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( Vu Van Hanh ),( Quyen Ðinh Thi ),( Grosch Rita ),( Nguyen Ngoc Dung ) 한국미생물생명공학회(구 한국산업미생물학회) 2013 한국미생물·생명공학회지 Vol.41 No.1
Rhizoctonia solani and Fusarium oxysporum cause yield losses in numerous economically important crops. To develop a biocontrol agent, cell free extracellular compounds (ECs) of 5 bacterial strains Burkholdria sp. L1, Pseudomonas sp. L4, Pseudomonas chlororaphis VN391, Bacillus subtilis VN21 and Enterobacter sp. VN99 from Vietnamese fields, which reduced levels of R. solani root rot in lettuces and F. oxysporum root rot in tomatoes, were investigated. In a growth chamber, ECs of all antagonists markedly enhanced the biomass of lettuces (10 to 14.1%) and tomatoes (11.38 to 13.88%). In greenhouses, the disease`s severity on both crops treated with ECs of the antagonists was reduced significantly and biomass losses in the plants decreased markedly. The reduction level of R. solani root rot in lettuces was 75, 66.7, 50, and 16.7% by ECs of strains L1, L4, VN21 and VN391, respectively. The biomass of lettuces increased markedly by 29.13%, 21.67%, and 23.4% by ECs of strains L1, L4 and VN21, respectively. Similarly, the reduction levels of F. oxysporum root rot in tomatoes was 76.3, 75, 41.7 and 25% by ECs of strain L1, L4, VN21 and VN391, respectively, and the biomass was significantly enhanced by 14.42, 12.7 and 13%, respectively. The ECs of strain L1 exhibited the most effective bio-control agents to suppress R. solani and F. oxysporum.
( Vu Van Hanh ),( Keun Kim ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.5
Improvement of endoglucanase activity was accomplished by utilizing error-prone rolling circle amplification, supplemented with 1.7 mM MnCl2. This procedure generated random mutations in the Bacillus amyloliquefaciens endoglucanase gene with a frequency of 10 mutations per kilobase. Six mutated endoglucanase genes, recovered from six colonies, possessed endoglucanase activity between 2.50- and 3.12-folds higher than wild type. We sequenced these mutants, and the different mutated sites of nucleotides were identified. The mutated endoglucanase sequences had five mutated amino acids: A15T, P24A, P26Q, G27A, and E289V. Among these five substitutions, E289V was determined to be responsible for the improved enzyme activity. This observation was confirmed with site-directed mutagenesis; the introduction of only one mutation (E289V) in the wild-type endoglucanase gene resulted in a 7.93-fold (5.55 U/mg protein) increase in its enzymatic activity compared with that (0.7 U/mg protein) of wild type.
Van Hanh Vu,Suk Il Hong,Keun Kim The Korean Society of Mycology 2008 Mycobiology Vol.36 No.3
The production of aerial conidia of Lecanicillium lecanii 41185, a highly virulent fungus, by solid-state fermentation was studied for use as a biocontrol agent against aphids. Among several agro-industrial solid media, steamed polished rice was found to produce the highest amount of aerial conidia. The optimal conditions for aerial conidia production were determined to be a 28.5% moisture content in the rice, 25℃ culture temperature, rice pH of 6.0, 75% ambient relative humidity, 4-dold seeding culture, 0.6% KNO3, and 12 d of culture time. The conidia yield increased from 5.7×10(9) conidia/g polished rice to 18.2×10(9) conidia/g polished rice following application of these optimized conditions.
Improvement of Fungal Cellulase Production by Mutation and Optimization of Solid State Fermentation
Van Hanh Vu,Tuan Anh Pham,Keun Kim The Korean Society of Mycology 2011 Mycobiology Vol.39 No.1
Spores of Aspergillus sp. SU14 were treated repeatedly and sequentially with Co60 γ-rays, ultraviolet irradiation, and N-methyl-N`-nitro-N-nitrosoguanidine. One selected mutant strain, Aspergillus sp. SU14-M15, produced cellulase in a yield 2.2-fold exceeding that of the wild type. Optimal conditions for the production of cellulase by the mutant fungal strain using solid-state fermentation were examined. The medium consisted of wheat-bran supplemented with 1% (w/w) urea or NH4Cl, 1% (w/w) rice starch, 2.5mM MgCl2, and 0.05% (v/w) Tween 80. Optimal moisture content and initial pH was 50% (v/w) and 3.5, respectively, and optimal aeration area was 3/100 (inoculated wheat bran/container). The medium was inoculated with 25% 48 hr seeding culture and fermented at 35oC for 3 days. The resulting cellulase yield was 8.5-fold more than that of the wild type strain grown on the basal wheat bran medium.