• Microbiology and Biotechnology Letters
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• v.15 no.2
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• pp.104-111
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• 1987

As a trial method of breeding L-lysine producing strains, the intraspecific protoplast fusion bet-ween Brevibacterium flavum ATCC 21528R and Brevibacterium flavum ATCC 21529S and the intergeneric protoplast fusion between Brevibacterium flavum ATCC 21528R and Corynebacterium glutamicum ATCC 13058S were performed. The optimum conditions for protoplast formation of these strains were examined and the effect of plasma expander on regeneration and/or fusion was also observed. Both fusants No. CH23 and No. CH4l showed higher productivity of L-lysine than those of parental cells under the optimum cultural conditions at a rate of 21％ and 8.9％, respectively. And, activity of several enzymes in L-lysine biosynthetic pathway including aspartokinase, a rate-limiting enzyme, was determined. Besides, metabolic control mechanism of L-lysine biosynthesis in fusant No. CH23 and in No. CH41 was investigated to compare with that of parental strains.

• Journal of Microbiology and Biotechnology
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• v.21 no.6
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• pp.652-658
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• 2011

The growth kinetics of Streptomyces noursei NRRL 5126 was investigated under different aeration and agitation combinations in a 5.0 l stirred tank fermenter. Poly-${\varepsilon}$-lysine biosynthesis, cell mass formation, and glycerol utilization rates were affected markedly by both aeration and agitation. An agitation speed of 300 rpm and aeration rate at 2.0 vvm supported better yields of 1,622.81 mg/l with highest specific productivity of 15 mg/l.h. Fermentation kinetics performed under different aeration and agitation conditions showed poly- ${\varepsilon}$-lysine fermentation to be a growth-associated production. A constant DO at 40% in the growth phase and 20% in the production phase increased the poly-${\varepsilon}$-lysine yield as well as cell mass to their maximum values of 1,992.35 mg/l and 20.73 g/l, respectively. The oxygen transfer rate (OTR), oxygen utilization rate (OUR), and specific oxygen uptake rates ($qO_2$) in the fermentation broth increased in the growth phase and remained unchanged in the stationary phase.

• Journal of Microbiology and Biotechnology
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• v.7 no.2
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• pp.95-100
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• 1997

• Journal of Microbiology and Biotechnology
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• v.26 no.2
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• pp.226-232
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• 2016

Dihydrodipicolinate reductase is an enzyme that converts dihydrodipicolinate to tetrahydrodipicolinate using an NAD(P)H cofactor in L-lysine biosynthesis. To increase the understanding of the molecular mechanisms of lysine biosynthesis, we determined the crystal structure of dihydrodipicolinate reductase from Corynebacterium glutamicum (CgDapB). CgDapB functions as a tetramer, and each protomer is composed of two domains, an Nterminal domain and a C-terminal domain. The N-terminal domain mainly contributes to nucleotide binding, whereas the C-terminal domain is involved in substrate binding. We elucidated the mode of cofactor binding to CgDapB by determining the crystal structure of the enzyme in complex with NADP⁺ and found that CgDapB utilizes both NADH and NADPH as cofactors. Moreover, we determined the substrate binding mode of the enzyme based on the coordination mode of two sulfate ions in our structure. Compared with Mycobacterium tuberculosis DapB in complex with its cofactor and inhibitor, we propose that the domain movement for active site constitution occurs when both cofactor and substrate bind to the enzyme.

• Microbiology and Biotechnology Letters
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• v.26 no.5
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• pp.387-392
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• 1998

Brevibacterium lactofermentum, a gram-positive bacteria, has both the diaminopimelate (DAP) pathway and meso-DAP-dehydrogenase (DDH) pathway for L-lysine biosynthesis. To investigate importance of DDH pathway and the related ddh gene in lysine production, we introduced site-specific mutagenesis technique. A 300 bp DNA fragment central to the meso-DAP-dehydrogenase gene (ddh) of B. lactofermentum was used to inactive chromosomal ddh gene via homologous recombination. Southern hybridization analysis confirmed that the chromosomal ddh gene was disrupted by the vector sequence. The B. lactofementum ddh mutant obtained have an inactive DDH pathway. The results reveal that inactivation of the ddh gene in B. lactofermentum leads to dramatic reduction of lysine production as well as decrease of the growth rate, indicating that the DDH pathway is essential for high-level lysine production as well as biosynthesis of meso-DAP.

