High-Level Production of the Natural Blue Pigment Indigoidine from Metabolically Engineered Corynebacterium glutamicum for Sustainable Fabric Dyes

The textile industry has caused severe water pollution by using many toxic chemicals for producing fabric dyes. In response to this problem, indigoidine has attracted attention as an alternative natural blue dye, but it is necessary to achieve a high-level production to compete with synthetic blue dyes. Here we report a metabolically engineered Corynebacterium glutamicum capable of producing indigoidine to a high concentration with high productivity. First, the blue-pigment indigoidine synthetase (bpsA) gene from Streptomyces lavendulae was expressed in C. glutamicum, which carries strong fluxes toward l-glutamate, a precursor of indigoidine. Production performance of this base strain, already producing 7.3 ± 0.3 g/L indigoidine from the flask, was further improved by streamlining the intracellular supply of the precursors l-glutamate and l-glutamine, strengthening the phosphotransferase system-independent glucose uptake system, channeling carbon fluxes from glycolysis to the tricarboxylic acid (TCA) cycle, and minimizing byproducts formation. Fed-batch fermentation of the final strain BIRU11 produced 49.30 g/L indigoidine with a productivity of 0.96 g/L/h, the highest titer and productivity to date. Finally, indigoidine from the fed-batch fermentation of the BIRU11 strain was used to dye white cotton fabrics to examine its color and performance. This study demonstrates the potential of producing fabric dyes in a sustainable manner by using a metabolically engineered bacterium.