Copper increases laccase gene transcription and extracellular laccase activity in Pleurotus eryngii KS004

Abstract

The white-rot fungus Pleurotus eryngii secretes various laccases involved in the degradation of a wide range of chemical compounds. Since the laccase production is relatively low in fungi, many efforts have been focused on finding ways to increase it, so in this study, we investigated the effect of copper on the transcription of the pel3 laccase gene and extracellular laccase activity. The results indicate that adding 0.5 to 2 mM copper to liquid cultures of P. eryngii KS004 increased both pel3 gene transcription and extracellular laccase activity in a concentration-dependent manner. The most significant increase in enzyme activity occurred at 1 mM Cu²⁺, where the peak activity was 4.6 times higher than in control flasks. Copper also induced the transcription of the laccase gene pel3. The addition of 1.5 and 2 mM Cu²⁺ to fungal culture media elevated pel3 transcript levels to more than 13-fold, although the rate of induction slowed down at Cu²⁺ concentrations higher than 1.5 mM. Our findings suggest that copper acts as an inducer in the regulation of laccase gene expression in P. eryngii KS004. Despite its inhibitory effect on fungal growth, supplementing cultures with copper can lead to an increased extracellular laccase production in P. eryngii.

Keywords: Pleurotus eryngii; Induction; Laccase; Transcriptional regulation; White-rot fungi.

Fig. 1

Influence of various Cu concentrations on extracellular laccase activity (enzyme activity units per liter of culture). Vertical bars represent the standard deviation of three independent replicates

Fig. 2

Impact of copper sulfate on mycelial growth of P. eryngii KS004. a Changes in dry weight of mycelia cultured on PDB medium. Vertical bars represent the standard deviation of three independent replicates. b Mycelial growth of P. eryngii KS004 on PDA culture medium with different concentrations of Cu²⁺

Fig. 3

Relative induction effect of copper on pel3 laccase gene transcription