Reduction of gentian violet to leucogentian violet by Kurthia sp. and assessment of toxicity

A new strain, Kurthia sp., was found to have great potential to transform a triphenylmethane dye, gentian violet, to leucogentian violet under aerobic conditions. Kurthia sp. decolorized 75 ppm gentian violet intracellularly in 1 h and about 225 ppm dye was decolorized in 4 h without a significant d ecrease in the rate of decolorization in repeated addition mode. The biotra nsformed product was identified as leucogentian violet by thin layer chroma tography, H-1 NMR, C-13 NMR and mass spectra. It was identical in all respe cts with the authentic compound. Leucogentian violet was extracted from the cells (the supernatant did not contain any leucogentian violet) and purifi ed by column chromatography over silica gel. Gentian violet, leucogentian v iolet and the biotransformed product were tested for acute toxicity. There was no significant acute toxicity in leucogentian violet or the biotransfor med supernatant. Up to 600 ppm, leucogentian violet did not significantly i nhibit yeast cell growth, whereas gentian violet inhibited cell growth by 5 0% at the 1.15 ppm level.