• Biotechnology and Bioprocess Engineering:BBE
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• v.1 no.1
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• pp.41-45
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• 1996

Effects of yeast extract and ammonium sulfate were investigated on the production of L-or-nithine by an arginine auxotroph, Brevibacterium ketoglutamicum in flask and batch cultures. Yeast extract as an arginine source and ammonium sulfate as an inorganic nitrogen source had significant effects on L-ornithine production and cell growth. L-ornithine production was repressed by the excessive addition of arginine. Reversion of auxotrophic cells to the wild type was observed when the initial yeast extract concenfration was too low. There existed optimum concentrations of yeast extract and ammonium sulfate for L-or-nithine production. The effects of yeast extract and ammonium sulfate concentrations of the Leudeking-Piret model parameters were examined to analyze the relationship between cell growth and L-ornithine production.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.81-84
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• 2000

• Journal of Microbiology
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• v.34 no.4
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• pp.316-319
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• 1996

Mycelia of Streptomyces viridochromogenes grown under different pH were analysed for the fatty acid composition. The low relative proportion of 12-methyltetradecanoic acid and the high relative proportion of palmitic acid were characteristic for the young culture under slight acidic pH that caused delay of the aerial mycelium formation. The addition of L-arginine to the culture medium enabled an arginine auxotroph with bald phenotype to have the fatty acid composition similar to that of the wild type and to develop aerial mycelium. The ratio of 12-methyltetradecanoic acid to palmitic acid might be used as a parameter to explain the optimum grwoth in the respect of membrane fluidity.

• Archives of Pharmacal Research
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• v.20 no.5
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• pp.448-453
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• 1997

Protoplast fusion between isoleucine-, argihine- and thymidine-requiring auxotroph $(Ile^{-}, Arg^{-}, Thy^{-})$ of Lentinula edodes and arginine-requiring auxotroph $(Arg^-)$ of Coriolus versicolor has been achieved using 30% polyethylene glycol (M.W.4000) in 10 mM $CaCl_2$-glycine solution (pH 8.0). Fusion hybrids were selected in the 0.6 M sucrose supplemented minimal media on the basis of nutritional complementation with fusion frequency of $7.4{\times}10{-6}$ The hybrids included both parental and non-parental types in colony morphology, growth rate and isozyme patterns. We succeeded inter-order protoplast fusion between the auxotrophs of Lentinula edodes and Coriolus versicolor overcoming the natural barriers of incompatibility. We examined the characteristics of the hybrids and clarified the fusion rocess using electron microscopy.

• Microbiology and Biotechnology Letters
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• v.27 no.4
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• pp.327-332
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• 1999

A highly productive fed-batch fermentation process was developed for the production of L-ornithine by using a new stabilized strain, Breviabcterium ketoglutamicum BK52. Fed-batch cultures with a continuous feeding of the complex medium were conducted on various operating conditions. The optimal concentration of phosphate in the complex medium was 2.1g/L. The optimal feeding rate of L-arginine was 0.028g/L/hr. The optimal feeding point of the complex medium was determined to be at 40 OD of the cell mass. The final L-ornithine concentrations within 64hrs of cultivation in 5 and 50 liter fermenters were 73g/L and 71g/L, respectively. The maximum overall L-ornithine productivity was 1.14g/L/hr which was about 2 times higher than that of the conventional fed-batch culture with intermittent feeding. The overall productivity of the fermentation system is remarkably improved by employing the optimized conditions, and it offers a significant potential for industrial application.

• Journal of Microbiology and Biotechnology
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• v.2 no.2
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• pp.102-107
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• 1992

For the purpose of producing L-ornithine by microbial fermentation, mutant strains were developed from glutamate-producing bacteria by mutagenesis using N-methyl-N'-nitro-N-nitrosoguanidine (NTG) and UV irradiation. Brevibacterium ketoglutamicum BK1046, a L-citrulline auxotroph which is also resistant to arginine hydroxamate (Arghx), was isolated and selected as the best producer of L-ornithine. This strain was capable of producing L-ornithine at a concentration of 24 g/l after 69 hours of cultivation in the 21 jar fermentor. The optimum supplementary level of L-arginine, a substitute for L-citrulline, was found to be about 0.2 g/l in the shake-flask fermentation.

• 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.

• The Microorganisms and Industry
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• v.19 no.2
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• pp.34-41
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• 1993

Industrial strain improvement is concerned with developing or modifying microorganisms used in production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific characteristics such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empirical approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids, organic acids and enzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is a homoserine auxotroph with AEC, TA double metabolic analogue resistant markers. The yield reaches 100 g/l. Besides, the citric acid-producing organism Aspergillus niger, Co827, its productivity reaches the advanced level in the world, is also the result of a series mutations especially with $^60Co{\gamma}$-radiation. The thermostable .alpha.-amylase producing strain A 4041 is the third example. By combining physical and chemical mutations, the strain A 4041 becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The .alpha.-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus niger SP56, its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV-11. Recently, recombinant DNA approach provides a worthwhile alternative strategy to industrial strain improvement. This technique had been used by us to increase the thermostable .alpha.-amylase production and on some genetic researches.

• The Microorganisms and Industry
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• v.15 no.1
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• pp.38-42
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• 1989

Industrial strain Improvement is concerned with developing or modifying microorga-nisms used In production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific cilarafteristic such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empiri-cal approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids. organic acids andenzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is it homoserine auxotroph with AEC, TA double metabolicanalogue resistant markers. The yield reaches 100g/1. Resides, the citric acid-producing organism Aspergillus nuger, Co827, its productivity reches the advanced level in the world, is also the result of a series mutations expecially with Co Y-radiation. The thermostable a-amylaseroducing strain A 4041 is the third example. By combining physical and chemical multations. the strain ,A 4041becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The a-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus nigerSP56 its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV_11. Recently recombinant DNA approach Provides a worth while alternative strategy to Industrial strain improve-ment. This technique had been used by us to increase the thermostable a-amylase production and on some genetic researches.

• Korean Journal of Microbiology
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• v.25 no.1
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• pp.46-51
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• 1987

In order to increase the production of tryptophan by maximizing expression of recombinant trp plasmid, Klebsiella pneumoniae KC 105(pheA tyrA trpE trpR tyrR) was genetically modified. KC 107, inosine monophospate(IMP) auxotroph from KC 105 and KC 108, histidine(His) auxotroph from KC 107 were also derived respectively to increase phosphoribosylpyrophosphate(PRPP) production which is required for tryptophan biosynthesis. From KC 107 phosphoribosylpyrophosphate consumption which is required for tryptophan biosynthesis. From KC 107 and KC 108, KC 109 and KC 110, both arginine auxotrophs were derived respectively. To investigate the expression of recombinant trp plasmid in the selected K. pneumoniae mutants, the auxotrophic mutants were transformed with recombinant trp plasmids pSC 101-$trpE^{FBR}$, pSC 101-trpL(.DELTA.att) $trpE^{FBR}$ (pSC 101-trp-AF). Amount of tryptophan produced and activities of tryptophan synthase of $trpR^{-}$ mutant (KC 100) and $tyrR^{-}$ mutnat(KC 105) containing recombinant plasmid pSC 101-trp operon were increased by 30-40% as compared with KC 99(pheA tyrA trpE) containing recombinant plasmid pSC 101-trp operon. Activities of tryptophan synthase and production of tryptophan of KC 108 ($His^{-}$) and KC 109($Arg^{-}$) containing recombinant plasmid pSC 101-trp operon were increase by two-fold as compared with KC 107 containing pSC 101-trp operon.