Yeasts
 A process for the preparation of a stable diploid of Candida lipolytica which comprises (a) in a first stage, separately cultivating two haploid strains of Candida lipolytica of opposed sign in a medium rich in assimilable carbon nutrient; (b) in a second stage, cultivating the two resultant strains together in a medium poor in assimilable carbon nutrient; and (c) in a third stage, after the appearance of diploid colonies, treating them with a mutagenic agent to stabilize them. The invention also comprises a process for the preparation of .alpha.-ketoglutaric acid which comprises cultivating a diploid strain obtained by crossing two Candida lipolytica haploid strains of opposite sign in a medium containing, as source of assimilable carbon, at least one hydrocarbon. 
Institut Francais du Petrole Institut Francaise du Petrole, des Carburants et Lubrifiants
Y C C
Y10S C12P C12N
additional inventional inventional
Daniel Jean-Pierre Claude Paul
Binet Desmarquest Gaillardin Maldonado