• Microbiology and Biotechnology Letters
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• v.18 no.4
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• pp.437-441
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• 1990

For the genetic development of more powerful antagonistic Pseudomom - YPL-1 as a biocontxol agent against soilborne plant pathogenic Fuaarium solani causing root rot of many important crops, mutants improving the productivity of chitinase were obtained by mutation with UV radiation or NTG treatment, P. stutzeri YPL-M26 (UV mutant) and P. stutzeri YPL-MI78 (NTG mutant) could improve the productivity of chitinase by 2.5 and 2.0 times, and its antifungal activity by 1.7 and 1.5 times, respectively. The antifungal mechanism of P. stutzeri YPL-M26 was caused by lysis of the fungal cell wall by hydrolytic enzymes such as chitinase. The antifungal activity of crude chitinase of P. stutzeri YPLM26 on the mycelial growth of F. solani was observed to be much higher than that of the original strain. The enzymes produced by P. stutzeri YPL-M26 were the same as the original strain in enzymatic properties such as optimal pH and temperature.

• Journal of Microbiology and Biotechnology
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• v.25 no.12
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• pp.2125-2134
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• 2015

IrrE is a highly conserved global regulator in the Deinococcus genus and contributes to survival from high doses of UV radiation, ionizing radiation, and desiccation. Drad-IrrE and Dgob-IrrE from Deinococcus radiodurans and Deinococcus gobiensis I-0 each share 66% sequence identity. However, Dgob-IrrE showed a stronger protection phenotype against UV radiation than Drad-IrrE in the D. radiodurans irrE-deletion mutant (ΔirrE), which may be due to amino acid residues differences around the DNA-binding HTH domain. Site-directed mutagenesis was used to generate a Drad-IrrE A184S single mutant, which has been characterized and compared with the ΔirrE mutant complemented strain with Drad-irrE, designated ΔirrE-E. The effects of the A184S mutation following UV radiation and mitomycin C (MMC) shock were determined. The A184S mutant displayed significantly increased resistance to UV radiation and MMC shock. The corresponding A184 site in Dgob-IrrE was inversely mutated, generating the S131A mutant, which exhibited a loss of resistance against UV radiation, MMC shock, and desiccation. qPCR analysis revealed that critical genes in the DNA repair system, such as recA, pprA, uvrA, and ddrB, were remarkably induced after UV radiation and MMC shock in the ΔirrE-IE and A184S mutants. These data suggested that A184S improves the ability against UV radiation and MMC shock, providing new insights into the modification of IrrE. We speculated that the serine residue may determine the efficiency of DNA binding, leading to the increased expression of IrrE-dependent genes important for protection against DNA damage.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.614-618
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• 1991

Antifungal compound, KRF-001, was produced by Bacillus subtilis subsp. krictiensis isolated from soil. Physico-chemical factors affecting cell growth and bioactivity were examined to improve the production yield. Nutrient composition, temperature, pH and phosphate ion concentration were proved to be important factors for the production of KRF-001. Mutation was performed to select high yielding strains. First, mutation was performed with ultra-violet light, and the second mutation process was conducted by MNNG (N-Methyl-N'-nitro-N-nitrosoguanidine) resulting in three high yielding strains.

• Applied Biological Chemistry
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• v.31 no.4
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• pp.346-350
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• 1988

A mutant for Korean soy sauce which wilt improve the productivity of amylase and protease was obtained through the second mutation of the original strain using UV radiation. The original strain was the NTG treated mutant of the Bacillus sp. producing peculiar flavour which had been isolated from the korean soy sauce. The mutant could improve the productivity of amylase by 58% and that of protease by 41%. The enzyme produced in this way were similar in enzymatic properties such as optimal reaction pH and temperature. The reaction was not deterred by highly densed salt solution of 5 M and the enzyme productivity was not influenced in the concentration of up to 2 M.

• Applied Biological Chemistry
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• v.32 no.2
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• pp.148-153
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• 1989

Several mutants for rapid fermentation of Korean soybean paste which will improve the productivity of amylase and protease was obtained through the second mutation of the original strain using UV radiation. The original strain was the NTG treated mutant of the Bacillus sp. producing peculiar flavour which had been isolated from the Korean soybean paste. A mutant (SSA3-2M1) could improve the productivity of amylase by 4.4 times and that of protease by 3.7 times. Other one (SSA3-2M2) depressed deaminase productivity by 90% in spite of improvement of amylase and protease. The enzymes produced by strains were similar in enzymatic properties such as optimal reaction pH and temperature. The reaction and productivity of enzymes were not influenced in the high concentration of salt.

