High-yield production of l-serine from glycerol by engineered Escherichia coli

Abstract

l-Serine is widely used in pharmaceutical, food and cosmetic industries, and the direct fermentation to produce l-serine from cheap carbon sources such as glycerol is greatly desired. The production of l-serine by engineered Escherichia coli from glycerol has not been achieved so far. In this study, E. coli was engineered to efficiently produce l-serine from glycerol. To this end, three l-serine deaminase genes were deleted in turn, and all of the deletions caused the maximal accumulation of l-serine at 0.06 g/L. Furthermore, removal of feedback inhibition by l-serine resulted in a titer of 1.1 g/L. Additionally, adaptive laboratory evolution was employed to improve glycerol utilization in combination with the overexpression of the cysteine/acetyl serine transporter gene eamA, leading to 2.36 g/L l-serine (23.6% of the theoretical yield). In 5-L bioreactor, l-serine titer could reach up to 7.53 g/L from glycerol, demonstrating the potential of the established strain and bioprocess.