Gi-Seok Kwon

Harvesting of Chlorella vulgaris using a bioflocculant from Paenibacillus sp. AM49

Microbial flocculants for harvesting mass cultured Chlorella vulgaris were screened and that from Paenibacillussp. AM49 was identified as the best. The flocculation efficiency of this bioflocculant increased with the pH within a range of pH 5–11 and was 83%, which was higher than the 72% and 78% produced by aluminum sulfate and polyacrylamide, respectively. The highest flocculation efficiency was with 6.8 mm CaCl2 as co-flocculant. The bioflocculant from Paenibacillussp. AM49 can be used effectively to harvest C. vulgaris from large-scale cultures.

Characterization of bioflocculant produced by Bacillus sp. DP-152

A strain (designated DP-152) which produces an excellent flocculating substance was isolated from soil samples and identified as Bacillus species. The major flocculating substance (bioflocculant DP-152) produced by Bacillus sp. DP-152 was purified by ethanol precipitation and cetylpyridinium chloride (CPC) precipitation and gel permeation chromatography. In kaolin suspension, the highest flocculating activity was obtained at the bioflocculant concentration of 1 mg/l. The bioflocculant DP-152, which has an estimated molecular weight of over 2 × 106 daltons, is a novel bioflocculant derived from sugar components consisting of glucose, mannose, galactose, and fucose in an approximate molar ratio of 8 : 4 : 2 : 1. Some of its physico-chemical properties were also determined.

Involvement of oxidative stress in the regulation of H2S production during ultradian metabolic oscillation of Saccharomyces cerevisiae

Periodic evolution of H(2)S during aerobic chemostat culture of Saccharomyces cerevisiae resulted in ultradian metabolic oscillation via periodic inhibition of respiratory activity. To understand the nature of periodic H(2)S evolution, we investigated whether oxidative stress is associated with H(2)S production. The cellular oxidative states represented by intracellular level of lipid peroxides oscillated out of phase with the oscillation of dissolved O(2). Pulse addition of antioxidant, oxidative agent or inhibitor of antioxidation enzymes perturbed metabolic oscillation producing changes in H(2)S evolution. Analysis of H(2)S production profiles during perturbation of oscillation revealed that the amount of H(2)S production is closely linked with cellular oxidative states. Based on these results and our previous reports, we suggest that oxidative stresses result in periodic depletion of glutathione and cysteine, which in turn causes stimulation of the sulfate assimilation pathway and H(2)S production.

Inhibition of DNA topoisomerase I by dihydrotanshinone I, components of a medicinal herb Salvia miltiorrhiza bunge

Dihydrotanshinone I induced topoisomerase I-mediated DNA cleavage in vitro as strongly as camptothecin, but topoisomerase II-mediated DNA cleavage was not affected. In a DNA relaxation assay using calf thymus DNA topoisomerase I and supercoiled pBR322 plasmid DNA, dihydrotanshinone I reduced topoisomerase I-mediated DNA relaxation in a dose-dependent manner. Heat treatment (65°C) of the reaction mixture containing dihydrotanshinone I and topoisomerase I resulted in a substantial reduction in DNA cleavage, suggesting topoisomerase I and dihydrotanshinone I may form a reversible cleavable complex to induce DNA damage. A DNA unwinding assay using T4 DNA ligase showed that dihydrotanshinone I is a very weak DNA intercalator. These results suggest that dihydrotanshinone I inhibits the catalytic activity of topoisomerase I by the formation of a cleavable complex and at least in part through the intercalation into DNA.

Wickerhamomyces ochangensis sp. nov., an ascomycetous yeast isolated from the soil of a potato field.

A novel ascomycetous yeast, designated strain N7a-Y2(T), was isolated from soil collected in a potato field in Ochang, Korea, and its taxonomic position was studied. A neighbour-joining tree based on the D1/D2 domain of large-subunit rRNA gene sequences revealed that the isolate was a member of the Wickerhamomyces clade and that it was closely related to Wickerhamomyces bisporus, Candida quercuum, Candida ulmi and Wickerhamomyces alni. Strain N7a-Y2(T) formed Saturn-shaped ascospores in unconjugated and persistent asci. D1/D2 domain 26S rRNA gene sequence divergences of 11.0-21.1 % between strain N7a-Y2(T) and other members of the Wickerhamomyces clade indicate that the strain represents a novel species of the genus Wickerhamomyces, for which the name Wickerhamomyces ochangensis sp. nov. is proposed. The type strain is N7a-Y2(T) ( = KCTC 17870(T)  = CBS 11843(T)).

