Fig. 10

Proposed process flowsheets, that are relevant for the production of commercial indigo dye products. Flowsheet A–C. represent flowsheets toward indigo derived via a biological platform, while for Flowsheet D. a chemical platform is assumed. Flowsheet A The flowsheet that is predicted for the considering platform. It has been assumed that indigo is in the medium after the fermentation, and no cell disruption has to take place. The process relies on the precipitation of indigo after the upstream chemical reaction. Depending on the chosen final step, this bioprocess could produce 2 different formulations of the product; either a powder indigo, or a pre-reduced dye solution. The normal writing represents the name of the considered step, while the cursive—the aim of the single flowsheet step or information about discarded or saved feed content. Flowsheet B The flowsheet is for the preparation of indigo by solubilization after the upstream chemical reaction. The process output is a pre-reduced solution only. It has been assumed that the indigo diffuses into the medium after production by cells. Flowsheet C This scenario represents in situ dyeing—the indigo is secreted onto the fabric. The final product is the dyed fabric. Flowsheet D is a comparative diagram of current steps for the production of synthetic indigo by a conventional chemical manufacturing platform, that has been sourced from Paul et al. (2021)