple strategy is described for coating a range of medical materials, that can be applied to objects of complex geometry, involving plasma-grafting of an ultrathin hyperbranched polyglycerol coating (HPG). Plasma activation creates highly reactive surface oxygen moieties that readily react with glycidol. Irrespective of the substrate, coatings are uniform and pinhole free, comprising O─C─O repeats, with HPG chains packing in a fashion that holds reversibly binding proteins at the coating surface. In vitro assays with planar test samples show that HPG prevents platelet adhesion and activation, as well as reducing (>3 log) bacterial attachment and preventing biofilm formation. Ex vivo and preclinical studies show that HPG-coated nitinol stents do not elicit thrombosis or restenosis, nor complement or neutrophil activation. Subcutaneous implantation of HPG coated disks under the skin of mice shows no evidence of toxicity nor inflammation.

Superhydrophobic coatings reduce human bacterial foodborne pathogen attachment to woods used in fresh produce harvest and postharvest packing

Wood is reportedly more difficult to maintain in hygienic condition versus other food contact materials, yet its use in produce packing and retail warrants efforts to reduce the risk of microbial pathogen contamination and attachment. This study characterized antifouling capabilities of fluorinated silanes applied to wood used in fresh edible produce handling to render the wood superhydrophobic and less supportive of bacterial pathogen attachment. Pine and oak cubic coupon surfaces were treated with 1% (w/w) silane or left untreated. Treated and untreated coupons were inoculated with Salmonella enterica or Listeria monocytogenes and held to facilitate pathogen attachment for 1, 4, or 8 h. Silane treatment of wood produced significant reductions in the proportions of strongly attaching cells for both pathogens versus loosely attaching cells (P < 0.01). Salmonella attachment demonstrated a dependency on wood treatment; silane-treated wood supported a lower fraction of strongly adhering cells (1.87 ± 1.24 log CFU/cm2) versus untreated wood (3.72 ± 0.67 log CFU/cm2). L. monocytogenes demonstrated significant declines in strongly attaching cells during extended exposure to silane-treated wood, from 7.59 ± 0.14 to 5.27 ± 0.68 log CFU/cm2 over 8 h post-inoculation. Microscopic analysis demonstrated silane treatment increased the surface roughness of both woods, leading to superhydrophobic conditions on wood surfaces, consequently decreasing strong attachment of pathogenic bacteria.

Effect of postpolymerization time and atmosphere on surface properties and biofilm formation in additively manufactured resins for definitive restorations

ObjectivesTo investigate how postpolymerization time (PPT) and atmosphere (PPA) influence the surface properties, protein adsorption, and microbial adhesion of two types of additively manufactured (AM) resins used for definitive restorations. MethodsTwo different types of commercially available AM resins for definitive restorations (UR and CR) were used to create disk-shaped specimens. These specimens were divided into eight groups based on resin type (UR and CR), PPT (standard or extended), and PPA (air or nitrogen). After postpolymerization, the surface roughness (Ra and Sa) and surface free energy (SFE) of all specimens were measured. The study also evaluated protein adsorption, microbial attachment, and cytotoxicity. A non-parametric factorial analysis of variance with post-hoc analyses was conducted, using a significance level (α) of 0.05. ResultsThe Ra and Sa values for CR were higher than those for UR, regardless of PPT or PPA (P < 0.05). For UR, SFE was higher with extended PPT compared to standard PPT. CR had higher SFE than UR under standard PPT. The interaction between PPT and PPA had a significant effect on protein adsorption (P < 0.05). When PPT was standard, nitrogen significantly increased protein adsorption compared to air. The interaction between resin type and PPA, and between resin type and PPT, significantly affected microbial adhesion (P < 0.05). The changes in PPT or PPA did not affect the cytotoxicity of either AM resin. ConclusionSurface properties, protein adsorption, and microbial attachment were influenced by the interactions among PPT, PPA, and resin type. These factors can have implications for resin-based definitive restorations. Clinical significancesClinicians should understand the impact of PPT and PPA on the surface properties of AM resins for definitive restorations, particularly regarding protein adsorption and microbial adhesion. Additionally, the type of AM resin (based on chemical composition) could affect its biological properties.

