Am Jang

Characterization and evaluation of aerobic granules in sequencing batch reactor

In order to investigate the aerobic granules cultured under alternating aerobic and anoxic conditions, a sequencing batch reactor (SBR) was operated without the presence of a carrier material. Nitrification and denitrification occurred alternately in the SBR operation, with an increased nitrification efficiency of up to 97% and a high chemical oxygen demand (COD) removal efficiency of up to 95%. It was observed that physical characteristics of granule play an important role in the performance of the SBR process. Light microscopy was used to observe the time dependent development of the granules in the SBR. Based on the microscopic observations, some floc-like sludges remained in the form of a mixture with granules for 30 days of operation. Even though various granule sizes had been formed in the reactor after 50 days, the granule sizes were primarily from 1 +/- 0.35 to 1.3 +/- 0.45 mm, rarely exceeding 2 mm. The granules were analyzed by a combination of microelectrodes and fluorescent in situ hybridization (FISH), which provides more detailed information on what happens inside the granules. Based on their results, ammonia oxidizing bacteria (AOB) existed primarily in the upper and middle layers of the granule. Assuming a first-order reaction for nitrification, most of the nitrification is likely to occur from the surface to 300 microm into the granular thickness.

State-of-the-art lab chip sensors for environmental water monitoring

As a result of increased water demand and water pollution, both surface water and groundwater quantity and quality are of major concern worldwide. In particular, the presence of nutrients and heavy metals in water is a serious threat to human health. The initial step for the effective management of surface waters and groundwater requires regular, continuous monitoring of water quality in terms of contaminant distribution and source identification. Because of this, there is a need for screening and monitoring measurements of these compounds at contaminated areas. However, traditional monitoring techniques are typically still based on laboratory analyses of representative field-collected samples; this necessitates considerable effort and expense, and the sample may change before analysis. Furthermore, currently available equipment is so large that it cannot usually be made portable. Alternatively, lab chip and electrochemical sensing-based portable monitoring systems appear well suited to complement standard analytical methods for a number of environmental monitoring applications. In addition, this type of portable system could save tremendous amounts of time, reagent, and sample if it is installed at contaminated sites such as Superfund sites (the USAs worst toxic waste sites) and Resource Conservation and Recovery Act (RCRA) facilities or in rivers and lakes. Accordingly, state-of-the-art monitoring equipment is necessary for accurate assessments of water quality. This article reviews details on our development of these lab-on-a-chip (LOC) sensors.

Immobilization of lysozyme-CLEA onto electrospun chitosan nanofiber for effective antibacterial applications.

Chitosan (CS) nanofibers with a diameter of 150-200nm were fabricated from a mixed chitosan/poly (vinyl alcohol) (PVA) solution by the electrospinning method. The nascent CS/PVA nanofibers were treated with 0.5M NaOH solution to make stable CS nanofibers by removing PVA under aqueous conditions. Hen egg-white lysozyme was immobilized on electrospun CS nanofibers via cross-linked enzyme aggregates (CLEAs) and used for effective and continuous antibacterial applications. The maximum amount of lysozyme immobilized on the CS nanofibers was determined to be 62.3mg/g of nanofibers under the optimum conditions. The immobilized lysozyme-CLEA retained more than 75.4% of its initial activity after 80 days of storage at room temperature, while the free lysozyme lost all of its activity under the same conditions. In addition, the immobilized lysozyme-CLEA retained more than 76% of its activity after 100 consecutive uses. Finally, the durability of the lysozyme-CLEA immobilized CS nanofibers showed bacteriostasis ratios of 82.4%, 79.8%, 83.4%, and 84.1% after 10 cycles against 4 pathogenic bacteria, viz. Staphylococcus aureus, Bacillus subtilis, Shigella flexneri, and Psedomonas aeruginosa, respectively. These results demonstrated that lysozyme-CLEA immobilized CS nanofibers could be used as a promising material for enhanced and continuous antibacterial applications.

