Pilot test of biological removal of 1,4-dioxane from a chemical factory wastewater by gel carrier entrapping Afipia sp. strain D1.

A pilot-scale (120 L) bioreactor system using a gel carrier-entrapped pure bacterial strain, Afipia sp. strain D1, capable of degrading 1,4-dioxane as a sole carbon and energy source was constructed and applied to treat real industrial wastewater containing 1,4-dioxane from a chemical factory. Although the wastewater not only contained high concentrations of 1,4-dioxane but also considerable amounts of other organic compounds (73 mg-TOCL(-1) on average), the bioreactor could efficiently remove 1,4-dioxane without significant inhibitory effects. The reactor startup could be completed within approximately 1 month by increasing the 1,4-dioxane loading rate (0.09-0.47 kg-dioxanem(-3)d(-1)) in a stepwise manner. Effective 1,4-dioxane removal was stably maintained for 3 months with an influent 1,4-dioxane of 570-730 mg L(-1), giving an average effluent concentration and removal rate of 3.4 mg L(-1) and 0.46 kg-dioxanem(-3)d(-1), respectively. A 1,4-dioxane loading fluctuation between 0.14 and 0.72 kg-dioxanem(-3)d(-1) did not significantly affect its removal, and more than 99% removal efficiency was constantly maintained. The Monod model could well describe the relationship between the effluent 1,4-dioxane concentration and 1,4-dioxane removal rates of the bioreactors, showing that the half-saturation constant (Ks) was 28 mg L(-1).

Biological wastewater treatment of 1,4-dioxane using polyethylene glycol gel carriers entrapping Afipia sp. D1.

A biological treatment system for 1,4-dioxane-containing wastewater was developed using the bacterium Afipia sp. D1, which can utilize 1,4-dioxane as the sole carbon source. Strain D1 was entrapped in a polyethylene glycol gel carrier to stably maintain it in a bioreactor, and continuous feeding tests were performed to treat model industrial wastewater containing 1,4-dioxane. 1,4-Dioxane removal activity rapidly increased soon after the start of feeding of influent with 400 mg/L 1,4-dioxane, and the volumetric removal rate reached 0.67 kg dioxane/m(3)/d on day 36 by a stepwise increase in loading. The start-up period of the 1,4-dioxane treatment reactor was approximately 1 month, and stable removal performance was subsequently achieved for more than 1 month. The average 1,4-dioxane effluent concentration and 1,4-dioxane removal efficiency were 3.6 mg/L and 99%, respectively, during stable operation. Further 1,4-dioxane degradation activity of the of the gel carrier was characterized in batch experiments with respect to temperature. The optimum temperature for 1,4-dioxane treatment was 31.7°C, and significant removal was observed at a temperature as low as 6.9°C. The apparent activation energy for 1,4-dioxane degradation was estimated to be 47.3 kJ/mol. This is the first report of the development of a 1,4-dioxane biological treatment system using gel entrapment technology.

Transcription switches for protoxylem and metaxylem vessel formation.

Land plants evolved xylem vessels to conduct water and nutrients, and to support the plant. Microarray analysis with a newly established Arabidopsis in vitro xylem vessel element formation system and promoter analysis revealed the possible involvement of some plant-specific NAC-domain transcription factors in xylem formation. VASCULAR-RELATED NAC-DOMAIN6 (VND6) and VND7 can induce transdifferentiation of various cells into metaxylem- and protoxylem-like vessel elements, respectively, in Arabidopsis and poplar. A dominant repression of VND6 and VND7 specifically inhibits metaxylem and protoxylem vessel formation in roots, respectively. These findings suggest that these genes are transcription switches for plant metaxylem and protoxylem vessel formation.

Expression analysis of the NgORF13 promoter during the development of tobacco genetic tumors.

We investigated the expression pattern of the promoter of Nicotiana glauca (Ng) ORF13 in the hybrids between N. glauca and N. langsdorffii harboring the NgORF13-beta-glucuronidase (GUS) chimeric gene. The promoter of NgORF13 of N. glauca had lower activities than the promoter of RiORF13 of Agrobacterium rhizogenes agropine-type root-inducing (Ri) plasmid. However, the localization of GUS activity in the NgORF13 transgenic plants was similar to that in the RiORF13 transgenic plants. The GUS activity of NgORF13-GUS was high in genetic tumors cultured in vitro or developed spontaneously on F1 plants with aging or by wounding. The GUS activity in tumors was observed in bud primordia, vascular bundles and leaves in the buds. While the activity was lower than in tumors, NgORF13-GUS was also expressed in vascular bundles and the parenchymatous tissues in plants regenerated from tumors. Furthermore, the promoter activity of NgORF13 was induced by wounding and activated by exogenous application of methyl jasmonate. During tumorization, NgORF13 was induced at an early stage and showed expression patterns similar to both NgrolB and NgrolC whose expression were investigated by Nagata et al. (1996) Plant Cell Physiol. 37: 489-498. It is thought that Ngrol genes might be involved in the formation of genetic tumors, and, moreover, NgORF13 might work in cooperation with NgrolB and NgrolC.