Fig. 4

Effects of overexpressing the flavin-containing monooxygenase on a intracellular FAD level, b NAD⁺ level, c NADH/NAD⁺ ratio, and d H₂O₂ level. All engineered strains were cultivated in fermentation medium containing 4 g/L phytosterols at 30 °C for 144 h and the fermentation culture was collected regularly at 48–120 h to measure intracellular FAD, NAD⁺, NADH and H₂O₂. The data represent the mean ± standard deviation of three measurements