Production and biotransformation of phytosterol microdispersions to produce 4-androstene-3,17-dione

The current state of knowledge regarding phytosterols biotransformation to produce the steroid intermediate 4-androstene-3,17-dione (AD) shows different technologies. However, the initial concentration of phytosterols in batch cultures is limited due to its low solubility in aqueous media, causing serious difficulties for scaling up because of the low mass transfer. In this chapter, we describe a fermentation method of a phytosterol microdispersion with Mycobacterium sp. B3805 in the context of an integral technology for AD production. The microdispersion generation is based on a patent application that claims the production of an aqueous phytosterol microdispersion with an average size particle of 370 nm, and high stability and solubility in water at high phytosterols concentrations (Harting et al., 2012/US0046254). Our results indicate that up to 20 g/L phytosterols can be biotransformed with this technology allowing a good dispersion and stability of reactants in the fermentation broth.