Extracellular Enzymatic Activities of Bacterial Strains Isolated from Tunisian Biotopes: Decolorization and Detoxification of Indigo Carmine

Eleven bacterial strains, isolated from various Tunisian biotopes, were characterized for their lignin degradation activities and were screened for Indigo Carmine (IC) decolorization for the first time. Results revealed that these isolated strains were able to decolorize IC. Based on this property, the newly isolates crude filtrates (NICF) showed that eight ones prove the effectiveness for IC degradation (100 mg). More than 80% of IC could be decolorized within 12 h under non-optimised conditions. The UV–Visible absorption spectra and FT-IR analysis of the degradation products showed an IC decolorization and/or transformation, proving the enzyme’s role in dye decolorization. Furthermore, the phytotoxicity and the cytotoxicity using Vero and erythrocyte cells were performed to evaluate the acute toxicity of the treated and untreated dye. The results showed that some NICF can decrease and sometimes detoxify IC. In fact, NICF decolorize the toxic IC into non-toxic products. These NICF, acting as powerful tools, could be effectively used to decolorize and to bioremediate rich-dye-textile effluents and found worthy of investigation for potential applications in restoration work and other biotechnological uses.