BIOTRANSFORMATION OF ANTIBIOTICS

I. ACYLATION OF CHLORAMPHENICOL BY SPORES OF STREPTOMYCES GRISEUS ISOLATED FROM THE EGYPTIAN SOIL

Abstract

Incubation of spores, washed mycelium or whole cultures of a Streptomyces sp. with chloramphenicol (I) resulted in the loss of in vitro bioactivity of the antibiotic. Gas chromatographic estimation of an appropriate extract revealed that more than 95% of the antibiotic was inactivated under the specified conditions. The spores inactivated chloramphenicol in an inorganic buffer solution, or in distilled water, without the addition of carbohydrate or external co-factor. However, addition of certain carbon sources to the spores showed a pronounced effect on the chloramphenicol
transformation process and on the relative concentration of the inactivated products. Time-course studies on the spore-catalyzed chloramphenicol transformation activity showed a maximum activity at 12-hour incubation. Addition of glucose or acetate at this point maintained maximum activity. The transformation products were identified as: chloramphenicol-1-acetate (IIa); chloramphenicol-3-acetate (IIb); chloramphenicol-3-propionate (III); chloramphenicol-3-isobutyrate (IV); chloramphenicol-3-butyrate (V); and chloramphenicol-3-isovalerate (VI), by techniques of TLC, CPC, GC, UV, IR, MS and NMR. The microbial characteristics of the isolated
strain include the formation of flexuous gray aerial mycelium with smooth to rough spores, irregular in size. It is an H₂S and melanin former, non-chromogenic, and was inhibited by a streptomycin-producing strain of Streptomyces griseus. The organism was identified as a strain of subspecies of Streptomyces griseus (KRAINSKY 1914) WAKSMAN and HENRICI (1948).