Abstract
Decolorization of RBBR, Poly R-478, Poly S-119, and Azure B by 30 wood-rotting fungi was evaluated for screening of wood-rotting fungi for bleaching of unbleached kraft pulp. Decolorization of RBBR was observed for 20 strains, in which 15 strains also showed decolorization of Poly R-478. Among the 15 strains that showed Poly R-478 decolorization, 6 strains decolorized Poly S-119, and in the 6 strains, 3 strains decolorized Azure B.
Decolorization of each dye in vitro by laccase (Lac), manganese peroxidase (MnP), and lignin peroxidase (LiP) were studied. RBBR was decolorized extensively by all of the enzymes. Poly R-478 was decolorized by MnP and LiP, but was not decolorized by Lac. Poly S-119 and Azure B were decolorized effectively by LiP; however, MnP and Lac were not efficient for decolorization of Poly S-119 and Azure B. The results suggested that decolorization of RBBR detected strains that produced only laccase, or strains that showed low ligninolytic activity, and decolorization of Poly S-119 or Azure B was suitable for detection of strains that produce lignin peroxidase. Compared with these 3 dyes, decolorization of Poly R-478 was more appropriate for selection of strains that produce MnP. These results showed that Poly R-478 was most suitable dye for screening of biobleaching fungi of unbleached kraft pulp because MnP was reported to be effective enzyme for bleaching of unbleached kraft pulp.
