2.1 Strains, media and reagents
All strains used in this study are listed in Table 1. The strains ofMycobacterium were cultured at 30 ℃ and 200 rpm in the MYC/01
seed medium containing glycerol 20 g/L, sodium citrate 2.8 g/L,
NH4Cl 2.7 g/L, K2HPO4⋅3
H2O 0.5 g/L, MgSO4⋅7 H2O
0.5 g/L and ammonium ferric citrate 0.05 g/L for 2 days. Then the seeds
were inoculated with 5% (v/v) into MYC/04 broth containing glucose 25
g/L , sodium citrate 2.8 g/L, corn steep powder 3 g/L,
(NH4)2HPO4 5 g/L, starch
2 g/L, K2HPO4⋅3 H2O 0.5
g/L, MgSO4⋅7 H2O 0.5 g/L, ammonium
ferric citrate 0.05 g/L, PS 0.1 g/L and cultured at 30 ℃ and 200 rpm for
3 days. The initial pH of the medium was adjusted to 8.0.
The reagents described in the media components were purchased from
Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). PS (purity of
95%, the main components are stigmasterol, campesterol, and
β-sitosterol) was obtained from Shanxi Sciphar Natural Products Co.,
Ltd. (Shangluo, China). The 9-OH-AD standard was purchased from Sigma
(Shanghai, China). HP-β-CD was from Zhiyuan Biotechnology Co., Ltd.
(Binzhou, China). The organic solvent was purchased from Bohr Chemical
Reagent Co., Ltd. (Shanghai, China).