Figure 5

Introduction of the heterologous flavin facilitator RibM from Streptomyces davawensis enhanced riboflavin synthesis in the high-performance riboflavin production strain BSHP. Two BSHP strains containing pHT01ribM_opt (designated as ribM1 and ribM2) and one strain containing pHT01 (control) were grown in shake flasks in the medium used for industrial riboflavin production. For each strain three shake flask experiments were carried out (n = 3). Different amounts of IPTG were used to induce synthesis of RibM. At the end of fermentation (30 h) residual sugar and the optical density at μ = 600 nm were measured. In all shake flasks the carbon source was completely metabolized and the strains had grown to a very similar cell density. For the cultures induced with 100 μM and 1 mM IPTG the t test gave the result that the RibM containing strains produced more riboflavin (mg/L), which was significant at the 5% level.