Bead-Based Competitive Fluorescence Immunoassay for Sensitive and Rapid Diagnosis of Cyanotoxin Risk in Drinking Water

Due to the increased occurrence of cyanobacterial blooms and their toxins in drinking water sources, effective management based on a sensitive and rapid analytical method is in high demand for security of safe water sources and environmental human health. Here, a competitive fluorescence immunoassay of microcystin-LR (MCYST-LR) is developed in an attempt to improve the sensitivity, analysis time, and ease-of-manipulation of analysis. To serve this aim, a bead-based suspension assay was introduced based on two major sensing elements: an antibody-conjugated quantum dot (QD) detection probe and an antigen-immobilized magnetic bead (MB) competitor. The assay was composed of three steps: the competitive immunological reaction of QD detection probes against analytes and MB competitors, magnetic separation and washing, and the optical signal generation of QDs. The fluorescence intensity was found to be inversely proportional to the MCYST-LR concentration. Under optimized conditions, the proposed assay performed well for the identification and quantitative analysis of MCYST-LR (within 30 min in the range of 0.42-25 μg/L, with a limit of detection of 0.03 μg/L). It is thus expected that this enhanced assay can contribute both to the sensitive and rapid diagnosis of cyanotoxin risk in drinking water and effective management procedures.

Potentiometric and voltammetric polymer lab chip sensors for determination of nitrate, pH and Cd(II) in water

Due to their toxicity to humans and animals, heavy metals and nitrate in groundwater are of particular concern. The combination of high toxicity and widespread occurrence has created a pressing need for effective monitoring and measurement of nitrate and heavy metals in soil pore water and groundwater at shallow depths. In this work, a new electrochemical sensing platform with the self-assembly nanobeads-packed (nBP) hetero columns has been developed for the pH and nitrate measurements. In addition, for on-site determination of cadmium (Cd(II)), a bismuth (Bi(III)) based polymer lab chip sensor using the square-wave anodic stripping voltammetry (SWASV) sensing principle has been designed, fabricated and successfully characterized. Factors affecting sensitivity and precision of the sensor, including deposition potential and deposition time, were studied. Miniaturized electrochemical lab chip sensors could be very valuable in environmental monitoring area due to their many benefits, such as greatly reduced sensing cost, sensing system portability, and ease of use.

Study on the initial velocity distribution of exhaled air from coughing and speaking.

Abstract Increasing concerns about the spread of airborne pathogens such as severe acute respiratory syndrome (SARS) and novel swine-origin influenza A (H1N1) have attracted public attention to bioaerosols and protection against them. The airborne pathogens are likely to be expelled from coughing or speaking, so the physical data of the exhaled particles plays a key role in analyzing the pathway of airborne viruses. The objective of this study was to analyze the initial velocity and the angle of the exhaled airflow from coughing and speaking of 17 males and 9 females using Particle Image Velocimetry (PIV) and acrylic indoor chamber. The results showed that the average initial coughing velocity was 15.3m/s for the males and 10.6m/s for the females, while the average initial speaking velocity was 4.07m/s and 2.31m/s respectively. The angle of the exhaled air from coughing was around 38° for the males and 32° for the females, while that of the exhaled air from speaking was around 49° and 78° respectively. Also, the linear relation between the tested subject’s height and their coughing and speaking velocity was shown in this study.

The role of a combined coagulation and disk filtration process as a pre-treatment to microfiltration and reverse osmosis membranes in a municipal wastewater pilot plant

