Our previous studies indicated that MgCl2 stress could not only increase the yield of TGase

but also affect the expression of LuxR family protein

which is an important regulator of microbial metabolism. In order to study the effects of LuxR family protein on the biosynthesis of TGase

the luxR gene disruption plasmid was constructed with the vector of pKC1139. The plasmid was transferred into the protoplasts of Streptomyces mobaraensis by PEG mediated transformation. The recombinant plasmid was inserted into the genome of Streptomyces by a single exchange of homologous recombination. The cell growth and TGase activity of luxR gene disruption mutant of S. mobaraensis were compared with the wild stain. The results showed that the luxR gene disruption mutant was successfully constructed

and that the block of the luxR gene leads to a decrease of the biomass

a synthesis delaying and expression decrease of TGase. These results showed that luxR gene might be an important positive factor on TGase production.