Engineering validamycin production by tandem deletion of γ-butyrolactone receptor genes in Streptomyces hygroscopicus 5008

Paired homologs of gamma-butyrolactone (GBL) biosynthesis gene afsA and GBL receptor gene arpA are located at different positions in genome of Streptomyces hygroscopicus 5008. Inactivation of afsA homologs dramatically decreased biosynthesis of validamycin, an important anti-fungal antibiotic and a critical substrate for antidiabetic drug synthesis, and the deletion of arpA homologs increased validamycin production by 26% (Delta shbR1) and 20% (Delta shbR3). By double deletion, the Delta shbR1/R3 mutant showed higher transcriptional levels of adpA-H (the S. hygroscopicus ortholog of the global regulatory gene adpA) and validamycin biosynthetic genes, and validamycin production increased by 55%. Furthermore, by engineering a high-producing industrial strain via tandem deletion of GBL receptor genes, validamycin production and productivity were enhanced from 19 to 24 g/L (by 26%) and from 6.7 to 9.7 g L-1 d(-1) (by 45%), respectively, which was the highest ever reported. The strategy demonstrated here may be useful to engineering other Streptomyces spp, with multiple pairs of afsA-arpA homologs. (C) 2014 International Metabolic Engineering Society Published by Elsevier Inc. On behalf of International Metabolic Engineering Society.