Abstract: The present invention discloses intersexual heterozygous Phycomyces strains. These strains show an improved .beta.-carotene productivity and an increased stability when compared with both the wild type and heterokaryotic Phycomyces strains. The present invention also discloses a method for obtaining Phycomyces transformants without using selection markers. Furthermore, a process is provided for manufacturing .beta.-carotene comprising the use of intersexual heterozygous Phycomyces strains in a submerged culture.

Abstract: This invention refers to the obtention of strains of the fungus Phycomyces blakesleeanus accumulated by the .beta.-carotene pigments in amounts which permit the use of these strains in the production on an industrial scale of said pigment. By genetic manipulations, strains simultaneously and constitutively incorporating various stimulating effects have been isolated. The resulting strains produce .beta.-carotene in a proportion of approximately 2.5% of its dry weight, which constitutes almost 1000 times more than that which the natural microorganism would produce under the same conditions. This production level, together with the simplicity in cultivating and manipulating same, makes them interesting in the development of an industrial process for producing .beta.-carotene by fermentation. The .beta.-carotene produced by fermentation, besides its low cost, would have the advantage of not being contaminated with the reagents and catalysts used in the organic synthesis.