β-Sitosterol Bioconversion to Androstenedione in Microtiter Plates

Microtiter plates are routinely used as low-cost miniaturized bioreactors due to the large number of experiments that can be conducted simultaneously under similar conditions and replicate all functions of bench-scale reactors at dramatically smaller volumes. These plates, due to the standard footprint, can be integrated with liquid-handling systems and associated equipment expanding considerably their application and use. However, care has to be taken to operate the microtiter plates in optimized mixing and oxygen transfer conditions, preventing medium evaporation in prolonged experiment runs. Here, we describe the production of 4-androstene-3,17-dione (androstenedione; AD), a key pharmaceutical steroid intermediate, by Mycobacterium sp. NRRL B-3805 via the selective cleavage of the side-chain of β-sitosterol using 24-well microtiter plates.