Stabilization of steroid 11-hydroxylation activity ofCunninghamella elegans protoplasts in organic osmotic stabilizers

Advances in microbial steroid biotransformation

Microbial biotransformations of various steroids are reviewed. Developmental studies on hydroxylation, carbon-carbon bond cleavage, enzymatic catalysis in nonaqueous solvents, use of cyclodextrin medium, cell immobilization, and new microbial reactions are highlighted. Various steroid substrates, their metabolites and the microorganisms used for the transformations are compiled covering the literature for the period 1992-1995.

Effect of inhibitors of cell envelope synthesis on beta-sitosterol side chain degradation by Mycobacterium sp. NRRL MB 3683

The role of the lipid bilayer and the peptidoglycan of the mycobacterial cell wall in the permeation of beta-sitosterol into the cell and its transformation to androst-1-ene-3,17-dione (AD) and androsta-1,4-diene-3,17-dione (ADD) was studied. Specific inhibitors were used at concentrations affecting the biosynthesis of the assumed target structures, but causing only partial cell growth inhibition or exerting no effect on growth. m-Fluorophenylalanine and DL-norleucine which are known to disorganize the biosynthesis of amphipatic components of the outer layer of the lipid bilayer, used at concentrations 250 micrograms/ml and 400 micrograms/ml, respectively, increased the formation rate of AD+ADD from 0.3 (control) to 0.7 and 0.8 mg products/g dry weight/h. The disorganization of the underlying mycolyl-arabinogalactan structure by the action of the ethambutol at the concentration 40 micrograms/ml, at which the cell growth was apparently not affected, caused the decrease of the product formation from 135 mg/l to 70 mg/l. In the presence of isoniazid (350 micrograms/ml) only trace amounts of AD accumulated during 48 hours of transformation indicating much lower activity than that of the intact cells. The most effective among the tested inhibitors of peptidoglycan synthesis were glycine (15 mg/ml) and vancomycin (150 micrograms/ml) which enhanced the transformation activity of the treated cells nearly three times. Increased transformation rate was also obtained by the action of colistin at concentrations ranging from 10 micrograms/ml to 15 micrograms/ml.