Quantification of leuco-indigo in indigo-dye-fermenting suspension by normal pulse voltammetry

Quantification of leuco-indigo is most important for Aizome, Japanese indigo-dyeing; however, there has been no convenient quantitative method. This study demonstrated that normal pulse voltammetry under quiescent conditions can be used to detect leuco-indigo. As a result of quantification of leuco-indigo in the depth direction in fermenting suspensions, the steady-state concentrations of leuco-indigo showed sigmoidal profiles in the depth direction. The steady state is caused by competitive reactions of microbial reduction of indigo and autoxidation of leuco-indigo by O-2 dissolved from the air interface of the suspension. In addition, we investigated the effects of stirring the suspension and adding some nutrients to the concentration profile. The weakened activity was partially recovered by the addition of ethanol and remarkably recovered by the addition of hipolypepton or glucose. Knowledge is essential for the proper management of indigo-dye-fermenting suspensions. (C) 2022, The Society for Biotechnology, Japan. All rights reserved.

Automated summary

This study demonstrated the use of normal pulse voltammetry for the detection and quantification of leuco-indigo in Aizome. The steady-state concentrations of leuco-indigo showed sigmoidal profiles in the depth direction, influenced by competitive reactions of microbial reduction and autoxidation. Understanding these factors is crucial for the proper management of indigo-dye-fermenting suspensions.