Abstract: The spores of Streptomyces sp.WZFF.W-12 isolated from soil in our laboratory to produce microbial transglutaminase(MTG) about 0.24U/ml,were precultured and then treated several times by NTG singly and with hydroxylammonium chloridefor complex genetic mutation. The results showed that some mutants were greatly different from the original strain in morphol-ogy of colony, and that these mutation phenomena were related to the MTG productivity and thereafter used for strainselection. first. Then, test of flocculation-precipitation of proteins through MTG cross-linking as the primary screening andexamination test of MTG production as the secondary screening were successively used to select potent strains. An effectivestrain named Streptomyces sp. WZFF.W-12.var HZ-3 was finally obtained from many regenerative mutants. The MTG activityof this new mutant reached 2.18U/ml,which has been increased about 8 times higher than that of the initial strain. Its geneticquality was proved to be stable by experiments, and its physiological and biochemical characteristics were obviously differentfrom the present strains reported producing MTG.

Key words: Steptomyces, transglutanminase, complex mutation, NTG, hydroxylammonium