Abstract
(S)-equol, the most active metabolite of the soybean isoflavones in vivo, has exhibited various biological activities and clinical benefits. Existing studies on the heterologous biosynthesis of (S)-equol via the engineered E. coli constructed have been significantly progressed. In the present study, the engineered E. coli was further improved to be more suitable for (S)-equol production. The four enzymes involved in the biosynthesis of (S)-equol and another GDH for NADPH regeneration were combined to construct the recombinant E. coli BL21(DE3). The optimal conditions for (S)-equol production were explored, respectively. The yield of equol reached 98.05% with 1 mM substrate daidzein and 4% (wt/vol) glucose. Even when the substrate concentration increased to 1.5 mM, (S)-equol could maintain a high yield of 90.25%. Based on the 100 ml one-pot reaction system, (S)-equol was produced with 223.6 mg/L in 1.5 h. The study presented a more suitable engineered E. coli for the production of (S)-equol.