Screening of white rot fungi for biobleaching of Acacia oxygen-delignified kraft pulp

To reduce the levels of chlorine-based chemicals in Acacia kraft pulp, we sought to isolate white rot fungus strains that could be used for biobleaching. For this purpose, we collected 600 fungal sources from Indonesia and subjected them to a three-step screening method. The first step involved culturing the strains on Acacia mangium wood powder, guaiacol and agar (WGA) medium. Of the 600 sources, 258 strains grew on WGA medium and generated a red color. The second step revealed that 31 of the 258 strains could degrade extractive-free A. mangium wood powder. The third step examined the ability of the strains to bleach A. mangium oxygen-delignified kraft pulp (A-OKP) under various pH conditions and showed that five strains could biobleach A-OKP at pH 5, 6, and 8. In contrast, the biobleaching abilities of Trametes versicolor and Phanerochaete chrysosporium, which served as standards, were much lower than those of the five new strains, particularly at pH 8. These five strains may be useful for biobleaching of A-OKP.