Biodegradation of textile dye Reactive Blue 160 by Bacillus firmus (Bacillaceae: Bacillales) and non-target toxicity screening of their degraded products

The study was envisioned to evaluate the decolorization of Reactive Blue 160 (RB160) dye by using indigenous microbes. Contaminated soil from textile dye industry was collected from Noyyal river basin, Tamil Nadu, India. Potential dye degrading bacterial strain was recognized as Bacillus firmus by 16SrRNA gene sequencing analysis. RB160 dye (500 μg/ml) was effectively degraded by B. firmus and toxicological analyses were performed with RB160 and their degraded product. Phytotoxicity revealed that degraded product of RB160 into non-toxic nature by B. firms. Toxicity assays were carried out on root cells of Allium cepa and human skin cell line (CRL 1474). Toxicity analysis of A. cepa and cell line signifies that dye exerts toxic cause on the root cells and IC(50) values of RB160 showed toxic to human skin cell lines, while degradation products of the dye are moderately less in toxic. Zebrafish embryo toxicity also evaluated by RB160 and degraded product on phenotypic deformation, survival, hatching and heartbeat rate. However, RB160 with concentration of 500 μg/ml decrease in the survival, hatching, heartbeat rate and induced phenotypic alterations. In which, degraded products exhibited significant development in zebrafish embryos as compared to dye. Based on the studies effects of RB160 and capability of B. firmus can effectively degrade RB160, and their degraded products were harmless to the environments and aquatic system.