• Applied Biological Chemistry
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• 제42권3호
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• pp.188-192
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• 1999

In order to minimize the mycelial pellet formation, one of the critical obstacles during the fermentation processes of filamentous fungi, an investigation was focused on the culture conditions(media and initial inoculum) and additives(soils, surfactants and polyethylene glycol 200) when a high phosphate-dissolving fungus, Penicillium sp. GL-101, was cultured in liquid media. Culturing the strain in PDB, SDB and YPD media, their pellet sizes decreased to the order of YPD > SDB > PDB. And at the high concentrations of the initial inoculum in the range from $1{\times}10^3\;to\;1{\times}10^6$ conidia/ml, the small sizes of pellet were formed in the PDB media. For the initial inoculum between $1{\times}10^7\;and\;1{\times}10^8$ conidia/ml, however, an amorphous pellet or loose aggregate was formed. The addition of soils, zeolite and diatomite, up to 1.0% decreased the pellet sizes to 3/4 and 1/2, respectively, but the pellet was increased to 2.5 times by the addition of bentonite. Surfactants also affected on the size of pellet; the addition of Triton X-100 and Tween 80 up to 1.0% decreased the pellet sizes maximally to 1/10 and 1/4, respectively, while SDS completely inhibited the fungal growth. Among the four additives tsted, polyethylene glycol 200 was the most effectively reduced the pellet sizes to $0.2{\pm}0.1$mm that resulted in about 25- fold reduction compared to the control.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제8권3호
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• pp.627-631
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• 2007

The factors affecting on sludge sedimentation are reported as F/M ratio, ingredient, composition of influent substrate, dissolved oxygen concentration, temperature, pH, filamentous bacteria and SRT. Aeration tank applying Bacillus sp. has an important role for maintaining the dominant microorganism species to make steady progress for spore growth affecting sedimentation. This research aims to investigate the affecting factor for the sedimentation in B3 system and RABC system with aeration tank applying tapered aeration. Extracellular polymeric substances(EPS), protein and carbohydrate can be produced for the extreme condition, that is down to 0.2 mg/L of dissolved oxygen in the aeration tank. This research found out the relation between the sedimentation and the EPS production, especially the ratio of protein/carbohydrate. The spore of Bacillus sp. was formed at the low DO then microorganisms produced EPS. The results showed that the production of EPS was 109.95 mgEPS/gSS at 1.6 mg/L of DO, however it was 131.77 mgEPS/gSS at 0.5 mg/L of DO. The sedimentation was affected by protein content in EPS and the ratio of protein and carbohydrate. The settleability of sludge was not affected by the ratio of protein/carbohydrate in B3 process, meanwhile settleability was affected by the ratio of it in RABC process, respectively.

• Korean Journal of Environmental Agriculture
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• 제36권4호
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• pp.299-305
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• 2017

BACKGROUND: Although the filamentous fungal pathogen Colletotrichum species causing anthracnose disease on various fruits including peach, apple, persimmon and grape, there is no report on Japanese plum in Korea. METHODS AND RESULTS: In 2016, diseased fruits showing typical anthracnose symptoms of Japanese plum were collected in market and ochards. Diseased tissue was cut off and disinfected subsequently with 70% ethanol for 1 min, and in 1% sodium hypochloride solution for 1 min, followed by three washes with sterile distilled water. The disinfected tissues were placed onto potato dextrose agar (PDA), and incubated at $25^{\circ}C$ in the dark for 5 to 7 days. For single-spore isolation, conidia were scraped off the plate using a loop, and suspended with 10 mL sterile distilled water. One hundred microliter of the conidial suspension was spread on PDA plates and incubated at $25^{\circ}C$. Finally, one germinated conidium was transferred onto PDA plates. Morphological and cultural characteries of colonies and spores of isolated Colletotrichum were observed after 7 to 10 days incubation on PDA. Molecular identification of isolates were analyzed by comparing rDNA-ITS gene sequences with NCBI GeneBank. CONCLUSION: Of eleven isolates of Colletotrichum isolated from anthracnose diseased Japanese plum fruits, six were identified as C. acutatum, and five as C. gloeosporioides based on diagnostic characteristics such as colony growth rate, shape and size of conidia, and rDNA-ITS sequences. This is the first report of Colletotrichum causing the anthracnose on Japanese plum in Korea.

