Chapter 3.5 - Microbial Communities Sustain Indigo Reduction Under Anaerobic Alkaline Conditions in the Indigo Fermentation Fluids

Abstract

Indigo-reducing fermentation, which depends on the action of microbial communities, has traditionally been performed to dye textiles blue in Asia and Europe. This fermentation is carried out under alkaline anaerobic conditions and depends on natural fermentation under atmospheric conditions. Therefore, there is uncertainty regarding the initiation of indigo reduction, depending on the preparation procedure, the fermentation scale, and the raw materials. Indigo reduction normally occurs from 2 days to 2 weeks after the initiation of fermentation. Indigo fermentation can be performed using the composted leaves of Polygonum tinctorium L. (sukumo). Indigo reduction can be attributed to the convergence of the pre-existing microbiota in sukumo. Although research in microbiology is largely focused on a single isolate, there are many practical examples where the performance of microorganisms is realized through the actions of their communities. By studying the microbial metabolisms of this simple microbial community in an extreme environment as well as its changes in relation to environmental factors, we can gain knowledge to manipulate the microbiota toward an optimal state. The microbiota responsible for indigo fermentation can be maintained for more than 1year in some cases. Understanding the transitional changes in community structure is important for utilizing a particular microbial system. By investigating of the entire process, we can understand of the underlying mechanism of both rapid and slow fermentation. Additionally, we can understand the flow of the substances related to the microbiota sustaining the system. In this review, we describe the recent findings on the mechanisms responsible for changes in the microbial community in the indigo fermentation process.