Indole yield was measured in nutrient broth liquid medium, supplemented with 10 mM of NH and 10 mM L-tryptophan.
The cultures were incubated in the dark at 28 c, under agitation, for 24 h.
bacterial cells were removed from the culture by centrifuging at 5000 g for 10 min.
The indole present in the supernatant was assayed according to a standard method described by Gordon and Weber in which the hormone present in the culture reacts with Salkowski reagent, quantitatively measured on a spectrophotometer at 530 nm.
Kinetics of indole production was calculeted from a standard curve and expressed as indole equivalents per ml.
Comparative experiments were performed twice, each with four replicates per treatment.