Biodecolorization of azo dye Acid Black 24 by Bacillus pseudomycoides: Process optimization using Box Behnken design model and toxicity assessment

Abstract

Bacterial strain Bacillus pseudomycoides, isolated from domestic wastewater was used to decolorize azo dye Acid Black 24. Response Surface Methodology based on Box- Behnken model was used to optimize the conditions for maximum dye decolorization. High regression coefficient values (adjusted R2=0.9317 and predicted R2=0.8343) confirmed that the predicted values are in compliance with the experimental values implying the appropriateness of the employed polynomial regression model. The adequacy of the model was validated by different descriptive statistics viz. lack of fit, adequate precision, F and p values. 96.79% of dye decolorization was achieved at pH7, temperature 37°C and 40mgL−1 dye concentration. The activities of oxido-reductive enzymes like lignin peroxidase, laccase and azoreductase were found to be induced during the dye decolorization process. The biodegradation of the dye was assessed by HPLC, FTIR and UV spectroscopy. Genotoxicity and phytotoxicity studies substantiated the nontoxic nature of the degraded dye.