Abstract: The invention relates to a system for the propagation of yeast and adaptation to ethanol in a sustained manner using a bioreactor (1) which is programmed automatically and in which the propagation and adaptation to ethanol, pH and temperature is carried out, for a secondary fermentation in the tirage of Cava, Champagne and sparkling wines in general. The bioreactor (1) includes a motor (6) with stirring blades, and a temperature-control system comprising a sleeve and an electrical resistor, said bioreactor (1) being associated with a mixing tank (2) which houses the liquor. In addition, a programmed pump (4) is provided between the bioreactor (1) and the mixing tank (2), as well as a programmable automaton with a control panel (5) for automating the process.