Effects of 4 metal ions, Mn²⁺, Cu²⁺, Zn²⁺ and Se²⁺, were determined on level of manganese peroxidase (MnP) expression and degradation efficiency of Strain Xhhh, an inter-kingdom protoplast fusant (IKPF) was constructed for degrading organic pollutants in wastewater from a pharmaceutical plant. Results showed that in terms of specific activity (MnP-SA) level, the four metals were in the order of Mn²⁺ > Se²⁺ > Zn²⁺ > Cu²⁺. A significantly positive correlation (P<0.01) was observed between the MnP-SA level and the specific degradation rate (SDR). The findings provided some important molecular biological parameters that were useful in designing wastewater treatment technology using the IKPF-Xhhh strain. The prospect of application of Strain Xhhh to soil bioremediation was also discussed.