• Journal of Life Science
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• 제21권1호
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• pp.96-101
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• 2011

S-Adenosyl-L-methionine synthtase (SAM-s) catalyzes the biosynthesis of SAM from ATP and L-methionine. SAM plays important roles in the primary and secondary metabolism of cells. A metK encoding a SAM-s was searched from Streptomyces natalensis producing natamycin, a predominantly a strong antifungal agent, inhibiting the growth of both yeasts and molds and preventing the formation of aflatoxin in filamentous fungi. To obtain the metK of S. natalensis, PCR using primers designed from the two highly conserved regions for metK genes of Streptomyces strains was carried out, and an intact 1.2-kb metK gene of S. natalensis was cloned by genomic Southern hybridization with PCR product as a probe. To identify the function of the cloned metK gene, it was inserted into pSET152ET for its high expression in the Streptomyces strain, and then introduced into S. lividans TK24 as a host by transconjugation using E. coli ET12567(pUZ8002). The high expression of metK in S. lividans TK24 induced actinorhodin production on R5 solid medium, and its amount in R4 liquid medium was 10-fold higher than that by exconjugant including only pSET152ET.

• Journal of agriculture & life science
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• 제46권3호
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• pp.37-45
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• 2012

To select bacterial strains with antifungal activity against an anthracnose fungal disease causing damage severely on hot pepper, previous isolates obtained from plant root samples were screened. Among 457 isolates, IA70-5 isolate was finally selected and identified as Streptomyces padanus based on 16S rDNA sequence analysis. Strain IA70-5 is non-pigmenteous, non-mobile, and filamentous. S. padanus IA70-5 inhibited effectively the mycelium growth, spore germination, and appressorium formation of Colletotrichum acutatum in vitro. The results of this study demonstrated that IA70-5 strain, especially applied on fruit of hot pepper, decreased disease incidence 90% for pre-inoculation before pathogen treatment. Taken together, S. padanus IA70-5 strain is a promising biological control agent to control of a major fungal pepper disease, anthracnose.

• Korean Journal of Microbiology
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• 제55권3호
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• pp.191-198
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• 2019

H-NS binds to promoter DNA and works as a general transcription silencer. DicA protein, by binding to the promoter DNA of dicA, activates dicA expression and at the same time inhibits expression of dicF and dicB, thus, exerting cell division control in Escherichia coli. H-NS complexed with a nucleoid protein Cnu was known to be involved in dicA expression. However, the exact nature of H-NS binding to dicA promoter DNA and the consequences of H-NS binding in expression of dicA is not clear. In this study, we explored the DNA binding activity of H-NS on the promoter DNA of dicA and found that H-NS binding occurs exclusively to the dicA promoter DNA. We never observed, however, H-NS binding at the vicinity of the dicA promoter. Temperature dependent oligomerization of H-NS was observed during DNA binding and the Cnu protein enhances the oligomerization process of H-NS binding. In vivo measurement of dicA expression in an hns deleted strain showed that dicA expression increased. These results demonstrated that H-NS binds specifically to dicA promoter DNA and functions as a transcription silencer.

• Korean Journal of Microbiology
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• 제55권3호
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• pp.181-190
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• 2019

In Escherichia coli, DicA protein is involved in cell division control. DicA protein is known to bind DNA better at $25^{\circ}C$ than at $37^{\circ}C$. However, the molecular cause of the temperature dependent binding is not clear. In this study, we investigated how DicA binds DNA and why its DNA binding activity depends on temperature. An unique in vivo DNA binding assay developed in this laboratory showed that unlike the homologous proteins such as RovA or SlyA, DicA uses its N-terminal domain for DNA binding. The in vivo DNA binding assay of DicA also demonstrated that the temperature-dependent DNA binding activity does not come from Cnu or H-NS that is known to bind DNA better at $25^{\circ}C$ than at $37^{\circ}C$. Electrophoretic Mobility Shift Assay (EMSA), when performed with purified DicA protein, did not show temperature-dependent DicA binding activity. However when EMSA was performed with crude protein from WT E. coli cells, temperature-dependent DicA binding activity was observed, suggesting that there is a factor(s) that confers temperature DNA binding activity of DicA in vivo.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제11권4호
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• pp.158-164
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• 2006

