Publications by authors named "Onekyun Choi"
Until now, bacteria able to degrade, 3,3'-iminodipropionitrile (IDPN), a neurotoxin that destroys vestibular hair cells, causing ototoxicity, culminating in irreversible movement disorders, had never been isolated. The aim of this study was to isolate a novel IDPN-biodegrading microorganism and characterize its metabolic pathway. Enrichment was performed by inoculating activated sludge from a wastewater treatment bioreactor that treated IDPN-contaminated wastewater in M9 salt medium, with IDPN as the sole carbon source.
View Article and Find Full Text PDFThe occurrence of harmful algal blooms dominated by toxic cyanobacteria has induced continuous loadings of algal organic matter (AOM) and toxins in drinking water treatment plants. However, the impact of AOM on the active biofilms and microbial community structures of biologically-active filtration (BAF), which directly affects the contaminant removal, is not well understood. In this study, we systematically examined the effects of AOM on BAF performance and bacterial biofilm formation over 240 days, tracing the removal of specific AOM components, a cyanotoxin [microcystin-LR (MC-LR)], and microbial community responses.
View Article and Find Full Text PDFIn this study, detailed chemical compositions of the biomolecules in extracellular polymeric substances (EPS) from both pure cultures of bacteria and mixed species biofilm isolated from a water utility were analyzed. Then, based on detailed EPS analysis results, the DBP yield experiments were conducted with both extracted EPS and surrogate chemicals to indirectly identify the influence of biomolecules and their structures on DBP formation and speciation. DBP yield results of both extracted EPS and EPS surrogates indicated that proteins in EPS have a greater influence on DBP formation, especially on the formation of nitrogenous DBPs (N-DBPs), where amino acids containing unsaturated organic carbon or conjugated bonds in R-group produced higher amount of DBPs.
View Article and Find Full Text PDFArticle Synopsis
- Researchers accomplished simultaneous separation of 15 racemic aromatic amino acids and L-mimosine through two modified capillary electrophoresis (CE) techniques using different cyclodextrins (CDs) as selectors.
- Hydroxypropyl (HP)-alpha-CD provided good chiral environments for most amino acids, while highly sulfated (HS)-gamma-CD achieved high-resolution separations for nearly all enantiomers except for L-mimosine.
- The methods showed high precision and adequate linearity for chiral assays, enabling detection of nonprotein amino acids from plant seeds, such as L-mimosine and L-3,4-dihydroxyphenylalanine.
Article Synopsis
- A new capillary electrophoresis (CE) system was developed that combines two techniques, capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC), to analyze 23 nonprotein amino acids and 4 protein amino acids.
- The system uses uncoated silica capillary methods under specific buffer conditions for each technique, resulting in different migration patterns for the amino acids.
- The method shows good repeatability and detection limits, successfully identifying amino acids in plant seeds, including mimosine and 2-phenylglycine, alongside known aromatic amino acids like tryptophan and phenylalanine.