Optimization of recombinant fungal laccase production with strains of the yeast Kluyveromyces lactis from the pyruvate decarboxylase promoter

Laccases are multicopper oxidases of wide specificity that catalyze the oxidation of phenolic and related compounds using molecular oxygen as the electron acceptor. Here, we report the production of the Lcc1 laccase of the fungus Trametes trogii in strains of the yeast Kluyveromyces lactis, using the pyruvate decarboxylase promoter (KlPDC1) as an expression system. We assayed laccase production in various strains, with replicative and integrative transformants and with different cultivation parameters. A comparison with Lcc1 enzymes from other yeasts and from the original organism was also performed. The best production conditions were obtained with integrative transformants of an individual strain, whereas cultivation conditions were less stringent than the use of the regulated KlPDC1 promoter could anticipate. The secreted recombinant laccase showed better enzyme properties than the native enzyme or recombinant enzyme from other yeasts. We conclude that selected K. lactis strains, with opportune physiological properties and transcription regulation of the heterologous gene, could be optimal hosts for laccase isoenzyme production.