The respirometric measurements were carried out to determine
the long-term toxicity of the ITE on the C. globosum IMA1. Fig. 3
illustrates the evolution of the specific OUR (Fig. 3a), the biomass
growth (Fig. 3b) and the COD (Fig. 3c) of samples taken from a
cultivation of the fungus strain on undiluted, twice diluted and four
times diluted ITEs corresponding to increased initial concentrations
of indigo dye in the ITE. Results showed that C. globosum IMA1
needs about 2 days to adapt to initial culture conditions (Fig. 3a).
The specific OUR increased significantly, from the 2nd day to the
5th day, due to the metabolism activities including mycelia growth
and degradation of dyes. Therefore, it increased as the activity of
biomass increased (Fig. 3b). The higher specific OUR value of 0.82
mgO2/gTSS/minwas observed at the higher fungal activity (5th day
of culture) corresponding to the high rate of decolourization
(Fig. 3c) and COD removal (Fig. 3d). After increasing the dye concentration
in the ITE, OUR in the batch culture was higher. Therefore,
increasing the indigo dye concentration up to 350 mg/L
corresponding to about 700 mg equivalent COD/L has not a toxic
effect on C. globosum. In contrast, it has a positive effect which results
in high oxygen consumption.