A Kluyveromyces lactis yeast strain comprising the sequence identified by SEQ ID NO: 1, and methods for the production of sugars (glucose and galactose), ethanol, β-galactosidase and biomass is provided, in which the Kluyveromyces lactis yeast strain is cultured in the presence of a lactose-containing medium. The lactose-containing medium may be milk, whey, whey resulting from the preparation of butter, whey resulting after casein precipitation, milk permeate, whey permeate, acid whey and YPL culture medium.