Betulin biotransformatiom by Rhodococcus actinobacteria

The ability of Rhodococcus actinobacteria to biotransform betulin, a vegetational pentacyclic lu-pane triterpenoid, to betulone was proved and reported for the first time. Betulone, the product of regioselective oxidation of a 3p-hydroxyl group of betulin, is a useful intermediate in the synthesis of novel biologically active compounds. Of 104 rhodococcal strains tested from the Regional Specialized Collection of Alkanotrophic Microorganisms R. rhodochrous IEGM 66 was selected because it had the highest betulin-transforming ability. The growing cells of R. rhodochrous IEGM 66 were shown to transform 0.5 g/L betulin to betulone with 72.2% conversion rate within 240 h. A substantial reduction in the time of betulin biotransformation was achieved by using resting cells, wherein betulin (0.5 to 3.0 g/L) conversion to betulone was 60-75% within 96 h.