Construction of Escherichia coli strains producing l-serine from glucose

l -Serine is usually produced from glycine. We have genetically engineered Escherichia coli to produce l -serine from glucose intracellularly. d -3-Phosphoglycerate dehydrogenase (PGDH, EC 1.1.1.95) in E. coli catalyzes the first committed step in l -serine formation but is inhibited by l -serine. To overcome this feedback inhibition, both the His 344 and Asn 346 residues of PGDH were converted to alanine and the mutated PGDH (PGDH dr ) became insensitive to l -serine. However, overexpression of PGDH dr gave no significant increase of l -serine accumulation but, when l -serine deaminase genes ( sdaA , sdaB and tdcG ) were deleted, serine accumulated: (1) deletion of sdaA gave up to 0.03 mmol l -serine/g; (2) deletion of both sdaA and sdaB accumulated l -serine up to 0.09 mmol/g; and (3) deletion of sdaA , sdaB and tdcG gave up to 0.13 mmol l -serine/g cell dry wt.