Selective microbial attachment to LDPE plastic beads during passage through the wastewater network

Urban wastewater treatment plants (WWTP) represent key point-source discharges of microplastics (MP) into the environment, however, little is known about the microbial carrying capacity of plastics travelling through them. The purpose of this study was to quantify the number of cells that become associated with MP at different locations within a WWTP, and to assess differences in microbiome communities. We conducted a field experiment incubating low density polyethylene (LDPE) MP beads in WWTP influent and effluent, as well as tracking free floating beads during passage in wastewater from a large municipal hospital to an urban WWTP, where they were subsequently recovered. Using two cell counting methods - automated flow cytometric true absolute cell counts and indirect cell quantification via protein content based on a model E. coli cell - we quantified cell attachment to LDPE beads. LDPE associated counts ranged from 350 × 103 cells cm−2 after incubation in wastewater effluent, and 990 × 103 cells cm−2 after incubation in wastewater influent. 16S rRNA gene amplicon sequencing was used to determine the bacterial community structure of the plastic-associated microbiomes. Our results showed that distinct bacterial communities developed on the LDPE MP following exposure to each wastewater type. Influent (untreated) wastewater LDPE-associated microbiomes were dominated by Bacillota whereas the microbes that attached in wastewater effluent (tertiary treated) were dominated by Pseudomonadota. In conclusion, this study provides clear evidence that microplastics migrating through the sewer network and WWTP rapidly accumulate microbiomes with unique microbial community structures varying from sewage influent to effluent. These findings demonstrate the differential microbiological risk from MP associated with routine wastewater discharges to those released from intermittent combined sewer overflows (CSOs) during storm events.

Effects of bagasse as a carbon source on biofloc formation, water quality, and microbial community structure in shrimp culture system.

As a widely available, low-cost agricultural byproduct, bagasse is a potential solid carbon source and provides microbial attachment as a biofilm carrier. In this study, the effects of bagasse as a carbon source on biofloc formation, water quality, microbial community structure, and nitrogen conversion in a shrimp culture system were explored, and the performance of bagasse bioflocs was assessed. No bagasse was added to the control group (CK), and three bagasse addition groups were set up, with the floc content of the water maintained at 5 mL/L (BF5 group), 10 mL/L (BF10 group), and 15 mL/L (BF15 group). The results showed that bagasse bioflocs formed in the fourth week when bagasse was placed in the culture water, and the surface of bagasse was covered with thick biofilm at that time. The DOC content of the BF15 group was significantly greater than that of the CK group, from 30.31 to 105.06% (P < 0.05), and the DOC increased with increasing bagasse biofloc content. The BF group rapidly converted TAN to NO2--N and then to NO3--N because the accumulation of nitrite nitrogen in the BF15 group occurred 1 week earlier than in the other groups; at the 8th week, the nitrite nitrogen conversion rate of each BF group was close to 100%, which was significantly greater than that of the CK group (P < 0.05). The relative abundances of genes encoding microbial glutamate dehydrogenase and glutamate synthase increased in the bagasse biofloc groups (P < 0.05). The relative abundances of genes from Rhodobacterales and Hyphomicrobiales in each group were greater, but bagasse bioflocs increased the proportion of Hyphomicrobiale. In summary, adding bagasse to the shrimp culture system can form a biofloc system, resulting in the formation of a rich bacterial biofilm on its surface. Bagasse addition not only affects the composition of microbial communities but also accelerates the nitrification process in water. As a result, ammonia and nitrite are converted into nitrate, which is essential for maintaining the stability of the ecosystem balance in aquaculture water.

Silver nanowire-doped conductive polymer hydrogel anode for increasing electron transfer and COD removal rate simultaneously in microbial fuel cell

Microbial fuel cell (MFC) can generate electrons through microbial metabolism of organic matter in sewage. In this paper, carbon felt as base material, the conductive polymers polyaniline and polypyrrole combined with silver nanowires were doped in hydrogel, a super hydrophilicity, low electron transfer resistance, good biocompatibility hydrogel MFC anode (PANI-PPy-Ag NWs/CF) were prepared. It showed a hand-torn bread structure, this three-dimensional (3D) porous structure increased microbial attachment amount. The anode could reach a maximum voltage output of 0.66 V in only 5.5 h, and produce a maximum power density of 2196.61 mW/m3. Due to the doping of silver nanowire, a new electronic mode was explored, coulomb efficiency of 31.01 % and an ultra-high COD removal rate (96.69 %) was obtained. This study introduces a conductive composite hydrogel MFC anode, which provides a new idea for the material diversity, electrical production and sewage removal performance of MFC anode.

