Yong-Woong Kim

Isolation and Characterization of Antifungal Substances from Burkholderia sp. Culture Broth

A new antagonistic Burkholderia strain, designated MP-1 and producing antifungal activities against various filamentous plant pathogenic fungi, was isolated from the rhizoshere in the Naju area. Cultural characteristic studies strongly suggested that this strain belongs to the genus Burkholderia. The nucleotide sequence of the 16S rRNA gene (1491 pb) of strain MP-1 exhibited close similarity (99% to 100%) with other Burkholderia 16S rRNA genes. Extraction of fermentation broth of Burkholderia sp. MP-1 and various separations and purification steps led to isolation of four pure active molecules. The chemical structure of these four compounds—named phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid, and 4-hydroxyphenylacetate methyl ester—was established on the basis on their gas chromatography–electron impact–mass spectrometry (GC-EI-MS) and trimethylsilation GC-EI-MS data. The four isolated compounds inhibited filamentous fungal growth on potato dextrose agar medium supplemented with 100 mg/L of phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid and 4-hydroxyphenylacetate methyl ester individually.

Characterization and kinetics of 45 kDa chitosanase from Bacillus sp. P16

An extracellular 45 kDa endochitosanase was purified and characterized from the culture supernatant of Bacillus sp. P16. The purified enzyme showed an optimum pH of 5.5 and optimum temperature of 60°C, and was stable between pH 4.5-10.0 and under 50°C. The K m and V max were measured with a chitosan of a D.A. of 20.2% as 0.52 mg/ml and 7.71×10−6 mol/sec/mg protein, respectively. The enzyme did not degrade chitin, cellulose, or starch. The chitosanase digested partially N-acetylated chitosans, with maximum activity for 15-30% and lesser activity for 0-15% acetylated chitosan. The chitosanase rapidly reduced the viscosity of chitosan solutions at a very early stage of reaction, suggesting the endotype of cleavage in polymeric chitosan chains. The chitosanase hydrolyzed (GlcN)7 in an endo-splitting manner producing a mixture of (GlcN)2-5. Time course studies showed a decrease in the rate of substrate degradation from (GlcN)7 to (GlcN)6 to (GlcN)5, as indicated by the apparent first order rate constants, k 1 values, of 4.98×10−4, 2.3×10−4, and 9.3×10−6 sec−1, respectively. The enzyme hardly catalyzed degradation of chitooligomers smaller than the pentamer.

Cold-storage of mixed inoculum of Glomus intraradices enhances root colonization, phosphorus status and growth of hot pepper

Growth response of hot pepper (Capsicum annuum L.) inoculated with the arbuscular mycorrhizal (AM) fungus, Glomus intraradices Schenck and Smith was evaluated in a greenhouse study. Three treatments in a soil-based medium amended with rock phosphate were: (1) control (CON), (2) inoculation of G. intraradices as a freshly prepared soil mixture of spores, hyphae and colonized roots of Sorghum vulgare (FM), and (3) inoculation of the fungus as cold-stored mixed inoculum (CM). Colonization at 14 weeks after inoculation with CM was 42.5%, but was significantly lower with FM (14.5%). Inoculation with G. intraradices as FM and CM increased growth of pepper, and total phosphorus and nitrogen uptake in shoots and roots compared with the CON treatment. Inoculation with CM resulted in significant increases in plant dry weight and chlorophyll concentration compared to the FM and CON treatments. Acid phosphatase activity in the rhizosphere was generally increased by AM fungal treatments. Highest acid phosphatase activity occurred at 14 weeks after inoculation with CM. Alkaline phosphatase activity in the CM treatment was significantly higher compared to that in CON and FM treatments throughout the growth period. Thus, cold storage of mixed inoculum enhanced colonization and growth-promoting activity of G. intraradices compared to freshly prepared inoculum.

Heavy Metal Contamination in Dusts and Soils in the Yoecheon Heavy Chemical Industrial Complex Area of Yosu City, Korea

ABSTRACT The increase in the number of heavy metal emitting sources such as automobile emissions, factory emissions and industrial wastes has become the main concerns for the environmental scientists. Heavy metal contamination from the sources has been attracted public attention in the vicinity of the YHCIC(Yoecheon Heavy Chemical Industrial Complex), Chonnam, Korea. In order to investigate the degree of heavy metal contamination and to assess the level of As, Cu, Pb and Zn concentrations, road dusts and soils in the studied areas were sampled and analyzed for As, Cu, Pb and Zn. The mean concentrations of As, Cu, Pb and Zn in road dust samples from the YHCIC area are higher than those from the main streets of the Yosu city and soil samples from the studied areas. The highest concentrations of 187 ppm Cu, 266 ppm Pb and 1122 ppm Zn are found in road dusts, however, concentrations of the analyzed elements in soil samples are significantly lower than those in the road dusts. The pollution indices of road dusts in YHCIC area and main streets of the Yosu city are also higher than those of the soils in this study area, and those of road dusts in the vicinity of YHCIC area are relatively higher than those in main streets of the Yosu city. The pollution indices of the dusts tend to be high in the sites of high industrialization indices. Road dusts may be contaminated with various heavy metals from the automobile emissions, tires and the YHCIC or dust with tires from the closed Au-Ag mines at the northern part of study area. However, main contamination source of the road dusts may be automobile emissions and tires, and minor source may be the metals from the YHCIC and the closed Au-Ag mines.