Abstract: The invention concerns a simple and effective process for preparing ?-carotene or lycopene by submerged fermentation with mixed cultures of (+) and (?) strains of the fungus Blakeslee trispora, characterized by high productivity of the B. trispora strains. The high productivity is achieved by virtue of the inventive regime, which acknowledges both the morphological state of the hemi-strains with their filamentous growth state when the strains are mixed (referred to as mating).