Decolorization of Reactive Dyes by Bacteria Isolated from Textile Dye-Contaminated Soil

Abstract

Textile dye-contaminated soil samples were collected for the isolation of heterotrophic bacterial population. The isolates were screened primarily for dye decolorization using Luria Bertani broth containing 100 mgL^-1 of selected reactive dyes namely Blue FNR (BF), Novacron Navy (NN), or Novacron Deep Cherry (NDC). Secondary screening of dye-decolorizing bacterial isolates was carried out in Bushnell Haas medium. The decolorization efficiency of the isolates was estimated spectrophotometrically. The selected isolates were identified by the analysis of their cultural, biochemical, and molecular characteristics. Among 38 bacterial isolates from the dye-contaminated soil, two bacterial genera Klebsiella pneumoniae strain OS-3 and Bacillus tropicus strain OS-8 were found to have strong ability in selected dye-decolorization. The optimum pH and temperature for dye decolorization in static conditions by both isolates were found to be 6-8 and 37°C within 72 hours, respectively. Efficient dye decolorization was observed under static condition in compared to shaking culture. Both isolates were able to induce decolorization in the presence of co-substrate. Starch, sucrose and glucose as a carbon source and yeast extract as an organic nitrogen source induced the efficiency of Blue FNR, Novacron Navy and NDC dyes decolorization, respectively by both isolates. On the other hand, it was observed that the percentage of dye degradation decreased in the presence of inorganic nitrogen source in the medium. Both isolates retained efficiency to decolorize selected reactive dyes by 70-80% at 5% salinity. The strong decolorizing ability in natural conditions indicates that both bacteria could be used in dye-polluted wastewater treatment.

Chittagong Univ. J. B. Sci. Vol. 12 (1 & 2): 91-102, 2024