Dihydro-β-ionone production by a one-pot enzymatic cascade of a short-chain dehydrogenase NaSDR and enoate reductase AaDBR1.

Dihydro-β-ionone, a high-value compound with distinctive fragrance, is widely utilized in the flavor and fragrance industries. However, its low abundance in plant sources poses a significant challenge to its application through traditional extraction methods. Development of an enzyme cascade reaction with artificial design offers a promising alternative. Herein, a short-chain dehydrogenase NaSDR, was identified from Novosphingobium aromaticivorans DSM 12444, which exhibited a high activity in converting β-ionol to β-ionone. A novel biosynthesis route to produce dihydro-β-ionone from β-ionol was developed, by utilizing alcohol dehydrogenase NaSDR and enoate reductase AaDBR1. Under the optimized conditions (0.29 mg/mL NaSDR, 0.39 mg/mL AaDBR1, 1 mM NADP and 2.5 mM β-ionol at 40 °C for 2 h), a maximum yield (173.11 mg/L) of dihydro-β-ionone was achieved with a molar conversion rate of 35.6 %, which was 2.7-fold higher than that before optimization. Additionally, this cascade reaction achieved self-sufficient NADPH regeneration through the actions of NaSDR and AaDBR1. This study offered a fresh perspective for achieving a green and sustainable synthesis of dihydro-β-ionone and could inspire on another natural products biosynthesis.