Magnetic hollow fibers of covalent organic frameworks (COF) for pollutant degradation and adsorptive removal.

The shaping of covalent organic frameworks (COFs) from non-processible powder forms into applicable architectures with additional functionality remains a challenge. Using pre-electrospun polymer fibers as a sacrificial template, herein, we report a green synthesis of an architecture in the form of COF hollow fibers with an inner layer of peroxidase-like iron oxide nanoparticles as a catalytic material. When compared to peroxidase-like pristine iron oxide nanoparticles, these COF hollow fibers demonstrate higher catalytic breakdown of crystal violet due to their peroxidase-like activity via advanced oxidation process.

Precipitation-based microscale enzyme reactors coupled with porous and adhesive elastomer for effective bacterial decontamination and membrane antifouling on-demand.

Bacterial contamination of water environments can cause various troubles in various areas. As one of potential solutions, we develop enzyme-immobilized elastomer, and demonstrate the uses of enzyme reactions on-demand for effective microbial decontamination and antifouling. Asymmetrically-structured elastomer is prepared by combining two polydimethylsiloxane (PDMS) layers with different degrees of crosslinking: highly-crosslinked and lightly-crosslinked PDMS layers.

Glucose oxidase-copper hybrid nanoflowers embedded with magnetic nanoparticles as an effective antibacterial agent.

Bacterial contamination causes various problems ranging from bacterial infection to biofouling. As an effective and non-toxic agent for bacterial de-contamination, glucose oxidase (GOx)-copper hybrid nanoflowers embedded with amine-functionalized magnetic nanoparticles (NH-MNPs), called 'MNP-GOx NFs', are developed. Positively-charged NH-MNPs and negatively-charged GOx molecules are first interacted via electrostatic attraction which can be controlled by changing the buffer pH, and the follow-up addition of copper(II) sulfate leads to blooming of nanoflowers (MNP-GOx NFs) after incubation at room temperature for 3 days.

Enzyme-Immobilized Chitosan Nanoparticles as Environmentally Friendly and Highly Effective Antimicrobial Agents.

Highly effective and minimally toxic antimicrobial agents have been prepared by immobilizing glucose oxidase (GOx) onto biocompatible chitosan nanoparticles (CS-NPs). CS-NPs were prepared via ionotropic gelation and used for the immobilization of GOx via approaches of covalent attachment (CA), enzyme coating (EC), enzyme precipitate coating (EPC), and magnetic nanoparticle-incorporated EPC (Mag-EPC). EPC represents an approach consisting of enzyme covalent attachment, precipitation, and cross-linking, with CA and EC being control samples while Mag-EPC was prepared by mixing magnetic nanoparticles (Mag) with enzymes during the preparation of EPC.

Tyrosinase-immobilized CNT based biosensor for highly-sensitive detection of phenolic compounds.

Highly sensitive phenol biosensor was developed by using well-dispersed carbon nanotubes (CNTs) in enzyme solution and adding CNTs in enzyme electrodes. First, the intact CNTs were dispersed in aqueous tyrosinase (TYR) solution, and TYR molecules were precipitated and crosslinked to prepare the sample of enzyme adsorption, precipitation and crosslinking (EAPC). EAPC exhibited 10.

Enhancement of operating flux in a membrane bio-reactor coupled with a mechanical sieve unit.

Filtration flux is one of the key factors in regulating the performance of membrane bio-reactors (MBRs) for wastewater treatment. In this study, we explore the effectiveness of a mechanical sieve unit for effective flux enhancement through retardation of the fouling effect in a modified MBR system (SiMBR). In brief, the coarse sieve unit having 100 μm and 50 μm permits small size microorganism flocs to adjust the biomass concentration from the suspended basin to the membrane basin.

Immobilization and Stabilization of Acylase on Carboxylated Polyaniline Nanofibers for Highly Effective Antifouling Application via Quorum Quenching.

Acylase (AC) was immobilized and stabilized on carboxylated polyaniline nanofibers (cPANFs) for the development of antifouling nanobiocatalysts with high enzyme loading and stability. AC was immobilized via three different approaches: covalent attachment (CA), enzyme coating (EC), and magnetically separable enzyme precipitate coating (Mag-EPC). The enzyme activity per unit weight of cPANFs with Mag-EPC was 75 and 300 times higher than that of those with CA and EC, respectively, representing improved enzyme loading in the form of Mag-EPC.

Effective antifouling using quorum-quenching acylase stabilized in magnetically-separable mesoporous silica.

Highly effective antifouling was achieved by immobilizing and stabilizing an acylase, disrupting bacterial cell-to-cell communication, in the form of cross-linked enzymes in magnetically separable mesoporous silica. This so-called "quorum-quenching" acylase (AC) was adsorbed into spherical mesoporous silica (S-MPS) with magnetic nanoparticles (Mag-S-MPS), and further cross-linked for the preparation of nanoscale enzyme reactors of AC in Mag-S-MPS (NER-AC/Mag-S-MPS). NER-AC effectively stabilized the AC activity under rigorous shaking at 200 rpm for 1 month, while free and adsorbed AC lost more than 90% of their initial activities in the same condition within 1 and 10 days, respectively.

Design of quorum quenching microbial vessel to enhance cell viability for biofouling control in membrane bioreactor.

