In order to overcome the inhibition in riboflavin bio-synthesis and enhance riboflavin production

plasmids pB1 and pB2 were constructed by the homologous recombination vectors of the recipient riboflavin operon.Using the method of double crossover recombination between plasmids and chromosomes

plasmids pB1 and pB2 were linearized and integrated into receptors to get two strains named B.subtilis GJ04 and GJ05

with rfn and ribP1 promoter being replaced by pB9 promoter and Promoter PnprE being inserted between ribB and ribA gene.The homologous recombination events were confirmed by PCR methods.The obtained strains were genetically stable and could produce riboflavin.The results of shake flask shown that: the production of riboflavin from GJ04 and GJ05 were 8.6% and 11.2% higher in 72 hour than that from the GJ02 with a resistance to roseoflavin.