Isolation and Characterization of Alkaliphilic and Thermotolerant Bacteria that Reduce Insoluble Indigo to Soluble Leuco-indigo from Indigo Dye Vat

Abstract

Indigo dye has been used in the textile dye industry for long period. Insoluble indigo are reduced to soluble lezico-indigo before dying textiles. A traditional process for solubilization of indigo using microbial reduction metabolism has been considered as environmentally benign method and as alternative to faster chemical reactions. Thus, fermentation liquor aged for 6 years with Polygonum tinctorium (indigo plant) extracts was used to isolate bacteria able to reduce insoluble indigo. Two bacterial isolates, Al and (55, showed indigo-reducing activity, and were identified as Alkalibacterium sp. and Pseudomonas sp. respectively, with 99% sequence similarity by 16S rDNA sequence analyses. Based on the concentrations of leuco-indigo reduced from indigo, Alkalibacteriwn sp. Al and Pseudomonas sp. G5 showed alkaliphilic and thermotolerant charactertistics, optimally functioning at pH 10.0 and 50 degrees C. Isolation of alkaliphilic and thermotolerant bacterial strains, which can reduce insoluble indigo into letuco-indigo, from Korean traditional fermentation liquor could provide a biological tool to enhance efficiency in the traditional indigo dye by an environmentally friendly manner.