• YAKHAK HOEJI
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• v.34 no.6
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• pp.447-456
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• 1990

Various methods are available for the production of L-threonine. The microbial production of L-threonine has been achieved by breeding L-threonine analog-resistant auxotrophic mutants of various bacteria. The enzymatic production of L-threonine has been demonstrated by use of threonine metabolic enzymes such as threonine deaminase, threonine aldolase, or threonine dehydrogenase complex. Threonine synthesis from glycine and ethanol seems to be catalyzed by the enzymes Methanol dehydrogenase(MDH) and Serine hydroxymethyltransferase(SHMT), which was also found to catalyze the aldol condensation of glycine with acetaldehyde. The improved production of L-threonine has been achieved by amplifying the genes for the L-threonine biosynthetic enzymes using recombinant DNA techniques.

• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.149-153
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• 2004

L-Threonine fermentation process was constructed on batch and fed-batch culture by using Escherichia coli MT201. The production type of L-threonine was observed as growth-associated production in batch culture. In fed-batch culture studying optimal concentration of yeast extract in feeding media, when 600 g/l of glucose and 60 g/l of yeast extract were added in feeding media, 87 g/$\ell$ of L-threonine was produced. To improve cell growth and L-threonine production, the culture of high cell density was performed in fed-batch culture with oxygen enriched air and feeding media containing L-methionine and phosphate. Under the conditions, we could achieve the highest L-threonine production of98 g/$\ell$ at 60 h. The highest productivity of L-threonine was about 3.85 g/$\ell$/h.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.4
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• pp.251-261
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• 1987

This study was attempted to increase the production of L-Threonine by Brevibacterium Flavum ATCC 14067, To select the strain which produce the highest threonine, mutants ere induced by N-methyl-N'-nitro-N-nitrosoguanidine treatment. The composition of media and cultural condition for its overproduction of threonine were also studied. In a threonine producer, strain B-13(Met-) was the strain producing the highest amount of threonige among methionine, lysine and isoleucine auxotrophs. The following results were obtained. 1. The wild strain and B-13(Met-) produced threonine 1.4mg/ml and 4.86mg/ml , respectively. 2. The optimum composition of medium for producing threonine by Brevibacterium Flavum B-13 was glucose 10%, ammonium sulfate 4%, potassium phosphate monobasic 0.2%, magnesium sulfate 0.05%, biotin $200{\mu}l$, thiamine $300{\mu}l$. Addition of nicotinic acid also led to increase L-threonine production. 3. In addition of organic nutrients to the fermentation medium, peptone n'ere effective and addition of methionine $100{\mu}g/ml$ produced the highest amount of L-Threonine. Aspartic acid and homoserine were also effective when these amino acid were added to the fermentstion medium. 4. Cultural conditon on threonine production by B-16 were investigated. The optimum pH was 7.0-8.0. The highest amount of threnine was produced after 4 days of cultural period.

• Journal of Life Science
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• v.14 no.5
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• pp.868-873
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• 2004

The efficient fermentative production of L-threonine fermentation was achieved by using Escherichia coli MT201, transformed a plasmid carrying pyruvate carboxylase gene. It is an attempt to supply oxaloacetate to the L-threonine biosynthetic pathway. In order to improve the L-threonine productivity of E. coli MT201, a plasmid pPYC which is an expression vector of the pyruvate carboxylase gene of Coryne-bacterium glutamicum, was introduced. When E. coli MT/pPYC was incubated with medium containing only glucose as a carbon source, both the cell growth and L-threonine production were reduced, compared to the results from fermentation of E. coli MT201. In order to circumvent this effect, we attempted the addition of a mixed carbon source, composed of glucose and sodium citrate at a ratio of 1.5:3.5. It was shown that L-threonine production and cell growth (OD660) with E. coli MT/pPYC reached up to 75.7 g/l and 48, respectively, at incubation for 75 hr under fed-batch fermentation conditions. It is assumed that overproduction of L-threonine by anaplerotic pathway leads unbalance of TCA cycle and sodium citrate might playa role to recover normal TCA cycle.

• Microbiology and Biotechnology Letters
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• v.19 no.6
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• pp.583-587
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• 1991

A threonine overproducer, E. coli TF427, which is resistant to threonine analogue, a-amino-(3-hydroxyvaleric acid (AHV), and requires both methionine and isoleucine was developed by the mutations of E, coli W3110 using N-methyl-Nf-nitro-N-nitrosoguanidine (NTG) and UV. The E. coli TF427 produced 46.5 gll of threonine in a 5-L jar fermentor after 44 hr cultivation. The aspartokinase I of TF427 was not inhibited by threonine, and its synthesis was not repressed by threonine plus isoleucine.

