Bacterial reduction in genotoxicity of Direct Red 28 dye

Chemosphere. 2009 Mar;74(10):1404-6. doi: 10.1016/j.chemosphere.2008.11.043. Epub 2008 Dec 25.


Direct Red 28 (DR28) is a benzidine-based azo dye widely used in several countries. It has also been a subject of intense research for its anti-prion activity. Like other benzidine-based azo dyes, it is also carcinogenic and toxic. However, there are very few studies addressing its detoxification. In the present study, a Bacillus velezensis strain was used for detoxification of DR28. Toxicity was checked by a battery of highly sensitive genotoxicity assays like comet assay, DNA ladder formation, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay and flow cytometric Annexin V binding assay. HL-60 cell line was used as the test system. All the assays showed an initial increase in toxicity upon biodegradation due to release of mutagenic products, like benzidine and 4-aminobiphenyl, from the dye. These intermediates caused significant DNA damage and induced apoptosis in HL-60 cells. Then the culture degraded these mutagenic intermediates, due to which the toxicity was reduced gradually, finally resulting in nearly complete detoxification.

MeSH terms

  • Analysis of Variance
  • Annexin A5
  • Bacillus / metabolism*
  • Biodegradation, Environmental
  • Cell Line, Tumor
  • Comet Assay
  • Congo Red / toxicity*
  • DNA Fragmentation / drug effects*
  • Environmental Pollution / prevention & control*
  • Flow Cytometry
  • Humans
  • In Situ Nick-End Labeling
  • Mutagenicity Tests


  • Annexin A5
  • Congo Red