A pilot study was conducted to assess the performance of a municipal wastewater reclamation plant consisting of a combined coagulation-disk filtration (CC-DF) process, microfiltration (MF) and reverse osmosis (RO) membranes, in terms of the removal of water contaminants and changes in characteristics of effluent organic matter (EfOM). The CC-DF and MF membranes were not effective for the removal of dissolved water contaminants. However, they could partially reduce the turbidity associated with the cake layer formation by particulate materials on the membrane surfaces. Furthermore, most of water contaminants were completely removed by the RO membranes. Although the CC-DF process could remove approximately 20% of turbidity, the aluminium concentrations considerably increased after the CC-DF process due to the residual coagulants complexed with both carboxylic acid and alcohol functional groups of EfOM. Those aluminium-EfOM complexes had a lower negative charge and higher molecular weight (>0.1 μm pore size of the MF membranes) compared to non-complexed EfOM. These results indicate that the control of the formation of the aluminium-EfOM complexes should be considered as a key step to use the CC-DF process as a pre-treatment of the MF and RO membranes for mitigation of membrane fouling in the tested pilot plant.

An On-Site Heavy Metal Analyzer With Polymer Lab-on-a-Chips for Continuous Sampling and Monitoring

An on-site analyzer system for monitoring of heavy metals has been presented. This analyzer can automatically perform long-term continuous water sampling and on-site heavy metals measurement using an array of disposable polymer lab-on-a-chips (lab chip) and a continuous flow sensing method. The system consists of a plastic fluidic motherboard with a microchannels network, microvalves and pump, control circuits, a wireless communication module, a potentiostat, LabVIEW control, and seven disposable heavy metal lab chips. Square wave anodic stripping voltammetry was performed using a microfabricated planar bismuth electrode on the chip for detecting heavy metal (e.g., cadmium, Cd) concentrations. Sensing performance sensitivity was improved with by the continuous flow sensing method propelled by the analyzer. On-site measurement of the Cd concentration change of the soil pore and ground water samples from a lab-scale reactor was automatically performed to evaluate the performance of the analyzer with lab chips.

Kinetics determination of electrogenerated hydrogen peroxide (H2O2) using carbon fiber microelectrode in electroenzymatic degradation of phenolic compounds.

The kinetics of electrogenerated hydrogen peroxide (H(2)O(2)), which can activate peroxidases in an electroenzymatic process, was examined by an amperometric technique using a carbon fiber microelectrode that was modified by polyaniline (PAn) film and platinum particles. The electrogeneration of H(2)O(2) was found to be dependent on the pH and applied potential, and resulting in a variable current response of the carbon fiber microelectrode. The highest amount of H(2)O(2) was electrogenerated when 2.3 V was applied between the Pt/Ti anode and a reticulated vitreous carbon (RVC) cathode at pH 6.0, with a current response of 0.0190 microA min(-1). Phenol was completely degraded by the electroenzymatic reaction of the immobilized horseradish peroxidase (HRP), and the time required for the electrogeneration of H(2)O(2) increased according to the initial concentration of phenol. The degradation stoichiometric ratio between the electrogenerated H(2)O(2) and the aqueous phenol under HRP immobilized on RVC was found to be 1:1.

Advances in pathogen-associated molecules detection using Aptamer based biosensors

Pathogens are all around us in the environment and although advances in medical science have been made to protect against infection by pathogens, through the use of antibiotics, vaccination and fungicide, yet pathogens continue to threaten human life. The fast pathogen detection still remains an unresolved issue since conventional identification and detection methods are complex, costly and require minimum two to three days for detection. Thus there is an urgent need for the development of robust, sensitive and portable diagnostic tools that can lead to accurate and rapid detection of a variety of pathogens. Aptamers are small DNA and RNA oligonucleotides that can bind with high affinity and selectivity to a large number of targets like small and macromolecules from organic, inorganic and biological origin. Aptasensors are biosensors where aptamers are used in place of biological ligands to sense targeted analytes. Oligonucleotide-(both DNA, RNA), peptide- and peptidenucleic acid (PNA)-based aptasensors offer high reproducibility against a wide variety of targets (proteins, peptides, drugs, metabolites, metal ions, cells etc.) and are emerging as the most suitable candidates for analytical methods that use a very small amount (nano to microlitre) of analytes. Herein, the recent developments of aptasensors for the detection of pathogens have been discussed briefly.