Abstract: 5-Deoxygentamicin C.sub.2b and 6'-N-methyl-2-hydroxy- and 6'-N-methyl-5-deoxygentamicins C.sub.2b are prepared, as the major fermentation products, by culturing a nutrient medium containing carbohydrates, a source of assimilable nitrogen, essential salts and either D-streptamine or 2,5-dideoxystreptamine with a mutant of Micromonospora purpurea and isolating the fermentation products from the nutrient medium. The fermentation products are acylated with an ester of an .omega.-[N-(benzyloxycarbonyl)amino]-.alpha.-hydroxy-lower-alkanoic acid after first blocking the primary amino group at the 2'-position with an amine-protecting group, followed by catalytic hydrogenolysis of the benzyloxycarbonyl group and removal of the amine-protecting group to prepare the 1-(.omega.-amino-.alpha.-hydroxy-lower-alkanoyl) derivatives.

Abstract: The invention provides a process for the preparation of antibiotic-producer Micromonospora strains having modified genetic material, wherein a protoplast suspension is prepared with lysozyme, under osmotically buffered conditions ensured by sucose, from each culture of the two genetically marked mutants of the antibiotic-producer Micromonospora strain following cultivation in a glycine medium, both suspensions obtained are combined in the presence of polyethylene glycol, and incubated at room temperature, the resulting fused protoplasts are suspended in soft agar, then plated on an agar plate containing sucrose, prolin and inorganic salts, incubated for 20 to 30 days, and finally all mutants are selected from the regenerated colonies which are sure to have genetic material different from that of the parent strains.The process can be advantageously applied to improve productivity of antibiotic-producer strains having industrial importance.

Abstract: 2-Hydroxygentamicins B, B.sub.1 and A.sub.3 and 2-hydroxy antibiotics JI-20A and JI-20B are prepared as fermentation products by culturing a nutrient medium containing carbohydrates, a source of assimilable nitrogen, essential salts and D-streptamine with a mutant of Micromonospora purpurea, and isolating the said fermentation products from the nutrient medium; the fermentation products are acylated with an ester of an .omega.-(N-benzyloxycarbonyl)amino-.alpha.-hydroxy-lower-alkanoic acid, after first blocking the 6'- and/or 2'-amine group with an amine-protecting group, followed by catalytic hydrogenolysis of the benzyloxycarbonyl group and removal of the amine-protecting groups to prepare the 1-N-(.omega.-amino-.alpha.-hydroxy-lower-alkanoyl) derivatives.