• Microbiology and Biotechnology Letters
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• v.41 no.3
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• pp.263-271
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• 2013

A xylanase-producing bacterium was isolated from a soil sample collected in Yongin city, Korea. The strain was aerobic and gram positive, and grew between pH 5.0 and 11.0, forming a yellow-colored colony. The strain was classified as a novel subspecies bacterium of Paenibacillus barcinonensis by 16S rRNA gene sequence similarity, phylogenetic analysis, phenotypic, and biochemical characteristics, and thus named Paenibacillus sp. HX-1. This strain produced extracellular endo-${\beta}$-1,4-xylanase, and the best xylanolytic activity (205.17 unit/ml) was obtained at 96 h in an optimized TNX medium containing 1% (w/v) bacto tryptone, 1% (w/v) NaCl, and 0.7% (w/v) beechwood xylan at pH 7.0, $37^{\circ}C$ and 200 rpm. The endo-${\beta}$-1,4-xylanase produced by the strain HX-1 yielded xylobiose as the end product from beechwood xylan hydrolysis. The enzyme exhibited optimum pH and temperature at pH 7.0 and $45^{\circ}C$, respectively. The remarkable enhancing effect of the TNX medium on xylanase production by HX-1, in spite of its simple formula, may have great advantages for industrial applications of xylanase.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.85-94
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• 2015

RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine) is the most important explosive contaminant, both in concentration and in frequency, at military shooting ranges in which green technologies such as phytoremediation or constructed wetlands are the best option for mitigation of explosive compounds discharge to the environment. A study was conducted with two identical lab-scale plug flow constructed wetlands planted with Amur silver grass to treat water artificially contaminated with 40 mg/L of toxic explosive compound, RDX. The reactor was inoculated with or without RDX degrading mixed culture to evaluate plant-microorganism interactions in RDX removal, transformation products distribution, and kinetic constants. RDX and its metabolites in water, plant, and sediment were analyzed by HPLC to determine mass balance and kinetic constants. After 30 days of operation, the reactor reached steady-state at which more than 99% of RDX was removed with or without the mixed culture inoculation. The major transformation product was TNX (Trinitroso-RDX) that comprised approximately 50% in the mass balance of both reactors. It was also the major compound in the plant root and shoot system. Acute toxicity analysis of the water samples showed more than 30% of toxicity reduction in the effluent than that of influent containing 40 mg/L of RDX. In the Amur silver grass mesocosm seeded with the mixed culture, the specific RDX removal rate, that is 1st order removal rate normalized to plant fresh weight, was estimated to be 0.84 kg⁻¹ day⁻¹ which is 16.7% higher than that in the planted only mesocosm. Therefore, the results of this study proved that Amur silver grass is an effective plant for RDX removal in constructed wetlands and the efficiency can be increased even more when applied with RDX degrading microbial consortia.

• Journal of Soil and Groundwater Environment
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• v.20 no.6
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• pp.62-72
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• 2015

This study investigates the in-situ implementation of bio-regenerated iron mineral catalyst to remove explosive compounds in ground water at a military shooting range in operation. A bio-regenerated iron mineral catalyst was synthesized using lepidocrocite (iron-bearing soil mineral), iron-reducing bacteria Shewanella putrefaciens CN32, and electron mediator (riboflavin) in the culture medium. This catalyst was then injected periodically in the ground to build a redox active zone acting like permeable reactive barrier through injection wells constructed at a live fire military shooting range. Ground water and core soils were sampled periodically for analysis of explosive compounds, mainly RDX and its metabolites, along with toxicity analysis and REDOX potential measurement. Results suggested that a redox active zone was formed in the subsurface in which contaminated ground water flows through. Concentration of RDX as well as toxicity (% inhibition) of ground water decreased in the downstream compared to those in the upstream while concentration of RDX reduction products increased in the downstream.