GLR1 Plays an Essential Role in the Homeodynamics of Glutathione and the Regulation of H2S Production during Respiratory Oscillation of Saccharomyces cerevisiae

The role of glutathione (GSH) and its homeodynamics during respiratory oscillation of Saccharomyces cerevisiae were investigated. Pulse injection of thiol redox modifying agents, such as diethylmaleate, N-ethylmaleimide, DL-butione-[S,R]-sulfoxamine, or 5-nitro-2-furaldehyde into the culture perturbed oscillation, although the degree of perturbation varied. Analysis of the expression profiles of GSH1 and GLR1, the activities of glutathione reductase, oscillations in cysteine and GSH concentrations, and the chemostat culture of the GLR1 disruptant indicated that GLR1 plays an essential role in the homeodynamics of GSH and the regulation of H2S production.

Isolation and Characterization of Lactobacillus brevis AML15 Producing γ-Aminobutyric acid

For the screening of acid (CABA)-producing bacteria, 86 bacterial strains which produce GABA were isolated from Kimchi and Salted fisk .Among these, three strains designated AML15, AML45-1, AML72 with relatively high GABA productivity were selecled by thin layer chromatography (TLC). To elucidate the relationship between isolated strains and the genus Lactobacillus, their 16S rDNA sequence were examined. The result of their DNA sequences showed 99% similarity with Lactobacillus brevis ATCC 367. On the basis of the these results, isolated strains were identified as Lactobacillus brevis and designated L. brevis AML15. In order to determine the optimum conditions for GABA production, the isolated strains were cultivated in pyridoxal phosphate (PLP) and monosodium glutami. acid (MSG). Results showed that L. brevis AML15 had the highest CABA productivity with 10,424 concentration in MRS broth containing 5% (w/v) MSG and 10 PLP at pH 5.0. The results imply that L. brevis AML15 has the potential to be developed as a strain for GABA hyper-production.

Antioxidant and ACE Inhibiting Activities of Sugared-Buchu (Allium ampeloprasum L. var. porum J. Gay) Fermented with Lactic Acid Bacteria

In recent years, the growing interest in the health care benefits of sugared-plant fermented enzymes has led to increased consumption. This study investigated the fermentation of sugared-buchu (Leek:sugar, 1:3) by lactic acid bacteria (Lactobacillus acidophilus AML 0422, Lactobacillus brevis HLJ 59, Lactobacillus helveticus AML0410, Lactobacillus plantarium KCTC 13093) and the antibacterial activity, antioxidant activity, and functionality (e.g., anti-hypertensive activity) of the fermented product. The fermented sugared-buchu showed high antibacterial activity against Staphylococcus aureus KCTC 1916, at 31.43 mm, and its total polyphenols, total flavonoid content, and DPPH scavenging activity were 160.8-178 mg/ml, 100-108 mg/ml, and 51.4-58.1%, respectively. DPPH scavenging activity was to that of vitamin C (50 ppm). ACE inhibitory activity was 50.4-67%, depending on the strain of lactic acid bacteria, and the control of sugared-buchu activity was higher than 32.6%. These results suggest that sugared-buchu fermented with lactic acid bacteria has strong antibacterial, antioxidant, and ACE inhibitory activities.L. var. porum J. Gay) Fermented with Lactic Acid Bacteria Jung-Bok Lee, Jung-Shik Bae, Il-Kwon Son, Chun-Pyou Jeon, Eun-Ho Lee, Woo-Hong Joo and Gi-Seok Kwon 1 * Department of Bioresource Sciences, Andong National University, Andong 760-749, Korea Wellfine Co., Ltd, 168,Gasan digital 1-ro, Geumcheon-gu, Seoul 153-786, Korea Department of Medicine Quality Analysis, Andong Science College, Andong 760-709, Korea Department of Biology, Changwon National University, Kyungnam 641-713, Korea

Biodegradation of Endosulfan by Klebsiella oxytoca KE-8 Immobilized on Activated Carbon

-1 per day. Moreover, the endosulfan degradation activity could be demonstrated at 4℃ for one month without significant decrease in activity. Results of this study suggest that immobilized cells of Klebsiella oxytoca KE-8 might be applicable to endosulfan contaminated site.

Biological Activities of Ethanol Extracts from Monascus-Fermented Chinese Yam

This study was conducted to investigate antioxidative and physiological activities of ethanol extracts concentration from Monascus-Fermented Chinese Yam (MFCY). The ethanol extracts from MFCY were measured to examine pigment, monacolin K content, total polyphenol content, DPPH radical scavenging activity and angiotensin converting enzyme inhibitory effects. In this study, the results show that Monascus sp. MK2, with Dioscorea batatas Dence. as the substrate, can produce pigments (red, orange, and yellow), monacolin K content, total polyphenol content and DPPH radical scavenging activity at 13.48 (red), 11.66 (orange), 12.77 (yellow), 462.78 (mg/kg), 658.8 (mg/kg) and 92.8% in EtOH extract, respectively. In addition, ACE inhibitory activity was shown to be 74.55% in EtOH extract. Therefore, it can be concluded that Dioscorea batatas Dence is the best fermentative substrate for Monascus species to produce secondary metabolites as biomedicinal substances.