Scanning electron microscopy investigations on bis(2-ethylhexyl)phthalate treatedMycobacterium cells

Biocatalysis of Steroids by Mycobacterium sp. in Aqueous and Organic Media

Mycobacterium sp. can convert steroids such as β-sitosterol, campesterol, and cholesterol, by selective side-chain cleavage and oxidation of the C3 hydroxyl group to a ketone, into key intermediates that can be easily functionalized to yield commercially interesting pharmaceutical products. In aqueous systems, the biocatalysis is limited by the low solubility of the steroids in water. Several strategies have been introduced to tackle this limitation, e.g., formation of cyclodextrin-steroid complexes and generation of aqueous microdispersions with steroid particle size in the range of hundreds of nanometers. Still, the introduction of an organic phase acting as a substrate and/or product reservoir is a well-established and relatively easy to implement strategy to overcome the sparing water solubility of steroid molecules. However, the organic phase has to be carefully chosen to prevent tampering with the activity/viability of microbial cells.In this chapter, we describe the methodology for the biocatalysis of β-sitosterol to 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD), both in aqueous and organic:aqueous systems. In the latter case, both traditional organic solvents and green solvents are proposed.

Biocatalysis of Steroids with Mycobacterium sp. in Aqueous and Organic Media

Mycobacterium sp. can convert steroids such as β-sitosterol, campesterol, and cholesterol into commercially interesting products. In aqueous systems, the biocatalysis is limited by the low solubility of the steroids in water. This may be overcome by the introduction of an organic phase acting as a substrate and/or product reservoir.In this chapter, we describe the biocatalysis of β-sitosterol to 4-androstene-3,17-dione (AD) and 1,4-androstadiene-3,17-dione (ADD) both in aqueous and organic-aqueous systems. In the latter case, both traditional organic solvents and green solvents are proposed.

Microbial steroid transformations: current state and prospects

Studies of steroid modifications catalyzed by microbial whole cells represent a well-established research area in white biotechnology. Still, advances over the last decade in genetic and metabolic engineering, whole-cell biocatalysis in non-conventional media, and process monitoring raised research in this field to a new level. This review summarizes the data on microbial steroid conversion obtained since 2003. The key reactions of structural steroid functionalization by microorganisms are highlighted including sterol side-chain degradation, hydroxylation at various positions of the steroid core, and redox reactions. We also describe methods for enhancement of bioprocess productivity, selectivity of target reactions, and application of microbial transformations for production of valuable pharmaceutical ingredients and precursors. Challenges and prospects of whole-cell biocatalysis applications in steroid industry are discussed.