Endophytic bacteria and fungi for high production of taxanes: screening and application in the fermentation of Taxus media

Abstract:

[Background] Taxus media are abundant in endophytic bacteria and fungi, which can produce a range of anti-tumor active compounds. Fermentation and processing can increase the concentrations of active components in Chinese herbal medicines. [Objective] To select the optimal strain from the taxane-producing endophytic strains of T. media for solid fermentation and optimize the fermentation duration, so as to innovate the solid fermentation method of T. media. [Methods] The plate streaking method was used to isolate the endophytic strains of T. media. HPLC and UPLC-MS were employed to measure taxanes, and the strains with high yields of taxanes were selected. The selected strains were used for solid fermentation of T. media, and the concentrations of seven components were determined by HPLC. Weighted scores were computed to determine the optimal strain for fermentation, and the optimal duration of the solid fermentation process was determined. The optimal strain was identified by 16S rRNA gene and whole-genome sequencing. [Results] A total of 30 fungal strains and 35 bacterial strains were isolated from T. media, and 7 strains had the ability to produce taxanes. Among them, 6, 4, and 2 strains produced baccatin III, cephalomannine, and taxol, respectively. The 6 strains producing baccatin III were LY2 (2.99 mg/L), LY9 (4.90 mg/L), LP22 (0.34 mg/L), PJ20 (1.43 mg/L), PJ25 (0.18 mg/L), and PJ30 (0.36 mg/L). The 4 strains yielding cephalomannine were LY2 (4.92 mg/L), LY9 (1.31 mg/L), PP4 (0.66 mg/L), and PJ25 (1.31 mg/L). The 2 strains capable of producing taxol were PP4 (0.70 mg/L) and PJ25 (0.34 mg/L). The HPLC results and weighted scores confirmed that LP22 was the predominant strain for solid fermentation and 48 h was the optimum fermentation period. The strain LP22 was identified as Bacillus amyloliquefaciens by 16S rRNA gene and whole genome sequencing. The full-length genome sequencing data was submitted to NCBI and received the accession number PRJNA1039587. [Conclusion] Certain endophytic strains of T. media have the ability to produce taxanes. The solid fermentation with strain LP22 for 48 h increased the content of taxanes and flavonoids in T. media. The findings provide a basis for further research on the fermentation and processing of T. media.