Biosynthesis of (S)-Equol from Soy Whey by Metabolically Engineered Escherichia coli

Abstract

(S)-Equol is one of the most bioactive metabolites of the isoflavones with immense nutritional and pharmaceutical value. Soy whey is the major liquid byproduct of the soy product processing industries that is rich in nutrients and (S)-equol biosynthetic precursor daidzin. However, it is usually disposed into the sewage, causing high environmental contamination. Herein, we constructed a recombinant Escherichia coli for the biosynthesis of (S)-equol from soy whey. First, we evaluated daidzin-specific transporters and optimized the anaerobically induced P nar in the (S)-equol biosynthesis cassette to produce (S)-equol from daidzin. Then, sucrase and α-galactosidase were co-expressed to confer sucrose, stachyose, and raffinose utilization capacity on E. coli. Meanwhile, EIIBCAglc was inactivated to eliminate the daidzin transport inhibition induced by glucose. Finally, combining these strategies and optimizing the fermentation conditions, the optimal strain produced 91.5 mg/L of (S)-equol with a yield of 0.96 mol/mol substrates in concentrated soy whey. Overall, this new strategy is an attractive route to broaden the applications of soy whey and achieve the eco-friendly production of (S)-equol.

Constructing Protein-Scaffolded Multienzyme Assembly Enhances the Coupling Efficiency of the P450 System for Efficient Daidzein Biosynthesis from (2S)-Naringenin

“…Notably, strain S6 showed higher daidzein production than strain S5 when 200 mg/L (2 S )-naringenin was added to the cultures, which was consistent with the results of enzymatic activities observed in vitro (Figures C,D and B). Optimizing substrate concentration is a commonly employed strategy for enhancing production titer, reducing costs, and improving the competitiveness of microbial conversion processes . Based on the results presented in Figure D, with the increase in the concentration of (2 S )-naringenin from 200 to 400 mg/L, a first increase and then decrease trend in daidzein titer was observed.…”

“…Optimizing substrate concentration is a commonly employed strategy for enhancing production titer, reducing costs, and improving the competitiveness of microbial conversion processes. 35 Based on the results presented in Figure 6D, with the increase in the concentration of (2S)naringenin from 200 to 400 mg/L, a first increase and then decrease trend in daidzein titer was observed. The highest yield of 240.5 mg/L daidzein with a conversion rate of 86% was achieved when 300 mg/L (2S)-naringenin was added to the medium, representing a 9-fold increase compared to strain S5 (Figure 6D).…”

“…The mobile phase was set to 5 mM H 2 SO 4 and the flow rate was set to 0.6 mL/min. The CHIRALPAK-IC column from Daicel Chemical Industries (4.6 mm × 150 mm, 5 μm) was employed for chiral analysis with an isocratic mobile phase of 1 mL/min (hexane/ethanol = 70:30) …”

Deciphering the Crucial Roles of the Quorum-Sensing Transcription Factor SdiA in NADPH Metabolism and (S)-Equol Production in Escherichia coli Nissle 1917

“…( S )-equol is a gut microbial metabolite of daidzein and daidzin, which are the major isoflavones in soybean, and it exhibits heightened antioxidative and estrogenic activities compared with its precursors [ 1 , 2 ]. Its potential in alleviating oxidative stress, menopausal syndrome, cardiovascular disease, and osteoporosis, as well as reducing the risk of prostate, colon, and breast cancer, has garnered substantial clinical interest [ 2 , 3 ]. However, only a fraction (25 to 50%) of people harbor gut bacteria with an ( S )-equol-producing pathway capable of metabolizing dietary daidzein into ( S )-equol [ 4 , 5 ].…”

“…Fecal transplant therapy has demonstrated success in conferring an ( S )-equol-producing phenotype in hosts by providing them with exogenous gut bacteria expressing the necessary enzymes for daidzein conversion into ( S )-equol [ 6 , 7 ]. Recently, engineered bacteria-integrated ( S )-equol-producing pathways have been utilized as efficient whole-cell biocatalysts for ( S )-equol production [ 3 , 8 ]. Given that EcN is a probiotic widely used as a host for the development of engineered probiotics [ 9 , 10 ], it can be used to develop an engineered probiotic with the capability of converting dietary isoflavones into ( S )-equol efficiently [ 11 ].…”