Harnessing soybean okara for enhanced microbial production of indigoidine

With the increasing demand for sustainable and eco-friendly dyes, microbial production of indigoidine, a natural blue pigment, has gained significant attention. This study explored the use of soybean okara to enhance the production of indigoidine by engineered Escherichia coli strains. The addition of soybean okara hydrolysates (SOH) was found to facilitate microbial indigoidine production by increasing the availability of ATP and coenzyme A (CoA), both of which are crucial for the biosynthesis of indigoidine. Specifically, incorporating SOH led to a 3.4-fold increase in indigoidine production in 250-mL shake flasks and a 2.9-fold increase in a 5-L bioreactor fermentation. A novel extraction method for intracellular indigoidine leveraging the distinct solubility characteristics of oxidized and reduced indigoidine forms was proposed. The techno-economic and environmental feasibility of indigoidine production processes was evaluated using the laboratory scale optimized data, simulated with SimaPro and SuperPro Designer. Additionally, we developed a sodium hydrosulfite-based dyeing system to directly use fermentation broth for dyeing nylon and cotton, bypassing costly indigoidine purification. This research provides a sustainable and economically feasible process for indigoidine production and application, offering a promising alternative to chemical dyes in the textile industry.