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.

Keywords::

• Geobacillus kaustophilus
• milk
• nuclear magnetic resonance
• progesterone
• testosterone

Acknowledgement

The present work was funded by the College of Graduate Studies, Kuwait University for which ST is thankful. The authors are grateful to SAF at the Faculty of Science, Kuwait University (Project Numbers GS01/01 and GS03/01) for measuring the Fourier transform infrared, mass spectrometry and NMR data during this study.