초록
<P>Fatty acids are a promising raw material for substance production because of their highly reduced and anhydrous nature, which can provide higher fermentation yields than sugars. However, they are insoluble in water and are poorly utilized by microbes in industrial fermentation production. We used fatty acids as raw materials for <SMALL>L</SMALL>-lysine fermentation by emulsification and improved the limited fatty acid-utilization ability of <I>Escherichia coli</I>. We obtained a fatty acid-utilizing mutant strain by laboratory evolution and demonstrated that it expressed lower levels of an oxidative-stress marker than wild type. The intracellular hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) concentration of a fatty acid-utilizing wild-type <I>E. coli</I> strain was higher than that of a glucose-utilizing wild-type <I>E. coli</I> strain. The novel mutation <I>rpsA</I><SUP>D210Y</SUP> identified in our fatty acid-utilizing mutant strain enabled us to promote cell growth, fatty-acid utilization, and <SMALL>L</SMALL>-lysine production from fatty acid. Introduction of this <I>rpsA</I><SUP>D210Y</SUP> mutation into a wild-type strain resulted in lower H<SUB>2</SUB>O<SUB>2</SUB> concentrations. The overexpression of superoxide dismutase (<I>sodA</I>) increased intracellular H<SUB>2</SUB>O<SUB>2</SUB> concentrations and inhibited <I>E. coli</I> fatty-acid utilization, whereas overexpression of an oxidative-stress regulator (<I>oxyS</I>) decreased intracellular H<SUB>2</SUB>O<SUB>2</SUB> concentrations and promoted <I>E. coli</I> fatty acid utilization and <SMALL>L</SMALL>-lysine production. Addition of the reactive oxygen species (ROS) scavenger thiourea promoted <SMALL>L</SMALL>-lysine production from fatty acids and decreased intracellular H<SUB>2</SUB>O<SUB>2</SUB> concentrations. Among the ROS generated by fatty-acid β-oxidation, H<SUB>2</SUB>O<SUB>2</SUB> critically affected <I>E. coli</I> growth and <SMALL>L</SMALL>-lysine production. This indicates that the regression of ROS stress promotes fatty acid utilization, which is beneficial for fatty acids used as raw materials in industrial production.</P>