• Korean Chemical Engineering Research
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• v.44 no.1
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• pp.97-105
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• 2006

In order to investigate the effect of inhibitors on L-threonine biosynthesis in Escherichia coli, we have constructed a metabolic network model of amino acid biosynthesis from L-aspartate to L-threonine by using available informations from literatures and databases. In the model, the effects of inhibitors on the biosynthesis of L-threonine was included as an appropriate mathematical form. For simulation study, we used initial values as L-aspartate 5 mM, ATP 5 mM, NADPH 2 mM, and observed the concentration changes of intermediate metabolites over concentration changes of respective inhibitors. As a result, we found that concentrations of intermediate metabolites were not significantly changed over concentration changes of L-lysine, L-methionine, and L-glutamate. But, there were considerable changes of intermediates over concentration changes of L-serine, L-cysteine, and L-threonine, which can be considered as essential effectors on L-threonine synthesis. Contrary, the synthesis of L-threonine seems to be not related to the amounts of L-aspartate, and inversely proportional to the accumulated amount of D,L-aspartic ${\beta}$-semialdehyde.

• Proceedings of the Microbiological Society of Korea Conference
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• 2005.05a
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• pp.204.4-204
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• 2005

• Journal of Microbiology and Biotechnology
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• v.24 no.10
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• pp.1368-1376
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• 2014

This article focuses on the effects of glycine betaine on preventing caramelization, and increasing DCW and $\small{L}$-lysine production. The additional glycine betaine not only decreased the browning intensity (decreased 4 times), and the concentrations of 5-hydroxymethylfurfural (decreased 7.8 times) and furfural (decreased 12 times), but also increased the availability of glucose (increased 17.5%) for $\small{L}$-lysine production. The DCW and $\small{L}$-lysine production were increased by adding no more than 20 mM glycine betaine, whereas the DCW and $\small{L}$-lysine production were decreased with the reduction of pH values, although pH had a better response to prevent caramelization than did glycine betaine. For $\small{L}$-lysine production, the highest increase (40%) was observed on the media with 20 mM glycine betaine. The crucial enzymes in glycolysis and $\small{L}$-lysine biosynthesis pathway were investigated. The results indicated that additional glycine betaine increases the activity of enzymes in glycolysis, in contrast to the effect of pH. All the results indicated that glycine betaine can be used to prevent caramelization and increase the $\small{L}$-lysine production. By applying this strategy, glucose would not be have to be separated from the culture media during autoclaving so that factories can save production costs and shorten the fermentation period.

• Journal of Microbiology and Biotechnology
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• v.25 no.11
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• pp.1819-1826
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• 2015

Poly(ε-ʟ-lysine) (ε-PL) is a novel bioactive polymer secreted by filamentous bacteria. Owing to lack of a genetic system for most ε-PL-producing strains, very little research on enhancing ε-PL biosynthesis by genetic manipulation has been reported. In this study, an effective genetic system was established via intergeneric conjugal transfer for Streptomyces albulus PD-1, a famous ε-PL-producing strain. Using the established genetic system, the Vitreoscilla hemoglobin (VHb) gene was integrated into the chromosome of S. albulus PD-1 to alleviate oxygen limitation and to enhance the biosynthesis of ε-PL in submerged fermentation. Ultimately, the production of ε-PL increased from 22.7 g/l to 34.2 g/l after fed-batch culture in a 5 L bioreactor. Determination of the oxygen uptake rate, transcriptional level of ε-PL synthetase gene, and ATP level unveiled that the expression of VHb in S. albulus PD-1 enhanced ε-PL biosynthesis by improving respiration and ATP supply. To the best of our knowledge, this is the first report on enhancing ε-PL production by chromosomal integration of the VHb gene in an ε-PL-producing strain, and it will open a new avenue for ε-PL production.

• Journal of the Korean Society of Food Science and Nutrition
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• v.30 no.5
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• pp.802-805
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• 2001

The dapD gene of Brevibacterium lactofermentum encoding tetrahydrodipicolinate N-succinyl transferase, one of the enzymes involved in lysine biosynthesis, was cloned by complementation of Escherichia coli dapD mutnat. The recombinant plasmid pLS1 was found to contain a 3.6 kb DNA fragment. Southern hybridization analysis confirmed that the cloned DNA fragment originated from B. lactofermentum. The data of L-lysine production showed that the B. lactofermentum dapD gene was expressed in E. coli.