• Journal of Life Science
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• v.23 no.10
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• pp.1192-1198
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• 2013

To improve yeast strains for bioethanol production, yeasts with ethanol tolerance, thermotolerance, and ${\beta}$-1,3-glucanase activity were bred using yeast genome shuffling. Saccharomyces cerevisiae $BY4742{\Delta}exg1$/pAInu-exgA, which has extracellular ${\beta}$-1,3-glucanase activity, and the Aspergillus oryzae and S. cerevisiae YKY020 strains, which exhibit ethanol tolerance and thermotolerance, were fused by yeast protoplast fusion. Following cell fusion, four candidate cells (No. 3, 9, 11, and 12 strains) showing thermotolerance at $40^{\circ}C$ were selected, and their ethanol tolerance (7% ethanol concentration) and ${\beta}$-1,3-glucanase activity were subsequently analyzed. All the phenotypes of the two parent cells were simultaneously expressed in one (No. 11) of the four candidate cells, and this strain was called BYK-F11. The BYK-F11 fused cell showed enhanced cell growth, ethanol tolerance, ${\beta}$-1,3-glucanase activity, and ethanol productivity compared with the $BY4742{\Delta}exg1$/pAInu-exgA and YKY020 strains. The results prove that a new yeast strain with different characters and the same mating type can be easily bred by protoplast fusion of yeasts.

• Journal of Microbiology and Biotechnology
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• v.28 no.1
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• pp.95-104
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• 2018

Biosurfactants or microbial surfactants are surface-active biomolecules that are produced by a variety of microorganisms. Biodegradability and low toxicity have led to the intensification of scientific studies on a wide range of industrial applications for biosurfactants in the field of environmental bioremediation as well as the petroleum industry and enhanced oil recovery. However, the major issues in biosurfactant production are high production cost and low yield. Improving the bioindustrial production processes relies on many strategies, such as the use of cheap raw materials, the optimization of medium-culture conditions, and selecting hyperproducing strains. The present work aims to obtain a mutant with higher biosurfactant production through applying mutagenesis on Bacillus subtilis SPB1 using a combination of UV irradiation and nitrous acid treatment. Following mutagenesis and screening on blood agar and subsequent formation of halos, the mutated strains were examined for emulsifying activity of their culture broth. A mutant designated B. subtilis M2 was selected as it produced biosurfactant at twice higher concentration than the parent strain. The potential of this biosurfactant for industrial uses was shown by studying its stability to environmental stresses such as pH and temperature and its applicability in the oil recovery process. It was practically stable at high temperature and at a wide range of pH, and it recovered above 90% of motor oil adsorbed to a sand sample.

• Korean Journal of Microbiology
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• v.28 no.1
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• pp.47-54
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• 1990

In order to investigate physiological characteristics of fusants by interspecific protoplast fusion of the genus Cellulomonas, protoplasts of Cellulomonas flavigena NCIB 12901 and Cellulomonas bibula NCIB 8142 were fused and cell wall regenerated. To give gene maker, C. bibula was treated with 500 ug/ml NTG for 1 hr and arginine requiring auxotrophic mutants were isolated. Protoplasts of the genus Cellulomonas were obtained by treatment with $600{\mu}{\textrm{g}}$/ml lysozyme, and 0.5M sorbitol was optimal for osmotic stabilizer on protoplast fromation. Protoplast fusion was enhanced by 40% PEG)M.W.6,000) containing 25 mM $CaCl_{2}$ at $30^{\circ}C$ for 30 min and fusion frequency between C. bibula and C. flavigena was $5\times 10^{-4}$. Processes of protoplast formation, cell wall regeneration and protoplast fusion were obsdrved by scanning electron microscope. By comparing enzyme activities of cellulase, exocellobiohydrolase, .betha.-glucosidase of the parent strains of Cellulomonas with those of thier mutants and fusants, fusants with increased enzyme activity were obtained. By the studies on nutritional requirement, antibiotic resistance, cellulolytic enzyme activities, type of peptidoglycan and motility of two mutants and fusants, fusants were proved to be recombinant of both mutant strains.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.325-330
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• 1991

In order to develop yeast strains which can effectively produce ethanol from cellulosic hydrolyzates, protoplast fusion between Candida sp. KM-09-135 and Saccharomyces cweoisiue SM-07 was carried out and obtained the excellent fusant KMS-23. Fusant KMS-23 showed the optimal growth temperature and ethanol productivity at $37^{\circ}C$, and assimilated xylose, cellobiose, maltose and raffinose as fermentative sugars. Cell size of the fusant was about 1.2 times greater than that of KM-09-135 and 1.5 times SM-07. DNA content of fusant was 1.3 times higher than that of SM-07 and similar with KM-09-135. Fusant KMS-23 produced 2.57% (v/v) ethanol from saccharified wheat bran containing 6.44% (w/v) of reducing sugar, which was 1.3 times higher than parent strains under the same conditions.

• Microbiology and Biotechnology Letters
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• v.22 no.5
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• pp.467-476
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• 1994

Lactobacillus casei HY 2782, prophage cured strain was characterized to be stable as much as L casei YIT 9018, parent strain. By southern hybridization, it was confirmed that the temperate phage was incorporated in chromosomal DNA of L. casei YIT 9018 as a prophage. It was also proved that the prophage was cured from chromosomal DNA of L casei HY 2782. The growth rate, lactic acid producing ability, carbohydrates fermentation, and enzymatic activity of L. casei HY 2782 were found to be similar to those of L. casei YIT 9018. When L casei HY 2782 was used as a host, the multiplicity of infection (M.O.I.) of the temperate phage for L. casei HY 2782 was 1.0~5.0. Restriction enzyme analysis of pLC90 plasmid from L. casei HY 2782 was shown that the size was an approximately 68.22 kb. The plasmid profiles, genomic DNA patterns, and cellular fatty acids composition of L. casei HY 2782 were similar to those of L casei YIT 9018. And the major fatty acids composition of these strains were C$_{14;0}$,C$_{16;1}$, C$_{16;0}$, C$_{18;1}$ and C$_{19;cyclo-}$ 10 sets of arbitrary primer in the PCR were screened to find differentiation against two strains of L. casei. Among them, b$_{5}-1/17-1 primer was produced an approximately 1.3 kb DNA band of only L casei YIT 9018. And b$_{5}-2/17-2 primer was produced an approximately 1.0 kb DNA band of only L casei HY 2782.

