Isolation and characterization of novel 3,3'-iminodipropionitrile biodegrading Paracoccus communis, from an industrial wastewater treatment bioreactor.

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. A bacterial strain with a spherical morphology that could grow at high concentrations was isolated on a solid medium. Growth of the isolated strain followed the Monod kinetic model. Based on the 16S rRNA gene, the isolate was Paracoccus communis. Whole-genome sequencing revealed that the isolated P. communis possessed the expected full metabolic pathway for IDPN biodegradation. Transcriptome analyses confirmed the overexpression of the gene encoding hydantoinase/oxoprolinase during the exponential growth phase under IDPN-fed conditions, suggesting that the enzyme involved in cleaving the imine bond of IDPN may promote IDPN biodegradation. Additionally, the newly discovered P. communis isolate seems to metabolize IDPN through cleavage of the imine bond in IDPN via nitrilase, nitrile hydratase, and amidase reactions. Overall, this study lays the foundation for the application of IDPN-metabolizing bacteria in the remediation of IDPN-contaminated environments.

Relative contribution of biomolecules in bacterial extracellular polymeric substances to disinfection byproduct formation.

In 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. For regulated DBPs, HAA yields were higher than THM yields, while haloacetonitriles were the dominant DBP species formed among unregulated DBPs. However, DBP yields of polysaccharide monomers were lower than those of tested amino acids groups and the DBP yields of polysaccharide monomers were not significantly influenced by their structures. Considering the results obtained in this study, biofilm needs to be considered an important precursor to DBP formation and biofilm eradication methods for water distribution systems need to be carefully selected to minimize subsequent DBP formation.

Impact of algal organic matter on the performance, cyanotoxin removal, and biofilms of biologically-active filtration systems.

The 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. The component analysis (excitation and emission matrix analysis) results for AOM revealed that terrestrial humic-like substances showed the highest removal among all the identified components and were strongly correlated to MC-LR removal. In addition, reduced empty bed contact time and deactivation of biofilms significantly decreased BAF performances for both AOM and MC-LR. The active biofilm, bacterial community structure, and mlrA gene (involved in microcystin degradation) abundance demonstrated that bacterial biofilm composition responded to AOM and MC-LR, in which Rhodocyclaceae, Saprospiraceae, and Comamonadaceae were dominant. In addition, MC-LR biodegradation appeared to be more active at the top than at the bottom layer in BAF. Overall, this study provides deeper insights into the role of biofilms and filter operation on the fate of AOM and MC-LR in BAF.

Profiling and screening analysis of 27 aromatic amino acids by capillary electrophoresis in dual modes.

An efficient capillary electrophoretic (CE) profiling and screening system based on dual modes of capillary zone electrophoresis (CZE) and micellar electrokinetic capillary chromatography (MEKC) was developed for the simultaneous determination of 23 nonprotein amino acids (NPAAs) and 4 protein amino acids with aromatic moiety. It involves separation by an uncoated fused-silica capillary under phosphoric acid buffer in CZE mode and by another uncoated fused-silica capillary under neutral sodium dihydrogen phosphate buffer containing sodium dodecyl sulfate in MEKC mode. Migration orders of the amino acids studied on the two separation modes under each optimum condition were very different. The repeatability of migration times measured by the CZE and MEKC was found to be better than 4.8 and 3.4%, respectively, thereby enabling to cross-check the identification of each amino acid. The method linearity and limit of detection of the CZE for each amino acid were found to be adequate for the assay of aromatic amino acids. When the present CE profiling and screening analysis in dual modes was applied to plant seeds, NPAAs such as mimosine from Mimosa pudica Linné, and 2-phenylglycine from Lindera erythrocarpa Makino were positively detected along with tryptophan, phenylalanine and tyrosine.

Enantioseparation of chiral aromatic amino acids by capillary electrophoresis in neutral and charged cyclodextrin selector modes.

Simultaneous enantioseparations of 15 racemic aromatic amino acids and L-mimosine for their chiral discrimination were achieved by neutral selector-modified capillary electrophoresis (CE) and by charged selector-modified CE. Among the diverse cyclodextrins (CDs) examined, hydroxypropyl (HP)-alpha-CD as the neutral selector and highly sulfated (HS)-gamma-CD as the charged selector provided best chiral environments of different enantioselectivities. Fairly good enantiomeric resolutions were achieved with the HP-alpha-CD mode except for racemic 6-hydroxy-3,4-dihydroxyphenylalanine, threo-3,4-dihydroxyphenylserine and homophenylalanine while high-resolution separations of all the enantiomeric pairs were achieved in the HS-gamma-CD mode except that L-mimosine was not detected and a partial resolution (0.6) for threo-3,4-dihydroxyphenylserine enantiomers. Relative migration times to that of internal standard under the respective optimum conditions were characteristic of each enantiomer with good precision (% RSD: 0.7-3.8), thereby enabling to cross-check the chemical identification of aromatic amino acids and also their chiralities. The method linearity was found to be adequate (r> 0.99) for the chiral assay of the aromatic amino acids investigated. When applied to extracts of three plant seeds, nonprotein amino acids such as L-mimosine (42 nug/g) from Mimosa pudica Linné, and L-3,4-dihydroxyphenylalanine (268 nug/g) from Vicia faba were positively detected along with L-tryptophan, L-phenylalanine and L-tyrosine.