Oxygen Tolerance Domestication of Blautia sp. AUH-JLD56 Enables Efficient Aerobic Bioconversion of Arctigenin to 3'-Demethylarctigenin

Anaerobic bacteria are the dominant group in the animal intestinal microbiota, and most strains cannot grow or proliferate normally upon exposure to air. Blautia sp. AUH-JLD56 (KF374935) is a strictly anaerobic strain previously isolated by our research group from human feces. Under anaerobic conditions, this strain converts arctigenin to 3′-demethylarctigenin (3′-DMAG), reaching a maximum conversion concentration of 3.6 mM. To improve the oxygen tolerance of this wild-type strain, we performed long-term oxygen tolerance domestication and successfully obtained an oxygen-tolerant mutant. Phenotypic analysis showed that the growth of the oxygen-tolerant mutant under aerobic conditions (OD_{600 nm} = 2.37) was slightly lower than that of the wild-type under strictly anaerobic conditions (OD_{600 nm} = 2.82). Compared with the wild-type, the mutant exhibited an accelerated aerobic growth rate and enabled stable conversion of arctigenin. Notably, under aerobic conditions, the mutant achieved a maximum conversion concentration of 8.2 mM, which is significantly higher than the 3.6 mM obtained with the wild-type under anaerobic conditions. This study realizes, for the first time, efficient aerobic bioconversion of arctigenin to 3′-DMAG using an oxygen-tolerant derivative of a strict anaerobe, thereby overcoming the oxygen-dependent limitation of such strains. Our approach provides a new strategy and technical reference for the oxygen tolerance domestication and industrial application of other intestinal strict anaerobes with specific enzymatic functions.