• The Korean Journal of Mycology
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• v.24 no.2 s.77
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• pp.135-141
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• 1996

Auxotrophs and drug resistant mutants from the mycelia of Lentinus edodes were obtained by UV irradiation at survival rates of $0.024{\sim}2.45%$ and ethidium bromide (EtBr) enrichment after UV irradiation. The mutation rate was 0.40%, and back mutation rate was $4.81{\times}10^{-4}{\sim}8.46{\times}10^{-4}$. Various amino acid-, nucleic acid-, and vitamin-requiring auxotrophs were isolated. The concentrations of several fungicides, antibiotics and amino acid analogues inhibiting the growth of L. edodes were determined. The MIC values for cycloheximide, benomyl, and p-fluorophenylalanine were 2, 2000, and 1000 ug/ml respectively. Five p-fluorophenylalanine-resistant mutants and eight benomyl-resistant mutants were selected by UV irradiation.

• Applied Biological Chemistry
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• v.28 no.2
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• pp.92-97
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• 1985

UV irradiation method was applied to Agrobacterium tumefaciens A 136 to obtain arginine auxotrophic mutant which is applicable as a host of Ti-plasmid. When the bacterial growth was measured at 600 nm, it showed the exponential phase between 7 and 16 hours after 2% inoculation (v/v) in TY medium and the generation time of 4.8 hours. Survival rate of $1{\sim}0.1%$ was reserved when irradiated at the intensity of $800\;{\mu}w/cm^2$ for $30{\sim}50sec$. Fifteen mutants were selected among 5,000 colonies after UV irradiation. Two of them were identified as arginine auxotrophs, three of them as asparagine auxotrophs, ana the other not as arginine, asparagine, glycine nor cysteine auxotrophs.

• Journal of Microbiology and Biotechnology
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• v.11 no.1
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• pp.118-123
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• 2001

The alginate lyase A1-III gene of Sphingomonas species A1 is composed of 1,077 nucleotides, encoding a protein (359 amino acids) with a molecular mass of 40,322 Da. Recombinant A1-III expressed in Escherichia coli exhibited the same full enzymatic activity as native A1-III. In order to identify the critical residue for activity, a site-directed mutation was introduced into the A1-III gene (H192A, His192->Ala). Recombinant A1-III (H192A) exhibited a significant decrease in enzyme activity (one-thirty thousandth of that of A1-III), without any conformational change, as detected by the CD spectra in the far UV region. Also, the chemical modification of wild-type A1-III with methyl 4-nitro benzene sulfonate resulted in a 40% decrease from the initial activity, whereas the same modification of A1-III (H192A) produced no change in the activity. The role of His192 on the catalytic process was also explored based on a model of A1-III docked with mannuronic acid into the active site.

• Microbiology and Biotechnology Letters
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• v.23 no.6
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• pp.647-651
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• 1995

A tylosin-hyperproductive mutant of S. fradiae MNU20 was isolated among 3500 strains obtaincd from either MNNG- or UV-treated Streptomyces fradiae NRRL2702. The composition of optimal medium for tylosin production was formulated as followed as: 4 g soluble starch, 1 g glucose, 1 g corn steep liquor, 7.5 ml soy bean oil, 0.2 g KH$_{2}$PO$_{4}$, 1 g Na$_{2}$S$_{2}$O$_{3}$$\cdot $5H$_{2}$O, 2 g CaCO$_{3}$, 2 g NaCl, 0.001 g CoCl$_{2}$$\cdot $6H$_{2}$O in 1 liter of distilled water. With the optimal medium, S. fradiae MNU20 was able to produce 159 mg tylosin (g biomass)$^{-1}$, indicating that tylosin productivity of Streptomyces fradiae NRRL2702 was increased 14 times higher by mutation. When the effect of valine, succinate, and natural zeolite on tylosin production was investigated by using the optimal medium, these substances essentially enhanced tylosin production and their addition time during culture period appeared to be critical for the increase of tylosin production.

• BMB Reports
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• v.37 no.6
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• pp.676-683
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• 2004

The conformational properties of hydrophobic core variant ubiquitin (Val26 to Ala mutation) in an acidic solution were studied. The intrinsic tryptophan fluorescence emission spectrum, far-UV and near-UV circular dichroic spectra, the fluorescence emission spectrum of 8-anilinonaphthalene-1-sulfonic acid in the presence of V26A ubiquitin, and urea-induced unfolding measurements indicate this variant ubiquitin to be in the partially folded molten globule conformation in solution at pH 2. The folding kinetics from molten globule to the native state was nearly identical to those from the unfolded state to the native state. This observation suggests that the equilibrium molten globule state of hydrophobic core variant ubiquitin is an on-pathway folding intermediate.