Abstract：The industrial strain BIB0830 of Streptomyces thermotolerans can produce acetyl-isovaleryl tylosin(AIV) by bioconversion using tylosin as a processor. Recombinant plasmid pBIB425 containing structural gene of acyB1-B2, pBIB304 containing up-mutant promoter of ermE（ermEp* ）and structural gene of ermE, were derived from pIJ8600. The recombinant strain BIB425, BIB304 and BIB308 were obtained by introducing pBIB425, pBIB304 and pBIB308 containing disruption cassette of nsdA gene (stored by lab) respectively into the industrial strain BIB0830 through intergeneric conjugal transfer. After PCR analysis, they were confirmed to be the positive clones. Compared with the start strain BIB0830, in the level of flask, the bioconversion abilities of tylosin to acetyl-isovaleryl tylosin (AIV) of recombiant BIB425 and BIB308 increased 14% and 22%, respectively .The BIB304 was not affected.