Yongdam Lake is the fifth largest artificial lake in Korea newly formed by the first impounding the Yongdam Multi-purpose Dam on December, 2002. Yongdam Lake, with her total water storage of 820 million M/T, is located at the roof-top region of the streams flowing into the just-constructed new Saemankeum Lake. Seasonal succession of phytoplakton in Yongdam Lake might affect cyanobacterial blooms in Saemankeum Lake by inoculating seasonal dominants. During 2002-2003 when the first impounding after the construction of Yongdam Multi-purpose Dam was still undergoing, summer cyanobacterial blooms by Anabaena, Microcystis, and Aphanizomenon were observed. Among these three, filamentous Anabaena is well known to have its species with $N_2-fixing$ ability and special cells such as heterocysts and akinetes as well as the vegetative cells. We established a clonal culture of Anabaena spiroides v. crasse (KNU-YD0310) from the live water samples collected at the bloom site of Yongdam Lake. The N- and P-nutrient requirement of the KNU-YD0310 was explored by the experimental cultivation of the laboratory strain. Ratio of heterocysts to vegetative cells increased as N-deficiency extended with its maximum at $N_2-fixing$ condition. The strain KNU-YD0310 exhibited considerable growth under N-limiting conditions while its growth was proportional to the initial phosphate-P concentration under P-deficient conditions. Under P-limiting conditions akinete density increased, which could be interpreted as an adaptation strategy to survive severe environment by transforming into resting stage. The above eco-physiological characteristics of Anabaena spiroides v. crassa might be useful as an ecological criterion in controlling cyanobacterial blooms at Shaemankeum Lake in near future.

• Journal of Life Science
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• 제26권4호
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• pp.460-467
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• 2016

A filamentous cyanobacterium, Limnothrix sp. KNUA012, was axenically isolated from a freshwater bloom sample in Lake Hapcheon, Hapcheon-gun, Gyeongsangnam-do, Korea. Its morphological and molecular characteristics led to identification of the isolate as a member of the genus Limnothrix. Maximal growth was attained when the culture was incubated at 25℃. Analysis of its lipid composition revealed that strain KNUA012 could autotrophically synthesize alkanes, such as pentadecane (C₁₅H₃₂) and heptadecane (C₁₇H₃₆), which can be directly used as fuel without requiring a transesterification step. Two genes involved in alkane biosynthesis－an acyl-acyl carrier protein reductase and an aldehyde decarbonylase－were present in this cyanobacterium. Some common algal biodiesel constituents－myristoleic acid (C_14:1), palmitic acid (C_16:0), and palmitoleic acid (C_16:1)－were produced by strain KNUA012 as its major fatty acids. A proximate analysis showed that the volatile matter content was 86.0% and an ultimate analysis indicated that the higher heating value was 19.8 MJ kg⁻¹. The isolate also autotrophically produced 21.4 mg g⁻¹ phycocyanin－a high-value antioxidant compound. Therefore, Limnothrix sp. KNUA012 appears to show promise for application in cost-effective production of microalga-based biofuels and biomass feedstock over crop plants.

• Korean Journal of Heritage: History & Science
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• 제14권
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• pp.225-250
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• 1981

The investigation of air fungal population in the storages to keep papers and textiles that are designated as important folk life materials or treasures was carried out from Dec. 17 to. 23, 1980. Isolation media was used for malt extract agar with chloramphnicol to prevent bacterial contamination. Isolation and identification of air fungi from the four preserved rooms were Cladosporium cladosporioides, Alternaria chlamydospora, Aspergillus fumigatus, A. versicolor, Eurotium chevalieri, Penicillium charlesii var. rapidum, P. oxalicum. P. viridicatum, Trichoderma viride, Acremomium sp., Mucor sp. and Yeast. It was found that nine species in eight genera was isolated. Among them, underscribed species in Korea was two species ; Eurotium chevalieri and Penicillium visidicatum. The fungal population of four storages was showed to be dominant species such as Cladosporium cladosporioides and the order was Acremonium, Penicillium, Aspergillus, Trichoderma, Alternaria and Eurotium. Eurotium chevalieri was ascomycetous fungi including distinctive ascospores in cleistothecia, the filamentous fungi was directly isolated from the papers and cellulose materials showing to be fourteen species in eight genera. The most species of the fungi isolated was also Cladosporium cladosporioides and the other fungi were found as Acremonium, Penicillium, Aspergillus and Trichoderma. It was confirmed that underscribed fungi were two species ; Mucor racemosus and Penicillium spinulosvm. The effect of four antifungal agents, benzoic acid, sorbic acid, dehydroacetic acid and thymol was also examined on eight species of Aspergillus, Penicillium, Cladosporium. and Tricoderma. this results were shown that more than 0.5% concentration of thymol inhibited the grow of all fungalspecies and other three chemicals appeared various inhibition zones of fungal growth depending in their different concentrations.