A genome-scale dynamic flux balance analysis model of Streptomyces tsukubaensis NRRL18488 to predict the targets for increasing FK506 production

FK506 is a 23-membered polyketide macrolide with a good immunosuppressant activity for the treatment of autoimmune"diseases. However, the low fermentation yield is a bottleneck to limit its further industrialization and clinical applications. To address this issue, a genome-scale dynamic flux balance analysis (GS-DFBA) model was developed to seek for the bottlenecks of FK506 biosynthesis. After validating under different cultural conditions, lots of targets were predicted successfully with help of Minimization of Metabolic Adjustment (MOMA). Specifically, many uncover targets that heretofore had remained hidden in the complex interconnectedness of central metabolism had also shown significant effects on FK506 accumulation. To validate the model predictions, four identified targets (gcdh, tktB, msdh and ask gene) were engineered in Streptomyces tsukubaensis NRRL18488. All of the engineered strains showed a higher FK506 production, compared with the parent strain. Finally, the best strain HT-Delta gcdh-tktB/msdh/ask with gcdh-deletion and tktB-, msdh- and ask-overexpression could produce 126.61 +/- 4.66 mg/L FK506, 129.8% higher than that of the wild-type strain (55.1 +/- 3.83 mg/L). Results demonstrated that the GS-DFBA model could provide an effective approach in engineering S. tsukubaensis NRRL18488 for FK506 overproduction. This strategy developed here could also be extended to titer improvement of other products. (C) 2017 Elsevier B.V. All rights reserved.