The invention relates to the cultivation of unicellular red algae (URA) for producing biomass for the production of products of interest, such as dry biomass or compounds or mixtures of compounds of interest extracted from the biomass produced, particularly food pigments or colouring agents. The invention more particularly relates to the industrial production of said biomass, which must satisfy an economic equilibrium of profitability, with both an increase in productivity (quantity of biomass and of compounds of interest in the biomass) and an economically acceptable production cost.