초록
<P>Our study aimed to produce the commercially promising platform chemical 3-hydroxypropionic acid (3-HP) via the propionyl-CoA pathway in genetically engineered <I>Escherichia coli</I>. Recombinant <I>E</I>. <I>coli Ec</I>-P overexpressing propionyl-CoA dehydrogenase (PACD, encoded by the <I>pacd</I> gene from <I>Candida rugosa</I>) under the T7 promoter produced 1.33 mM of 3-HP in a shake flask culture supplemented with 0.5% propionate. When propionate CoA-transferase (PCT, encoded by the <I>pct</I> gene from <I>Megasphaera elsdenii</I>) and 3-hydroxypropionyl-CoA dehydratase (HPCD, encoded by the <I>hpcd</I> gene from <I>Chloroflexus aurantiacus</I>) were expressed along with PACD, the 3-HP titer of the resulting <I>E</I>. <I>coli Ec</I>-PPH strain was improved by 6-fold. The effect of the cultivation conditions on the 3-HP yield from propionate in the <I>Ec</I>-PPH strain was also investigated. When cultured at 30°C with 1% glucose in addition to propionate, 3-HP production by <I>Ec</I>-PPH increased 2-fold and 12-fold compared to the cultivation at 37°C (4.23 mM) or without glucose (0.68 mM). Deletion of the <I>ygfH</I> gene encoding propionyl-CoA: succinate CoA-transferase from <I>Ec</I>-PPH (resulting in the strain <I>Ec</I>-<I>△Y</I>-PPH) led to increase of 3-HP production in shake flask experiments (15.04 mM), whereas the strain <I>Ec</I>-<I>△Y</I>-PPH with deletion of the <I>prpC</I> gene (encoding methylcitrate synthase in the methylcitrate cycle) produced 17.76 mM of 3-HP. The strain <I>Ec</I>-<I>△Y-△P</I>-PPH with both <I>ygfH</I> and <I>prpC</I> genes deleted produced 24.14 mM of 3-HP, thus showing an 18-fold increase in the 3-HP titer in compare to the strain <I>Ec</I>-P.</P>