Eco-friendly Indigo Reduction by Using Dietzia sp. KDB1 Strain : Some Variables Required to Develop Process Technology

This study was aimed to develop the reduction process of natural indigo (Indigo/era tinctoria) by using bacterial strain (Dietzia sp. KDB1) separated from Korean traditional fermentation bath. In detail, changes in pH, oxidation reduction potential (ORP), and color intensity (K/S) of dyed ramie fabric were evaluated by using some of alkaline mediums, pH adjustments, and concentrations of KDB1 and indigo, respectively. In terms of pH control and reducing power, buffer solution of NaHCO₃/NaOH was the most effective among the mediums used. In the baths with buffer solution, initial pH 10.7 exhibited faster initiation of reduction and higher K/S than other initial pH values. The bath adjusted at pH 10.0 showed higher K/S and more negative ORP, than the baths adjusted at pH 10.5 and 10.7. Better reducing power was obtained at higher indigo and KDB1 concentrations. With the combination of buffer solution, scale-up, repeat dyeing, and higher KDB1 concentration, K/S range of 9.5–16.0 was obtained at days of 4–6. Use of single bacterial strain for indigo reduction attains a simple, reliable and eco-friendly dyeing process which can be applied as an alternative to sodium dithionite reduction.