L-Valine Production Using Microbial Auxotroph

Nakayama, Kiyoshi; Kitada, Sohei; Kinoshita, Shukuo

doi:10.2323/jgam.7.52

Cited by 22 publications

(10 citation statements)

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“…This tendency was recognized by present authors at valine accumulation in isoleucine-less and leucine-less mutants (11). This principle was also experienced in lysine accumulation by homoserine-less mutant as shown in Table 4.…”

Section: Change Of Fermentationsupporting

confidence: 77%

Studies on Lysine Fermentation I.

Nakayama¹,

Kitada²,

Kinoshita³

1961

J. Gen. Appl. Microbiol.

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Section: Change Of Fermentationsupporting

confidence: 77%

Studies on Lysine Fermentation I.

Nakayama¹,

Kitada²,

Kinoshita³

1961

J. Gen. Appl. Microbiol.

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“…A third possibility would be a general growth limitation introduced by the L-isoleucine auxotrophy. Several amino acid producer strains have auxotrophies (2,23,37,39), often for an amino acid whose pathway is linked to that of the amino acid synthesized (17). It is therefore difficult to separate regulatory effects from others, such as, for instance, an increased precursor availability.…”

Section: Discussionmentioning

confidence: 99%

“…By undirected mutagenesis, strains of C. glutamicum excreting up to 10 g of L-valine liter Ϫ1 have been obtained (23). A mutant of C. glutamicum subsp.…”

mentioning

confidence: 99%

Linking Central Metabolism with Increased Pathway Flux: l -Valine Accumulation by Corynebacterium glutamicum

Radmacher

Vaitsikova

Burger

et al. 2002

Appl Environ Microbiol

109

104

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Mutants of Corynebacterium glutamicum were made and enzymatically characterized to clone ilvD and ilvE, which encode dihydroxy acid dehydratase and transaminase B, respectively. These genes of the branched-chain amino acid synthesis were overexpressed together with ilvBN (which encodes acetohydroxy acid synthase) and ilvC (which encodes isomeroreductase) in the wild type, which does not excrete L-valine, to result in an accumulation of this amino acid to a concentration of 42 mM. Since L-valine originates from two pyruvate molecules, this illustrates the comparatively easy accessibility of the central metabolite pyruvate. The same genes, ilvBNCD, overexpressed in an ilvA deletion mutant which is unable to synthesize L-isoleucine increased the concentration of this amino acid to 58 mM. A further dramatic increase was obtained when panBC was deleted, making the resulting mutant auxotrophic for D-pantothenate. When the resulting strain, C. glutamicum 13032⌬ilvA⌬panBC with ilvBNCD overexpressed, was grown under limiting conditions it accumulated 91 mM L-valine. This is attributed to a reduced coenzyme A availability and therefore reduced flux of pyruvate via pyruvate dehydrogenase enabling its increased drain-off via the L-valine biosynthesis pathway.

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“…L-valine has been produced by employing bacteria belonging to the genera Brevibacterium, Corynebacterium, and Serratia, which have been improved by random mutation and selection (6,7). A recent report describes the production of L-valine by rationally constructed Corynebacterium glutamicum, in which a feedback inhibition-resistant small subunit of acetohydroxy acid synthase (AHAS; encoded by ilvN) was generated by site-directed mutagenesis; the panB (encoding pantothenate synthase) and ilvA (encoding threonine dehydratase) genes were deleted; and the ilvBNC operon, encoding acetohydroxy acid synthase (ilvBN), and acetohydroxy acid isomeroreductase (ilvC) were overexpressed (8).…”

mentioning

confidence: 99%

Metabolic engineering of Escherichia coli for the production of l -valine based on transcriptome analysis and in silico gene knockout simulation

Park¹,

Lee²,

Kim³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

501

306

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The L-valine production strain of Escherichia coli was constructed by rational metabolic engineering and stepwise improvement based on transcriptome analysis and gene knockout simulation of the in silico genome-scale metabolic network. Feedback inhibition of acetohydroxy acid synthase isoenzyme III by L-valine was removed by site-directed mutagenesis, and the native promoter containing the transcriptional attenuator leader regions of the ilvGMEDA and ilvBN operon was replaced with the tac promoter. The ilvA, leuA, and panB genes were deleted to make more precursors available for L-valine biosynthesis. This engineered Val strain harboring a plasmid overexpressing the ilvBN genes produced 1.31 g/liter L-valine. Comparative transcriptome profiling was performed during batch fermentation of the engineered and control strains. Among the down-regulated genes, the lrp and ygaZH genes, which encode a global regulator Lrp and L-valine exporter, respectively, were overexpressed. Amplification of the lrp, ygaZH, and lrp-ygaZH genes led to the enhanced production of L-valine by 21.6%, 47.1%, and 113%, respectively. Further improvement was achieved by using in silico gene knockout simulation, which identified the aceF, mdh, and pfkA genes as knockout targets. The VAMF strain (Val ⌬aceF ⌬mdh ⌬pfkA) overexpressing the ilvBN, ilvCED, ygaZH, and lrp genes was able to produce 7.55 g/liter L-valine from 20 g/liter glucose in batch culture, resulting in a high yield of 0.378 g of L-valine per gram of glucose. These results suggest that an industrially competitive strain can be efficiently developed by metabolic engineering based on combined rational modification, transcriptome profiling, and systems-level in silico analysis.systems biology ͉ global regulator ͉ exporter ͉ in silico prediction M ost amino acid-producing bacterial strains have been constructed by random mutagenesis. A significant disadvantage of this approach is the possibility that the random distribution of mutations in regions not directly related to amino acid biosynthesis can cause unwanted changes in physiology and growth retardation. Rational metabolic engineering by specific targeted modifications can overcome this disadvantage. The recent development of omics technology, combined with computational analysis, now provides a new avenue for strain improvement (1-4) by providing new information extracted from a large number of data, which is termed ''systems biotechnology'' (5).L-valine, an essential hydrophobic and branched-chain amino acid, is used as a component of cosmetics and pharmaceuticals as well as animal feed additives. L-valine has been produced by employing bacteria belonging to the genera Brevibacterium, Corynebacterium, and Serratia, which have been improved by random mutation and selection (6, 7). A recent report describes the production of L-valine by rationally constructed Corynebacterium glutamicum, in which a feedback inhibition-resistant small subunit of acetohydroxy acid synthase (AHAS; encoded by ilvN) was generated by site-directed mutagen...

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L-Valine Production Using Microbial Auxotroph

Cited by 22 publications

References 1 publication

Studies on Lysine Fermentation I.

Studies on Lysine Fermentation I.

Linking Central Metabolism with Increased Pathway Flux: l -Valine Accumulation by Corynebacterium glutamicum

Metabolic engineering of Escherichia coli for the production of l -valine based on transcriptome analysis and in silico gene knockout simulation

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