1992 Volume 46 Issue 3 Pages 426-434
Screening of fungi having ability to suppress light-induced color reversion of mechanical pulps (GP, PGW and TMP) was conducted by using 8 wood-rot fungi. Treatment of unbleached pressurized groundwood pulp (PGW) with Stereum hirsutum followed by alkaline hydrogen peroxide bleaching was found to give relatively high effect on depression of the color reversion of PGW. The effect was 23% to that of the untreated pulp. And furthermore, treatment of unbleached PGW with Trametes seriatis followed by bleaching was also found to be effective to depression of the color reversion of PGW. The effect was 16% to that of the untreated pulp. On the contrary, no highly suppressive fungus against the color reversion of GP and TMP was found among 8 fungi tested here. However, T. seriatis and S. hirsutum suppressed 17% and 14%, respectively, to the color reversion of TMP. Futhermore, S. hirsutum could also suppress 16% to that of the color reversion of GP.
The fungi having great suppressive effect on light-induced color reversion can be screened out through the following four steps. Fungi depressing post color (P. C.) number of the pulps in the early stage of incubation were selected (1) after the treatment of mechanical pulps with fungi, (2) after the treatment with extracellular crude enzyme solution and Z (3) after the treatment with crude enzymes prepared from extracellular crude enzyme solutions. And in the final step, investigation to find out best conditions for maximizing suppression of the color reversion should be made by using the selected fungi. The screening method can be applied to the selection of microorganisms having ability to suppress light-induced color reversion of mechanical pulps.
