Novel indigo-reducing bacterial species

Indigo has been used for thousands of years as a dye, which is traditionally derived from various blue dye plants, including woad (Isatis tinctoria), knotweed (Polygonum tinctorium), Indigofera (Indigofera tinctoria and Indigofera suffruticosa), et. al. As a vat dye, insoluble indigo needs to be reduced to its water-soluble form, leuco-indigo. In the traditional process, indigo reduction occurs by natural fermentation. The indigo-reducing Clostridium isatidis has been isolated from a couched woad (Isatis tinctoria) vat prepared by a traditional medieval European procedure. There are much more indigo-reducing species have been isolated from various Japanese indigo fermentation materials. It is considered that there are more unknown indigo-reducing bacteria in traditional natural indigo.