Decolorization and biodegradation of remazol brilliant blue R by bilirubin oxidase

The dye-decolorizing potential of bilirubin oxidase (BOX) was demonstrated for an anthraquinone dye, remazol brilliant blue R (RBBR). The dye was decolorized 40% within 4 h by the BOX alone, whereas it was more efficient in the presence of 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), showing 91.5% decolorization within 25 min. The effects of operational parameters on decolorization were examined. The results showed that the decolorization efficiency decreased with increasing RBBR concentration, and a marked inhibition effect was exhibited when the dye concentrations were above 100 mg l− 1. The optimum temperature for enzymatic decolorization was 40 °C. BOX showed efficient decolorization of the dye with a wide pH range of 5–8.5. The maximum decolorization activity occurred at pH 8 with ABTS and at pH 5 without ABTS. Analysis of RBBR ultraviolet and visible (UV–VIS) spectra after BOX treatment indicated that the decolorization of RBBR was due to biodegradation. Our results suggested that ABTS can serve as an electron mediator to facilitate the oxidation of RBBR, and the BOX–ABTS mediator-involved dye decolorization mechanism was similar to that of laccase. Operation over a wide range of pH and efficient decolorization suggested that the BOX can be used to decolorize synthetic dyes from effluents, especially for anthraquinonic dyes.