Concurrent Production of alpha- and beta-Carotenes with Different Stoichiometries Displaying Diverse Antioxidative Activities via Lycopene Cyclases-Based Rational System

alpha- and beta-carotenes belong to the most essential carotenoids in the human body and display remarkable pharmacological value for health due to their beneficial antioxidant activities. Distinct high alpha-/beta-carotene stoichiometries have gained increasing attention for their effective preventions of Alzheimer's disease, cardiovascular disease, and cancer. However, it is extremely difficult to obtain alpha-carotene in nature, impeding the accumulations of high alpha-/beta-carotene stoichiometries and excavation of their antioxidant activities. Herein, we developed a dynamically operable strategy based on lycopene cyclases (LCYB and LCYE) for concurrently enriching alpha- and beta-carotenes along with high stoichiometries in E. coli. Membrane-targeted and promoter-centered approaches were firstly implemented to spatially enhance catalytic efficiency and temporally boost expression of TeLCYE to address its low competitivity at the starting stage. Dynamically temperature-dependent regulation of TeLCYE and TeLCYB was then performed to finally achieve alpha-/beta-carotene stoichiometries of 4.71 at 37 ?degrees C, 1.65 at 30 ?degrees C, and 1.06 at 25 ?degrees C, respectively. In the meantime, these alpha-/beta-carotene ratios were confirmed to result in diverse antioxidative activities. According to our knowledge, this is the first time that both the widest range and antioxidant activities of high alpha/beta-carotene stoichiometries were reported in any organism. Our work provides attractive potentials for obtaining natural products with competitivity and a new insight on the protective potentials of alpha-/beta-carotenes with high ratios for health supply.