Work

Enhanced l-serine synthesis in Corynebacterium glutamicum by exporter engineering and Bayesian optimization of the medium composition

Year: 2025

Type: article

Abstract: l -serine is a versatile, high value-added amino acid, widely used in food, medicine and cosmetics. However, the low titer of l -serine has limited its industrial production. In this study, a cell factory without plasmid for efficient production of l -serine was constructed based on transport engineering. Firstly, the effects of l -serine exporter SerE overexpression and deletion on the cell growth and l -serine titer were investigated in Corynebacterium glutamicum ( C. glutamicum ) A36, overexpression of s erE using a plasmid led to a 15.1% increase in l -serine titer but also caused a 15.1% decrease in cell growth. Subsequently, to increase the export capacity of SerE, we conducted semi-rational design and bioinformatics analysis, combined with alanine mutation and site-specific saturation mutation. The mutant E277K was obtained and exhibited a 53.2% higher export capacity compared to wild-type SerE, resulting in l -serine titer increased by 39.6%. Structural analysis and molecular dynamics simulations were performed to elucidate the mechanism. The results showed that the mutation shortened the hydrogen bond distance between the exporter and l -serine, enhanced complex stability, and reduced the binding energy. Finally, Bayesian optimization was employed to further improve l -serine titer of the mutant strain C-E277K. Under the optimized conditions, 47.77 g/L l -serine was achieved in a 5-L bioreactor, representing the highest reported titer for C. glutamicum to date. This study provides a basis for the transformation of l -serine export pathway and offers a new strategy for increasing l -serine titer. • A novel method to modify SerE was performed to enhance the export efficiency and l -serine titer. • Bayesian optimization was used to enhance the l -serine titer of the mutant strain C-E277K. • The highest l -serine titer reported to date was achieved by C. glutamicum.

Source: Synthetic and Systems Biotechnology

DOI: 10.1016/j.synbio.2025.04.003