Enhancement of Palmarumycins C-12 and C-13 Production in Liquid Culture of Endophytic Fungus Berkleasmium sp Dzf12 after Treatments with Metal Ions

The influences of eight metal ions (i.e., Na+, Ca2+, Ag+, Co2+, Cu2+, Al3+, Zn2+, and Mn4+) on mycelia growth and palmarumycins C-12 and C-13 production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12 were investigated. Three metal ions, Ca2+, Cu2+ and Al3+ were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca2+) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu2+) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al3+) to the medium at 2.0 mmol/L on day 6, the maximal yields of palmarumycins C-12 plus C-13 were obtained as 137.57 mg/L, 146.28 mg/L and 156.77 mg/L, which were 3.94-fold, 4.19-fold and 4.49-fold in comparison with that (34.91 mg/L) of the control, respectively. Al3+ favored palmarumycin C-12 production when its concentration was higher than 4 mmol/L. Ca2+ had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca2+, Cu2+ and Al3+ on palmarumycin C-13 production were further studied by employing a statistical method based on the central composite design (CCD) and response surface methodology (RSM). By solving the quadratic regression equation between palmarumycin C-13 and three metal ions, the optimal concentrations of Ca2+, Cu2+ and Al3+ in medium for palmarumycin C-13 production were determined as 7.58, 1.36 and 2.05 mmol/L, respectively. Under the optimum conditions, the predicted maximum palmarumycin C-13 yield reached 208.49 mg/L. By optimizing the combination of Ca2+, Cu2+ and Al3+ in medium, palmarumycin C-13 yield was increased to 203.85 mg/L, which was 6.00-fold in comparison with that (33.98 mg/L) in the original basal medium. The results indicate that appropriate metal ions (i.e., Ca2+, Cu2+ and Al3+) could enhance palmarumycin production. Application of the metal ions should be an effective strategy for palmarumycin production in liquid culture of the endophytic fungus Berkleasmium sp. Dzf12.