Abstract: Petroleum sulfonates are manufactured by reacting a hydrocarbon stock with a sulfonating agent and neutralizing the sulfonation product. The hydrocarbon stock is pretreated with hydrogen, in the presence of a NiW or NiMo catalyst, under specified conditions: its sulfur content is decreased by at least 50%, but its aromatic hydrocarbon content is decreased by not more than 35%, so that the aromatic hydrocarbons content remains at least 20% b.w. after completion of the pretreatment.

Abstract: 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.