Effects of Calcium on Growth, Mineral Elements and Cadmium Content of Exophiala pisciphila under Cadmium Stress

Purpose To study the effects of different calcium (Ca²⁺) concentrations on the growth, mineral nutrition and cadmium (Cd) content of a dark septate endophytic fungus, Exophiala pisciphila, under Cd stress.

Methods Five Ca²⁺ concentration levels (0.045, 0.225, 0.450, 2.250 and 4.500 mmol/L) were set as treatments in the experiment to determine the mycelial dry weight, spore number, pH value of culture solution and the contents of Cd, Ca, nitrogen (N), magnesium (Mg), sulfur (S) and phosphorus (P) of E. pisciphila under 100 mg/L Cd stress. And the correlations among the above-mentioned indexes were analyzed.

Results Under Cd stress, 0.225 mmol/L Ca²⁺ treatment resulted in the highest mycelial dry weight and spore number of E. pisciphila; the Cd content in the mycelium was the highest under 0.450 mmol/L Ca²⁺ treatment. Different concentrations of Ca²⁺ could significantly affect the content of Mg, N, P, Ca, and S elements in the mycelium of E. pisciphila; correlation analysis showed that there were significant differences in the effects of different mineral elements on the accumulation of dry weight, Cd and Ca in mycelium; there was a synergistic effect between Cd content in mycelium and the absorption of Mg and P under Cd stress; adding exogenous Ca to the culture medium could improve the mycelium’s absorption of Ca and S elements in the nutrient solution.

Conclusion During the cultivation process of E. pisciphila, adding an appropriate amount of Ca²⁺ can promote mycelial growth. The addition of 0.225 mmol/L Ca²⁺ is most conducive to the growth of mycelium and steamed buns, and also conducive to the accumulation of N, P, Mg, and S. In order to reduce the adsorption of Cd by mycelium, an appropriate amount of P and Mg can be added. Inappropriate concentrations of mineral elements can actually poison mycelium growth.