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

Abstract

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.

Characterization of ligninolytic enzyme production in white-rot wild fungal strains suitable for kraft pulp bleaching

“…To the best of our knowledge, information about the bleaching and kappa number reduction of kraft pulp treated with Phlebiopsis spp. had not been previously reported, and we found that this taxa could be as efficient for kappa number reduction (48.3%, Table 3) as the well-studied white-rot species of the genera Trametes, Phanerochaete, and others (Takano et al 2001;Afrida et al 2009). Even the kappa number reductions obtained with the CMU-84/13 strain of I. lacteus were comparable to previously reported values (Table 3).…”

“…Solid-state fermentation assays for evaluating kraft pulp bleaching are usually conducted in Erlenmeyer flasks involving liquid cultures for inoculum preparation (Katagiri et al 1995;Afrida et al 2009), but this approach becomes complicated when handling large numbers of strains. Simpler solid-state fermentation bleaching assays, based on incubating strains directly on kraft pulp in a Petri dish, allow for daily visual corroboration of the progress of the bleaching process.…”

“…The fungal evaluation protocol we present here uses solid medium and Petri dishes from inoculum generation to bleaching via intermediate dye decolorization/guaiacol oxidation assays. It is thus less expensive and simpler than previously reported protocols (Katagiri et al 1995;Afrida et al 2009), and is appropriate for evaluating a large number of strains. Recent strategies to select fungal strains able to bleach lignocellulose include variations in the composition of media, alternative plant biomass, and miniaturized activity assays, reflecting the b Fig.…”

Comparison of the Ability of Several White-rot Fungi to Biobleach Acacia Oxygen-delignified Kraft Pulp

“…versicolor (NBRC 30340) and P. chrysosporium (NBRC 31249) were provided by the National Institute of Technology and Evaluation (NITE) Biological Resource Center (NBRC, Japan). I. lacteus KB-1.1 and L. tigrinus LP-7 were isolated and identified as described elsewhere [14]. All fungi were maintained at 30°C on agar slants containing 0.2% Acacia mangium wood powder, 0.01% guaiacol, and 1.6% potato dextrose agar (PDA).…”

“…Therefore, two fungi are commonly used as species standards when comparing the potential of new strains to produce lignin-degrading enzymes [12,13]. Previously, the ability of 600 white-rot Indonesian fungal sources to biobleach Acacia oxygen-delignified kraft pulp (A-OKP) was screened, with P. chrysosporium and T. versicolor as standard fungi [14]. The biobleaching in vivo activity of the selected fungal strains Irpex lacteus KB-1.1 and Lentinus tigrinus LP-7 was higher than that of P. chrysosporium and T. versicolor.…”