Inducible gene copy number amplification for the production of heterologous proteins in Kluyveromyces lactis

In the yeast Kluyveromyces lactis heterologous proteins are efficiently produced and secreted. The amount of product formation, which is dependent on gene dosage, can be increased by copy number amplification of expression vectors. Copy number amplification of vectors based on the natural yeast plasmid pKD1 can be obtained by the induction of the expression of the plasmid site-specific recombinase gene under the control of an inducible promoter. Copy number amplification and expression of the heterologous gene might result in strain instability, that can be overcome by separating the plasmid amplification phase from the protein production phase.