Monday, May 5, 2008
7-12

Systems-level analysis and engineering of Escherichia coli for the production of L-valine

Jin Hwan Park, Kwang Ho Lee, Tae Yong Kim, Yu-Sin Jang, and Sang Yup Lee. Metabolic and Biomolecular Engineering National Research Laboratory, Department of Chemical and Biomolecular Engineering (BK21 program), BioProcess Engineering Research Center, Center for Systems and Synthetic Biotechnology, Department of BioSystems and Bioinformatics Research Center, Institute for the Biocentury, Korea Advanced Institute of Science and Technology (KAIST), 335 Gwahangno, Yuseong-gu, Daejeon, South Korea

The L-valine producing strain of Escherichia coli was constructed by rational metabolic engineering and stepwise improvement based on transcriptome analysis and in silico gene knock-out simulation. 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 were 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 pKKilvBN, which overexpresses the ilvBN genes, produced 1.31 g/liter L-valine. Comparative transcriptome profiling combined with in silico gene knock-out simulation was used for the enhanced production of L-valine. The VAMF strain (Val DaceF Dmdh DpfkA) harboring pKBRilvBNCED and pTrc184ygaZHlrp was able to produce 7.55 g/liter L-valine from 20 g/liter glucose, resulting in a high yield of 0.378 g L-valine per g glucose. The approaches described here can be a good example of systematically engineering strains for the enhanced production of amino acids. [This work was supported by the Korean Systems Biology Project of the Ministry of Science and Technology (M10309020000-03B5002-00000). Further supports by the LG Chem Chair Professorship and KOSEF through the CUPS are appreciated].

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