Biotechnology and Bioprocess Engineering 2022; 27(2): 262-267  
High Yield Fermentation of L-serine in Recombinant Escherichia coli via Co-localization of SerB and EamA through Protein Scaffold
Kim-Ngan T. Tran, Ashokkumar Kumaravel, Jaehoon Jeong, and Soon Ho Hong
Kim-Ngan T. Tran, Ashokkumar Kumaravel, Jaehoon Jeong, Soon Ho Hong*
Department of Chemical Engineering, University of Ulsan, Ulsan 44610, Korea
Tel: +82-52-259-1293; Fax: +82-52-259-1689
Received: April 1, 2021; Revised: September 16, 2021; Accepted: October 14, 2021; Published online: April 30, 2022.
© The Korean Society for Biotechnology and Bioengineering. All rights reserved.

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
L-serine is a non-essential amino acid which has a wide range of applications and plays an important role as a building block for growing cells. L-serine microbial development is considered a difficult activity due to L-serine's central role in cellular metabolism with 2 main degradation pathways. A novel strategy is needed to overcome the L-serine degradation pathway and low Lserine tolerance of Escherichia coli for efficient L-serine production. A synthetic protein scaffold between SerB and EamA was introduced in this study to physically combine the two enzymes. Through this strategy, the L-serine production is more efficient than in competing pathways. By the introduction of a synthetic protein scaffold without metabolic pathway engineering or addition of glycine, 1.8 g/L of L-serine was produced at pH7 and 37°C. By fermentation, 9.4 g/L of serine was produced at a yield of 0.34 mol/mol glucose. These results suggest that the carbon flux was successfully directed to the L-serine secretion pathway without knocking out a competing pathway or adding expensive glycine.
Keywords: L-serine, synthetic protein scaffold, metabolic engineering, Escherichia coli, fermentation

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