posted on 2020-03-06, 09:29authored byGuoqiang Han, Ning Xu, Xieping Sun, Jinzhao Chen, Chun Chen, Qing Wang
As one of the branched-chain amino
acids, l-valine is
an essential nutrient for most mammalian species. In this study, the l-valine producer Corynebacterium glutamicum ΔppcΔaceEΔalatΔpqo was
first constructed. Additionally, an improved biosensor based on the
Lrp-type transcriptional regulator and temperature-sensitive replication
was built. Then, the C. glutamicum strain
was mutagenized by atmospheric and room temperature plasma. A sequential
three-step procedure was carried out to screen l-valine-producing
strains, including the fluorescence-activated cell sorting (FACS),
96-well plate screening, and flask fermentation. The final mutant
HL2-7 obtained by screening produced 3.20 g/L of l-valine,
which was 21.47% higher than the titer produced by the starting strain.
This study demonstrates that the l-valine-producing mutants
can be successfully isolated based on the Lrp sensor system in combination
with FACS screening after random mutagenesis.