Isolation and Investigation of the Effect of Soil and Textile Wastewater Bacteria on Decolorization of Industrial Dyes

Introduction: Azo dyes are the most commonly used colors in textile industry. These colors are among the pollutant materials in the environment. Moreover, they are discharged into the environment in combination with industrial wastewater and pollute the ecosystem. The purpose of this study was to isolate and detect bacteria biodegrading Methyl Red and Rubin Dyprsy colors from dye waste water.   Materials & Methods: The soil samples and wastewaters from textile dyeing workshops, were utilized in this study. The samples were cultivated on a nutrient agar (N.A) medium containing the desired colors, and some of them were isolated from bacterial colonies after checking. After purification, 100 μl of bacterial stocks and colors at a concentration of 200 ppm were inoculated into the medium containing nutrient broth (N.B) with pH=7. Subsequently, the samples were incubated at 30° C for 6-7 days. The samples were separated and optical density of samples was measured using spectrophotometer after centrifugation in appropriate wavelength for each color (450 nm for Rubin Dyprsy and 490 nm for Methyl Red). Moreover, Gram staining and biochemical tests were carried out to identify strains.   Findings: According to the results, 8 Gram-positive cocci and coccobacilli strains showed the most capability to degrade evaluated colors. The highest rates of decolorization by O3 and Y4 were observed for Rubin Dyprsy (46.80%) and Methyl Red (80%), respectively.   Discussion & Conclusions: The results showed that indigenous strains can be used for biodegradation of industrial dyes under applicable conditions.