Comparative Evaluation of the Fluoride Releasing Ability and Microbial Attachment of Glass-Hybrid Restorative Material

This study aimed to compare the fluoride-releasing ability and degree of microbial attachment of a newly developed glass-hybrid restorative material (GH) with those of a high-viscosity glass ionomer (HvGIC), resin-modified glass ionomer (RMGI), and composite resin (CR). In addition, the correlation between fluoride-releasing ability and microbial attachment between materials was evaluated. Specimens were prepared in a disc shape and divided into 4 groups according to the materials (GH, HvGIC, RMGI, and CR). The fluoride release experiments were performed in each group (n = 15). The amount of fluoride released was measured on days 1, 3, 7, 14, 28, and 42 after storage. For the microbial attachment experiment, 12 specimens were produced per group using &lt;i&gt;Mutans Streptococci&lt;/i&gt; (&lt;i&gt;S.mutans&lt;/i&gt; ), a cariogenic microorganism. &lt;i&gt;S. mutans&lt;/i&gt; was cultured on the specimens for 24 hours, and the number of bacteria was measured. GH had the highest cumulative fluoride release and showed a significant difference when compared with RMGI (&lt;i&gt;p&lt;/i&gt; = 0.001) and CR (&lt;i&gt;p&lt;/i&gt; &lt; 0.0001). Microbial attachment was the lowest in GH; however, no significant difference was observed between the materials (&lt;i&gt;p&lt;/i&gt; = 0.169). There was no significant correlation between fluoride release from materials and microbial attachment (&lt;i&gt;p&lt;/i&gt; &gt; 0.05). From this perspective, remineralization of low-mineralized areas could be expected due to the high fluoride release of GH, and the effect of delaying the progression of dental caries could be predicted from the low cariogenic microbial attachment. Therefore, GH might be a useful restorative material for treating immature permanent teeth with hypomineralized enamel. However, further studies are needed about the degree of remineralization of hypomineralized areas after restoration and the capacity to recharge fluoride.

The efficiency of enhanced nitrogen and phosphorus removal in a vertical flow constructed wetland using alkaline modified corn cobs as a carbon source

Adding carbon sources to constructed wetlands can improve nitrogen removal efficiency. Modifying plant biomass can solve problems such as excessive release of nitrogen, phosphorus, and organic matter in the initial stage and insufficient carbon supply in the later stage. This article utilized alkali-modified corn cob as a carbon source to construct vertical flow constructed wetlands and to study the carbon release characteristics of alkali-modified corn cob, as well as its removal effect on organic matter in wastewater. The results indicated that the solid-to-liquid ratio in the alkali modification process of corn cob was 1:10, and it was found that the best treatment method for alkali modified corn cob was to use a sodium hydroxide concentration of 2%, a treatment time of 12 h, and a temperature of 20 °C. Its surface roughness increases, which is beneficial for releasing carbon sources and promoting the growth of microbial attachment. Furthermore, the porosity also increases and. Intermittent aeration could significantly enhance the removal of NH4+-N, and TP in constructed wetlands. The average removal rates of NH4+-N and TP were 60.93% and 89.50%, respectively, and the average removal rates of COD, NO3--N and TN were 60.67%, 98.38% and 83.73%, respectively. At the same time, alkali-modified corn cobs were used as carbon sources. It can effectively remove NO3--N and promote denitrification in constructed wetlands.

Bacterial biofilm formation in seafood: Mechanisms and inhibition through novel non‐thermal techniques

AbstractSeafoods are susceptible to microbial contamination due to their high moisture, nutrient contents and neutral pH. Among various microorganisms, biofilm‐forming bacteria pose a severe threat to the seafood supply chain as well as consumer health. Bacterial biofilm formation in seafood is primarily caused by Aeromonas hydrophila, Vibrio cholerae, V. vulnificus, V. parahaemolyticus, Salmonella spp., and Listeria monocytogenes. Biofilm formation is an important protective mechanism of microorganisms causing spoilage of seafood and disease threats to consumers. The attachment of microbes on the surface of seafood followed by the growth and proliferation of bacterial cells leads to the production of exopolymer compounds and the formation of biofilm. This biofilm is difficult to destroy or inhibit through conventional prevention/destruction techniques. The occurrence of bacterial strains/biofilms with more resistance to different preventive strategies is a big challenge for the seafood processing industry. This review covers the mechanisms of biofilm formation by bacteria and various non‐thermal processing approaches to prevent microbial contamination and biofilm formation in seafood products. The aforementioned non‐thermal processing techniques for the destruction of biofilm and quality control of seafood products include cold plasma treatment, irradiation, pulsed electric field technology, hydrostatic pressure processing, photosensitisation, natural bioactive compounds and so on. All these techniques effectively inhibit the bacterial biofilm and microbial growth without altering sensorial properties. However, further research validation and applications at the industry level are still required.