초록
<P><B>Abstract</B></P> <P> <SMALL>L</SMALL>-arginine, a semi essential amino acid, is an important amino acid in food flavoring and pharmaceutical industries. Its production by microbial fermentation is gaining more and more attention. In previous work, we obtained a new <SMALL>L</SMALL>-arginine producing <I>Corynebacterium crenatum</I> (subspecies of <I>Corynebacterium glutamicum</I>) through mutation breeding. In this work, we enhanced <SMALL>L</SMALL>-arginine production through improvement of the intracellular environment. First, two NAD(P)H-dependent H<SUB>2</SUB>O<SUB>2</SUB>-forming flavin reductases Frd181 (encoded by <I>frd1</I> gene) and Frd188 (encoded by <I>frd2</I>) in <I>C. glutamicum</I> were identified for the first time. Next, the roles of Frd181 and Frd188 in <I>C. glutamicum</I> were studied by overexpression and deletion of the encoding genes, and the results showed that the inactivation of Frd181 and Frd188 was beneficial for cell growth and <SMALL>L</SMALL>-arginine production, owing to the decreased H<SUB>2</SUB>O<SUB>2</SUB> synthesis and intracellular reactive oxygen species (ROS) level, and increased intracellular NADH and ATP levels. Then, the ATP level was further increased by deletion of <I>noxA</I> (encoding NADH oxidase) and <I>amn</I> (encoding AMP nucleosidase), and overexpression of <I>pgk</I> (encoding 3-phosphoglycerate kinase) and <I>pyk</I> (encoding pyruvate kinase), and the <SMALL>L</SMALL>-arginine production and yield from glucose were significantly increased. In fed-batch fermentation, the <SMALL>L</SMALL>-arginine production and yield from glucose of the final strain reached 57.3g/L and 0.326g/g, respectively, which were 49.2% and 34.2% higher than those of the parent strain, respectively. ROS and ATP are important elements of the intracellular environment, and <SMALL>L</SMALL>-arginine biosynthesis requires a large amount of ATP. For the first time, we enhanced <SMALL>L</SMALL>-arginine production and yield from glucose through reducing the H<SUB>2</SUB>O<SUB>2</SUB> synthesis and increasing the ATP supply.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Two new H<SUB>2</SUB>O<SUB>2</SUB>-forming flavin reductases from <I>C. glutamicum</I> are identified. </LI> <LI> Inactivation of the flavin reductases facilitates <SMALL>L</SMALL>-arginine production. </LI> <LI> Increasing the ATP supply facilitates <SMALL>L</SMALL>-arginine production. </LI> </UL> </P>