Modification of progesterone and testosterone by a food-borne thermophile Geobacillus kaustophilus

Abstract

The present work was carried out to study structural modification of steroids by Geobacillus kaustophilus, a bacterial thermophile present in milk and the environment. Incubation of progesterone and testosterone with G. kaustophilus at 65°C resulted in oxygenated steroid nuclei. The oxygenation of the steroid molecule was stereo specific. Seven metabolites of progesterone─6β/6α-hydroxytestosterone, 20-hydroxyprogesterone, 6β-/6α-20-dihydroxyprogesterone, 5α-pregnane-3,6,20-trione, and 3β-hydroxy-5α-pregnane-6,20-dione─were identified. Four compounds─namely, 66-/6--hydroxytestosterone and 6β/6α-hydroxyandrostenedione─and androst-4-en-3,17-dione were identified as testosterone metabolites. This shows that G. kaustophilus is capable of modifying steroid nuclei at elevated temperatures. G. kaustophilus is a stable thermophile first isolated from milk. Our results show that endogenous steroids present in milk can be modified by G. kaustophilus, causing detrimental effect on human health.