Microbial transformation of neomycin by a mutant of neomycin-producing Streptomyces fradiae

Utilizing a mutant of neomycin-producing Streptomyces fradiae mutagenized with neutron radiation, biotransformation of neomycin into modified compounds was studied. The biotransformation products were isolated by ion exchange chromatography and monitored by thin layer chromatography bioautography (TLCB). Antibacterial activity of biotransformation products against ten species of bacteria including four plant pathogens was tested qualitatively by TLCB and detected quantitatively by Oxford cup method. The minimal inhibitory concentration (MIC) of biotransformation products was tested by agar diffusion method. Three isolated transformation products had obvious antibacterial activity against Staphylococcus aureus , Bacillus subtilis , Proteus vulgaris and Pseudomonas solanacarum . At the concentration of 50 μg/ml, the transformation product X had a similar antibacterial effect with neomycin but the transformation product Y and Z showed a decreased effect compared to neomycin except for P. vulgaris and P. solanacarum . However, the results from MIC analysis demonstrated that only the transformation product X maintained the same inhibitory effect with neomycin. Key words : Neomycin, biotransformation, Streptomyces fradiae , mutant, neutron radiation.