초록
<P>As one of the branched-chain amino acids, <SMALL>L</SMALL>-valine is an essential nutrient for most mammalian species. In this study, the <SMALL>L</SMALL>-valine producer <I>Corynebacterium glutamicum</I><I>ΔppcΔaceEΔalatΔpqo</I> was first constructed. Additionally, an improved biosensor based on the Lrp-type transcriptional regulator and temperature-sensitive replication was built. Then, the <I>C. glutamicum</I> strain was mutagenized by atmospheric and room temperature plasma. A sequential three-step procedure was carried out to screen <SMALL>L</SMALL>-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 <SMALL>L</SMALL>-valine, which was 21.47% higher than the titer produced by the starting strain. This study demonstrates that the <SMALL>L</SMALL>-valine-producing mutants can be successfully isolated based on the Lrp sensor system in combination with FACS screening after random mutagenesis.</P><BR>[FIG OMISSION]</BR>