New steroid fermentation processes that produce a variety of intermediates from sterols such as cholesterol and phytosterols have recently been developed.
Especially, two fermentation processes for producing intermediates ADD and 4 AD, respectively, have been put into practice for the production of sex hormones and a diuretic drug, spironolactone. New techniques that consist of fermentation processes and the succeeding chemical syntheses are replacing the conventional processes using diosgenin as the starting material.
The microbial processes have been accomplished by the isolation of mutants whose metabolic pathway in cholesterol degradation have been blocked by the enzyme deletions that have resulted in the accumulation of a large amount of required intermediates, on the basis of the establishment of the preceding ADD fermentation techniques using chelating agents as inhibitors. Furthermore, for the production of corticoids which are a majority of steroid hormones, some microorganisms supplying useful steroid intermediates have been isolated and some new production routes are now being available.