Reduction of Toxic Effects of Textile Dye, Basic Red-18 on Tilapia Fish by Bioremediation with a Novel Bacterium, Mangrovibacter yixingensis Strain AKS2 Isolated from Textile Wastewater

Due to rapid industrialization and market demand of vibrant textile products, the natural textile dyes have been replaced by the synthetic textile dyes. These synthetic dyes are released in environment with textile wastewater resulting in a major environmental pollution, especially in aquatic ecosystem. Hence, aquatic organisms like fish are highly vulnerable to the pollution caused by dyes of textile wastewater. This study was designed to evaluate the deleterious effects of Basic Red-18 (BR-18) dye on behavior, survivability, haematology and histology of Tilapia fish (Tilapia mossambica) and to minimize these deleterious effects of BR-18 dye by bioremediation with the novel bacteria isolated from textile wastewater. The isolated novel bacteria was identified as Mangrovibacter yixingensis strain AKS2 by 16s rRNA sequencing (Accession no. OM189530). The 30% and 70% mortality rates were observed in fish exposed to commercial BR-18 dye at concentrations of 100 and 200 ppm respectively. Interestingly, the mortality rate of fish was decreased significantly to 10% and 20% when fish were exposed to 100 and 200 ppm BR-18 dye respectively after bioremediation with M. yixingensis strain AKS2. Fish exposed to tap water and bioremediated BR-18 dye solution exhibited typical behavioral responses, whereas fish exposed to commercial BR-18 dye solution exhibited anomalous behavior. Fish subjected to commercial BR-18 dye solution displayed decreased RBC, Hb, but increased WBC levels, demonstrating the dye's haemotoxicity. Contrary, no remarkable haematological toxic effect was found when fish were exposed to bioremediated BR-18 dye indicating the non-toxic character of the bioremediated dye metabolites. Similarly, extensive histological abnormalities in the gill, liver, intestinal, stomach, and heart tissues were seen when fish was cultured in commercial BR-18 dye, but the abnormalities were less significant when fish were raised in bioremediated BR-18 dye. Altogether, it can be concluded that BR-18 dye are toxic to fish, but this toxicity can be minimized by bioremediation with M. yixingensis strain AKS2.