Steroid transformation in aqueous two-phase systems: side-chain degradation of cholesterol by Mycobacterium sp.

Abstract

We report on the use of aqueous two-phase systems for the side-chain degradation of cholesterol into androst-4-ene-3,17-dione (AD) and androsta-1,4-diene-3,17-dione (ADD) by Mycobacterium sp. A problem encountered at the start of this investigation, extensive aggregation of the cells, was solved by careful choice of the polymer and detergent composition of the phase system. The systems showing the best properties were composed of polyethylene glycol, dextran and Brij 35 or polyvinylpyrrolidone, dextran and Brij 35 (or Tween 40). The bacterium maintained in the upper polyethylene glycol-rich (or polyvinylpyrrolidone-rich) phase was found to have high activity. The substrated partitioned to the upper phase or the interface (if present as crystals), while the products had partition coefficients around 2.