• YAKHAK HOEJI
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• v.40 no.1
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• pp.102-111
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• 1996

LB10522 is a new parenteral broad spectrum cephalosporin with a catechol moiety at C-7 position of beta-lactam ring. This compound can utilize tonB-dependent iron transp ort system in addition to porin proteins to enter bacterial periplasmic space and access to penicillin-binding proteins (PBPs) which are the lethal targets of ${\beta}$-lactam antibiotics. The chelating activity of LB10522 to metal iron was measured by spectrophotometrically scanning the absorbance from 200 to 900nm. When $FeCl_3$ was added, optical density was increased between 450 and 800nm. LB10522 was more active against gram-negative strains in iron-depleted media than in iron-replete media. This is due to the increased expression of iron transport channels in iron-depleted condition. LB10522 showed a similar activity against E. coli DC2 (permeability mutant) and E. coli DCO (wild type strain) in both iron-depleted and iron-replete media, indicating a minimal permeaility barrier for LB10522 uptake. LB10522 had high affinities to PBP 3 and PBP 1A, 1B of E. coli. By blocking these proteins, LB10522 caused inhibition of cell division and the eventual death of cells. This result was correlated well with the morphological changes in E. coli exposed to LB10522. Although the in vitro MIC of LB10522 against P. aeruginosa 1912E mutant (tonB) was 8-times higher than that of the P. aeruginosa 1912E parent strain, LB10522 showed a similar in vivo protection efficacy against both strains in the mouse systemic infection model. This result suggested that tonB mutant, which requires a high level of iron for normal growth, might have a difficulty in surviving in their host with an iron-limited environment.

• Korean Journal of Food Science and Technology
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• v.46 no.2
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• pp.148-152
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• 2014

A mutant strain of Lactobacillus paracasei (ML-7) was derived by ultraviolet irradiation of the parent L. paracasei LS-2 strain, followed by colony selection on pH 3.5 MRS agar plates, on which L. paracasei LS-2 cannot grow. The L. paracasei ML-7 mutant strain produced an increased amount of organic acids compared to the L. paracasei LS-2 parent strain. Broiler chickens were randomly fed with one of three experimental diets: a basal diet as a control, and basal diets supplemented with 0.3% of the L. paracasei LS-2 and L. paracasei ML-7 strains. When concluding the study, the final body weights of the broilers fed with the supplemented basal diets were found to be significantly higher (1.9% for LS-2 and 6.2% for ML-7) than the control broiler group. Broilers fed with basal diet supplemented with the mutant L. paracasei ML-7 strain showed increased body weight and food intake, compared to broilers fed with the basal diet with or without the parent L. paracasei LS-2 strain.

• Archives of Pharmacal Research
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• v.12 no.4
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• pp.249-253
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• 1989

High producers or blocked mutants of aminoglycoside antibiotic-producing Streptomyces spp. were selected by application of an agar plug method and by culturing individual colonies in broth. The productivities of aminoglycoside antibiotic producing organisms were increased by selection of a high producer from colonies obtained by spreading spores of wild strain, or survived from treatment of a mutagen or from the colonies regenerated from protoplast-formation and cell-wall regenerations. Some mutagen treated colonies lost the ability to produce antibiotics (5-8%). Some A-factor negative and deostreptamine or streptidine negative mutants were obtained by N-methyl-N'-nitro-N-nitrosomethylguanidine (MNNG) treatment. Many of the survivors from the MNNG treatment lost the ability to produce antibiotics. Major colonies produced less amount of antibiotics ; only few survived colonies produced more antibiotics than the parent. Resistance of Streptomyces spp. against the antibiotics produced by itself was also markedly affected by mutagen treatment.

• Korean journal of applied entomology
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• v.38 no.3
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• pp.249-253
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• 1999

To study races of Heterodera glycines in Korea, 21 soil samples were collected from eight provinces in 1995. Four races were found; race 3(48%) was a dominant race flowed by race 5(24%), race 1(19%), and race 6(9%). About 30~40% of H. glycines populations reproduced on Pickett and PI88788, while non reproduced on Peking or PI90763. Development of resistant soybean cultivar targeting to race 5 and 6 of H. glycines using PI90763 and PI88788 as a parent is recommended.

• KSBB Journal
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• v.5 no.3
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• pp.255-261
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• 1990

Cell fusion between complementary mutants isolated from astaxanthin-producing yeast, Phaffia rhodozyma, was carried out to obtain astaxanthin-overproducing strains by protoplast fusion technique. The frequency of protoplast fusion was ranged from 2.3$\times$10-5 to 6.0$\times$10-5, and nuclear fusion in the cells of hybrids was demonstrated by several techniques such as isolation of recombinants after mitotic segregation of parental genetic markers, estimation of DNA content, direct observation of nuclei with nuclear staining, and comparison of survival rate to UV exposure. One of several hybrids, Fl, showed approximately 3-fold increase in astaxanthin content when compared with wild parent.