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Molecules 2018, 23(9), 2102; https://doi.org/10.3390/molecules23092102

Improved l-Leucine Production in Corynebacterium glutamicum by Optimizing the Aminotransferases

The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China
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Academic Editors: Jiantao Guo and Wei Niu
Received: 12 July 2018 / Revised: 17 August 2018 / Accepted: 20 August 2018 / Published: 21 August 2018
(This article belongs to the Special Issue Design in Synthetic Biology)
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Abstract

The production of branched-chain amino acids (BCAAs) is still challenging, therefore we rationally engineered Corynebacterium glutamicum FA-1 to increase the l-leucine production by optimizing the aminotransferases. Based on this, we investigated the effects of the native aminotransferases, i.e., branched-chain amino acid aminotransferase (BCAT; encoded by ilvE) and aspartate aminotransferase (AspB; encoded by aspB) on l-leucine production in C. glutamicum. The strain FA-1△ilvE still exhibited significant growth without leucine addition, while FA-1△ilvEaspB couldn’t, which indicated that AspB also contributes to L-leucine synthesis in vivo and the yield of leucine reached 20.81 ± 0.02 g/L. It is the first time that AspB has been characterized for l-leucine synthesis activity. Subsequently, the aromatic aminotransferase TyrB and the putative aspartate aminotransferases, the aspC, yhdR, ywfG gene products, were cloned, expressed and characterized for leucine synthesis activity in FA-1△ilvEaspB. Only TyrB was able to synthesize l-leucine and the l-leucine production was 18.55 ± 0.42 g/L. The two putative branched-chain aminotransferase genes, ybgE and CaIlvE, were also cloned and expressed. Both genes products function efficiently in BCAAs biosynthesis. This is the first report of a rational modification of aminotransferase activity that improves the l-leucine production through optimizing the aminotransferases. View Full-Text
Keywords: branched-chain amino acid aminotransferase; aspartate aminotransferase; Corynebacterium glutamicum; l-leucine branched-chain amino acid aminotransferase; aspartate aminotransferase; Corynebacterium glutamicum; l-leucine
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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Feng, L.-Y.; Xu, J.-Z.; Zhang, W.-G. Improved l-Leucine Production in Corynebacterium glutamicum by Optimizing the Aminotransferases. Molecules 2018, 23, 2102.

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