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Characterization of newly isolated Pseudonocardia sp. N23 with high 1,4-dioxane-degrading ability

Yamamoto, Norifumi, Saito, Yuji, Inoue, Daisuke, Sei, Kazunari, Ike, Michihiko
Journal of bioscience and bioengineering 2018 v.125 no.5 pp. 552-558
Pseudonocardia, bacteria, carbon, diethylene glycol, dioxane, energy, enrichment culture, enzymes, gene expression, groundwater, industrial wastewater, pH, phylogeny, ribosomal RNA, sequence analysis, temperature
This study was conducted to elucidate the 1,4-dioxane degradation characteristics of a newly isolated 1,4-dioxane-degrading bacterial strain and evaluate the applicability of the strain to biological 1,4-dioxane removal from wastewater. A bacterial strain (designated strain N23) capable of degrading 1,4-dioxane as the sole carbon and energy source was isolated from an enrichment culture prepared from 1,4-dioxane-contaminated groundwater. Strain N23 was phylogenetically identified as belonging to the genus Pseudonocardia, based on 16S rRNA gene sequencing. 1,4-Dioxane degradation experiments revealed that strain N23 is capable of constitutive 1,4-dioxane degradation. Further, this strain exhibited the highest specific 1,4-dioxane degradation rate of 0.230 mg-1,4-dioxane (mg-protein)−1 h−1 among 1,4-dioxane-degrading bacteria with constitutively expressed degrading enzymes reported to date. In addition, strain N23 was shown to degrade up to 1100 mg L−1 of 1,4-dioxane without significant inhibition, and to maintain a high level of 1,4-dioxane degradation activity under a wide pH (pH 3.8–8.2) and temperature (20–35 °C) range. In particular, the specific 1,4-dioxane degradation rate, even at pH 3.8, was 83% of the highest rate at pH 7.0. In addition, strain N23 was capable of utilizing ethylene glycol and diethylene glycol, which are both considered to be present in 1,4-dioxane-containing industrial wastewater, as the sole carbon source. The present results indicate that strain N23 exhibits the potential for 1,4-dioxane removal from industrial wastewater.