• Journal of Microbiology and Biotechnology
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• v.28 no.2
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• pp.293-297
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• 2018

Controlling the residual glucose concentration is important for improving productivity in $\text\tiny{L}$-threonine fermentation. In this study, we developed a procedure to automatically control the feeding quantity of glucose solution as a function of ammonia-water consumption rate. The feeding ratio ($R_{C/N}$) of glucose and ammonia water was predetermined via a stoichiometric approach, on the basis of glucose-ammonia water consumption rates. In a 5-L fermenter, 102 g/l $\text\tiny{L}$-threonine was obtained using our glucose-ammonia water combined feeding strategy, which was then successfully applied in a 500-L fermenter (89 g/l). Therefore, we conclude that an automatic combination feeding strategy is suitable for improving $\text\tiny{L}$-threonine production.

• KSBB Journal
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• v.22 no.1
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• pp.62-65
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• 2007

New strain development strategy using kinetic models and metabolic control analysis was investigated. In this study, previously reported mathematical models describing the enzyme kinetics of intracellular threonine synthesis were modified for mutant threonine producer Escherichia coli TF5015. Using the modified models, metabolic control analysis was carried out to identify the rate limiting step by evaluating the flux control coefficient on the overall threonine synthesis flux exerted by individual enzymatic reactions. The result suggested the production of threonine could be enhanced most efficiently by increasing aspartate semialdehyde dehydrogenase (asd) activity of this strain. Amplification of asd gene in recombinant strain TF5015 (pCL-$P_{aroF}$-asd) increased the threonine production up to 23%, which is much higher than 14% obtained by amplifying aspartate kinse (thrA), other gene in threonine biosynthesis pathway.

• Applied Biological Chemistry
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• v.41 no.7
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• pp.496-499
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• 1998

For the production of theobromine from caffeine, 5 strains of bacteria capable of producing theobromine were isolated from soil. Among them, the strain CT-017 showed the best ability of producing theobromine, and was partially identified as a Pseudomonas sp. For the production of theobromine, fructose was the most effective carbon source at an optimum concentration of 5 g/l. The most effective nitrogen source was 5 g/l of beef extracts. And 0.02 g/l of $Fe^{2+}$, 1.0 g/l of threonine were effective for the production of theobromine. The optimum temperature and initial pH were $28^{\circ}C$ and 6.5, respectively. After 23 hr cultivation, 7.98 g/l of theobromine was produced from 15 g/l of caffeine which corresponds to a conversion yield of 53.2%.

• Asian-Australasian Journal of Animal Sciences
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• v.28 no.4
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• pp.551-558
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• 2015

This study was carried out to evaluate the dietary threonine requirement by measuring the plasma free threonine and ammonia concentrations in rainbow trout, Oncorhynchus mykiss after dorsal aorta cannulation. A total of 70 fish (average initial weight $506{\pm}8.2g$) were randomly distributed into each of the 14 net cages (5 fish/cage). After 48 hours (h) of feed deprivation, each group was intubated at 1% body weight with one of the seven L-amino acid based diets containing graded levels of threonine (0.42%, 0.72%, 0.92%, 1.12%, 1.32%, 1.52%, or 1.82% of diet, dry matter basis). Blood samples were taken at 0, 5, and 24 h after intubation. Post-prandial plasma free threonine concentrations (PPthr) of fish 5 h after intubation with diets containing 1.32% or more threonine were significantly higher than those of fish intubated with diets containing 1.12% or less threonine (p<0.05). Post-absorptive free threonine concentrations (PAthr) after 24 h of intubation of the fish with diets containing 0.92% or more threonine were significantly higher than those of fish intubated with diets containing 0.72% or less threonine. Post-prandial plasma ammonia concentrations (PPA, 5 h after intubation) were not significantly different among fish intubated with diets containing 1.12% or less threonine, except the PPA of fish intubated with diet containing 0.42% threonine. Broken-line model analyses of PPthr, PAthr, and PPA indicated that the dietary threonine requirement of rainbow trout should be between 0.95% (2.71) and 1.07% (3.06) of diet (% of dietary protein on a dry matter basis).

• Journal of Microbiology and Biotechnology
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• v.2 no.4
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• pp.243-247
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• 1992

The thr operon of Escherichia coli TF427, an $\alpha$-amino-$\beta$-hydroxyvaleric acid (AHV)-resistant threonine overproducer, was cloned in a pBluescriptII $KS^＋$ plasmid by complementation of E. coli mutants. All clones contained a common 8.8 kb HindIII-generated DNA fragment and complemented the thrA, thrB, and thrC mutants by showing that these clones contained the whole thr operon. This thr operon was subcloned in the plasmid vectors pBR322, pUC18, and pECCG117, an E. coli/Corynebacterium glutamicum shuttle vector, to form recombinant plasmids pBTF11, pUTF25 and pGTF18, respectively. The subcloned thr operon was shown to be present in a 6.0 kb insert. A transformant of E. coli TF125 with pBTF11 showed an 8~11 fold higher aspartokinase I activity, and 15~20 fold higher L-threonine production than TF125, an AHV-sensitive methionine auxotroph. Also, it was found that the aspartokinase I activity of E. coli TF125 harboring pBTF11 was not inhibited by threonine and its synthesis was not repressed by threonine plus isoleucine.