Fig. 2

Screening of CYP/CPR for betulinic acid production. a Triterpenoid production by 30 strains that coexpressed LUS with CYP or LUS with CYP and CPR (both CYPs and CPRs originated from 5 different sources). b Triterpenoid production by strains that coexpressed LUS and fused CYP with CPR. N indicates that the encoded protein was located at the N-terminus of the fusion protein; C indicates that the encoded protein was located at the C-terminus of the fusion protein. L0 indicates that the two proteins were fused without any linker. L1, L2, L3 and L4 represent four different linkers, with amino acid sequences GGGS, GSG, GGGGS, and EAAAK, respectively. c Triterpenoid production of strains that coexpressed LUS and endoplasmic reticulum (ER)-targeted CYP and CPR. The ER-targeting sequence was fused to the C-terminus of both CYP and CPR. The red block in the first column of the gene forms represents the CYP/CPR module. Asterisk represents the strains used for subsequent optimization