Glycosidation of narbonolide with mycaminose was attempted by feeding narbonolide during the fermentation of a parent or a mutant strain of Streptomyces platensis, a producer of 16-membered macrolide antibiotics, platenomycins.As a result, two new compounds I and II were isolated from the fermentation broth and identified as 5-0-mycaminosyl narbonolide (I) and 9-dihydro-5-O-mycaminosyl narbonolide (II), respectively. Physicochemical and antimicrobial properties of I and II are also referred to.Hitherto, a number of aglycones of macrolide antibiotics have been isolated,'-') and used for the elucidation of the biosynthetic pathway of this antibiotic group, e.g. erythromycin,') picromycin') and platenomycins.11)As reported previously, the authors isolated narbonolide, the aglycone of narbomycin, from the culture of Streptomyces venezuelae MCRL-0376 which produced narbomycin and picromycin as major antibiotics, '','') and succeeded in the bioconversion of biologically inactive narbonolide into active antibiotics (narbomycin and picromycin) by glycosidation of the aglycone.9)In 1972, rosamicin was reported") to consist of an aglycone identical with that of cirramycin AI and a sugar which was identified as desosamine. Considering that rosamicin is constructed from a 16-membered aglycone and a sugar usually found in 12-or 14-membered macrolide antibiotics, it was conversely assumed that a new antibiotic might be obtained by combining a sugar normally present in 16-membered macrolide antibiotics with a 14-membered macrolide aglycone.Thus, glycosidation of narbonolide with mycaminose (a sugar component of 16-membered macrolide antibiotics, such as platenomycin, leucomycin, spiramycin, cirramycin, tylosin, carbomycin etc.) was attempted by adding narbonolide during the fermentation of platenomycin-producing Streptomyces platensis MCRL-0388141 and its blocked mutant (strain U-21). Two new compounds I and II were successfully derived from narbonolide.In this paper, the isolation and characterization of these biotransformed compounds I and II as 5-0-mycaminosyl narbonolide and 9-dihydro-5-O-mycaminosyl narbonolide respectively is described.
Microorganism and FermentationThe strains employed in this investigation were Streptomyces platensis subsp. malvinus MCRL-0388, a producer of the platenomycins and a mutant strain U-21. Strain U-21 was derived by treatment of the parent strain with ultraviolet irradiation. Strain U-21 was completly blocked in an early stage of platenomycin biosynthesis and unable to synthesize the antibiotics de novo. However, this