the present invention relates to a new microbial process for the preparation of the compound formula from a compound of general formula wherein r stands for an alkali metal or ammonium ion , by the submerged cultivation of a mold strain able to 6β - hydroxylate a compound of the formula in aerobic fermentation and by the separation and purification of the product of formula formed in the course of the bioconversion . the process comprises cultivating a strain of mortierella maculata filamentous mold species that is able to 6β - hydroxylate a compound of the general formula , on a nutrient medium containing assimilable carbon and nitrogen sources and mineral salts and separating the product formed from the fermentation broth , then isolating the compound of formula and purifying the same . novel strains of mortierella maculata are also disclosed .