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(+), Ca(2+), Ag(+), Co(2+), Cu(2+), Al(3+), Zn(2+), and Mn(4+)) 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, Ca(2+), Cu(2+) and Al(3+) were exhibited as the most effective to enhance mycelia growth and palmarumycin production. When calcium ion (Ca(2+)) was applied to the medium at 10.0 mmol/L on day 3, copper ion (Cu(2+)) to the medium at 1.0 mmol/L on day 3, aluminum ion (Al(3+)) 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. Al(3+) favored palmarumycin C(12) production when its concentration was higher than 4 mmol/L. Ca(2+) had an improving effect on mycelia growth of Berkleasmium sp. Dzf12. The combination effects of Ca(2+), Cu(2+) and Al(3+) 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 Ca(2+), Cu(2+) and Al(3+) 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 Ca(2+), Cu(2+) and Al(3+) 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., Ca(2+), Cu(2+) and Al(3+)) 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.