An improved whole‐cell biotransformation system for ( S )‐equol production

( 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.