Effects of Zn2+ and Cu2+ on growth,lignin degradation and ligninolytic enzymes in Phanerochaete chrysosporium

The influence of Zn²⁺ (6.0 × 10^–3 –18.0 × 10^–3 M) and Cu²⁺ (4 × 10^–4 –1.2 × 10^–4 M) in the basal medium on mycelial growth (dry weight), activities of lignin peroxidase (Lip), manganese peroxidase (Mnp), solubilization, and mineralization (¹⁴CO₂ evolution) of lignin during a period of 3 weeks was studied in Phanerochaete chrysosporium strain MTCC-787. Highest mycelial growth was obtained at 0.6 M Zn²⁺ and 0.4 M Cu²⁺ levels. Enzyme activities were found to increase up to the highest levels of both the trace elements. However, Zn²⁺ had a relatively more stimulatory effect on Lip production and the reverse was true in case of Cu²⁺. ¹⁴C]Lignin solubilization was also promoted by higher levels of both trace elements. Mineralization of ¹⁴C]lignin was optimal at 6.0 M Zn²⁺ and 1.2 M Cu²⁺. The stimulatory effect of Zn²⁺ on Lip production was correlated with higher rates of ¹⁴C]lignin mineralization.