Efficient secretion of human lysozyme from the yeast, Kluyveromyces lactis

Efficient secretion of human lysozyme from the yeast, Kluyveromyces lactis, was achieved by using more stable vectors in the order of S11 replication origin-containing episomal vector < full-length K. lactis plasmid pKD1-containing vector < centromeric vector < chromosome-integrated vectors. Cells containing a PGK (phosphoglycerate kinase) promoter-driven integration vector grown in non-selective rich medium achieved the highest level of secretion, ∼100 μg lysozyme secretion ml −1 culture: this level was ∼10-fold higher than that achieved by episomal vectors. An additional copy of the protein disulfide isomerase gene further facilitated the secretion.