Fitness of chassis cells and metabolic pathways for L-cysteine
overproduction in Escherichia coli
Abstract
L-cysteine is a ubiquitous and unique sulfur-containing amino acid with
important physiological functions. The efficient L-cysteine production
via microbial fermentation is interesting and has been paid great
attention. In this study, different Escherichia coli K-12 strains
(JM109, BW25113, MG1655, W3110) were investigated on their suitability
to cysteine-producing plasmid pLH03. The enhancement of precursor
synthetic pathway and thiosulfate assimilation pathway resulted in the
good performance of BW25113. The expressions of synthetic pathway genes
were optimized by two constitutive promoters to assess their effects on
L-cysteine production. Main degradation pathway genes were also deleted
coordinately for more efficient production of cysteine. The L-cysteine
production was further increased through the manipulation of sulfur
transcription regulator cysB and sulfur supplement. After the process
optimization in a 1.5 L bioreactor, the final engineered strain
LH2A1M0B△YTS-pLH03 [BW25113Ptrc2-serA-Ptrc1-cysM-
Ptrc-cysB△yhaM△tnaA△sdaA-(pLH03)] accumulated 8.34 g/L of cysteine,
laying a certain foundation for cysteine fermentation industry.