Quorum quenching (QQ) with a microbial vessel has recently been reported as an economically feasible biofouling control platform in a membrane bioreactor (MBR) for wastewater treatment. In this study, a quorum quenching MBR with a ceramic microbial vessel (CMV) was designed to overcome the extremely low F/M ratio inside a microbial vessel. The CMV was prepared with a monolithic ceramic microporous membrane and AHLdegrading QQ bacteria, Pseudomonas sp.

Biofouling control with bead-entrapped quorum quenching bacteria in membrane bioreactors: physical and biological effects.

Recently, interspecies quorum quenching by bacterial cells encapsulated in a vessel was described and shown to be efficient and economically feasible for biofouling control in membrane bioreactors (MBRs). In this study, free-moving beads entrapped with quorum quenching bacteria were applied to the inhibition of biofouling in a MBR. Cell entrapping beads (CEBs) with a porous microstructure were prepared by entrapping quorum quenching bacteria ( Rhodococcus sp.

Microbial population dynamics and proteomics in membrane bioreactors with enzymatic quorum quenching.

Quorum sensing gives rise to biofilm formation on the membrane surface, which in turn causes a loss of water permeability in membrane bioreactors (MBRs) for wastewater treatment. Enzymatic quorum quenching was reported to successfully inhibit the formation of biofilm in MBRs through the decomposition of signal molecules, N-acyl homoserine lactones (AHLs). The aim of this study was to elucidate the mechanisms of quorum quenching in more detail in terms of microbial population dynamics and proteomics.

Control of membrane biofouling in MBR for wastewater treatment by quorum quenching bacteria encapsulated in microporous membrane.

Recently, enzymatic quorum quenching has proven its potential as an innovative approach for biofouling control in the membrane bioreactor (MBR) for advanced wastewater treatment. However, practical issues on the cost and stability of enzymes are yet to be solved, which requires more effective quorum quenching methods. In this study, a novel quorum quenching strategy, interspecies quorum quenching by bacterial cell, was elaborated and proved to be efficient and economically feasible biofouling control in MBR.

Enzyme-immobilized nanofiltration membrane to mitigate biofouling based on quorum quenching.

Recently, enzymatic quorum quenching (in the form of a free enzyme or an immobilized form on a bead) was successfully applied to a submerged membrane bioreactor with a microfiltration membrane for wastewater treatment as a novel approach to control membrane biofouling. In this study, a quorum quenching enzyme (acylase) was directly immobilized onto a nanofiltration membrane to mitigate biofouling in a nanofiltration process. In a flow cell experiment, the acylase-immobilized membrane with quorum quenching activity prohibited the formation of mushroom-shaped mature biofilm due to the reduced secretion of extracellular polymeric substances (EPS).

Magnetic enzyme carrier for effective biofouling control in the membrane bioreactor based on enzymatic quorum quenching.

Quorum quenching, enzymatic quenching of bacterial quorum sensing, has recently proven its potential as a novel approach of biofouling control in the membrane bioreactor (MBR) for advanced wastewater treatment. However, the short catalytic lifetime and difficulty in recovering free enzyme hamper the successful application of the quorum quenching technique in the MBR under a long-term continuous operation. In this study, a magnetic enzyme carrier (MEC) was prepared by immobilizing the quorum quenching enzyme (acylase) on magnetic particles to overcome the technical limitations of free enzyme.

Quorum sensing: a new biofouling control paradigm in a membrane bioreactor for advanced wastewater treatment.

Bacteria regulate specific group behaviors such as biofilm formation in response to population density using small signal molecules called autoinducers (quorum sensing, QS). In this study, the concept of bacterial QS was applied to membrane bioreactors (MBRs) for advanced wastewater treatment as a new biofouling control paradigm. The research was conducted in three phases: (1) demonstrate the presence of the autoinducer signal in MBRs, (2) correlate QS activity and membrane biofouling, (3) apply QS-based membrane biofouling control.

Correlating TMP increases with microbial characteristics in the bio-cake on the membrane surface in a membrane bioreactor.

Subcritical flux operation is widely practiced in membrane bioreactors (MBRs) to avoid severe membrane fouling and, thus, to maintain sustainable permeability. Filtration at a constant subcritical flux, however, usually leads to a two-stage increase in the transmembrane pressure (TMP): initially slowly, then abruptly. We have investigated the mechanism of this two-stage TMP increase through analyses of the structure and microbial characteristics of the bio-cake formed on the membrane.

The effects of intermittent aeration on the characteristics of bio-cake layers in a membrane bioreactor.

The effects of a sequencing variation for dissolved oxygen (DO) concentrations on the membrane permeability in a submerged membrane bioreactor (MBR) were studied. An MBR was continuously operated under alternating DO conditions, e.g.

Characterization of biofilm structure and its effect on membrane permeability in MBR for dye wastewater treatment.

Two membrane bioreactors were operated at aerobic (DO=6.0mg/L) and anoxic (DO<0.3mg/L) conditions for the treatment of synthetic dye wastewater to determine the effect of dissolved oxygen on membrane filterability.

Membrane coupled high-performance compact reactor: a new MBR system for advanced wastewater treatment.

This study examined the potential and limitations of a new submerged membrane system coupled with a High-performance Compact Reactor (HCR) to take advantages of both systems. The configuration and installation position in the HCR of the membrane module were thoroughly investigated for the optimum design of a submerged membrane coupled with HCR, e.g.