Engineered autolytic yeast strains secreting Kluyveromyces lactis beta-galactosidase for production of heterologous proteins in lactose media.

Secretion of the heterologous Kluyveromyces lactis beta-galactosidase into culture medium by several Saccharomyces cerevisiae osmotic-remedial thermosensitive-autolytic mutants was assayed and proved that new metabolic abilities were conferred since the constructed strains were able to grow in lactose-containing media. Cell growth became independent of a lactose-uptake mechanism. Higher levels of extra-cellular and intra-cellular beta-galactosidase production, lactose consumption and growth were obtained with the LHDP1 strain, showing a thermosensitive-autolytic phenotype as well as being peptidase-defective. The recombinant strain LHDP1 presented the highest beta-galactosidase yields from biomass and the lowest ethanol levels from lactose. This strain is effective for the heterologous production and release of K. lactis beta-galactosidase into the extra-cellular medium after osmotic shock.