Manganese Is Not Required for Biobleaching of Oxygen-Delignified Kraft Pulp by the White Rot Fungus Bjerkandera sp. Strain BOS55

Abstract

The white rot fungus Bjerkandera sp. strain BOS55 extensively delignified and bleached oxygen-delignified eucalyptus kraft pulp handsheets. Biologically mediated brightness gains of up to 14 ISO (International Standards Organization units) were obtained, providing high final brightness values of up to 80% ISO. In nitrogen-limited cultures (2.2 mM N), manganese (Mn) greatly improved manganese-dependent peroxidase (MnP) production. However, the biobleaching was not affected by the Mn nutrient regimen, ranging from 1,000 M added Mn to below the detection limit of 0.26 M Mn in EDTA-extracted pulp medium. The lowest Mn concentration tested was at least several orders of magnitude lower than the K m known for MnP. Consequently, it was concluded that Mn is not required for biobleaching in Bjerkandera sp. strain BOS55. Nonetheless, fast protein liquid chromatography profiles indicated that MnP was the predominant oxidative enzyme produced even under culture conditions in the near absence of manganese. High nitrogen (22 mM N) and exogenous veratryl alcohol (2 mM) repressed biobleaching in Mn-deficient but not in Mn-sufficient culture medium. No correlation was observed between the titers of extracellular peroxidases and the biobleaching. However, the decolorization rate of the polyaromatic dye Poly R-478 was moderately correlated to the biobleaching under a wide range of Mn and N nutrient regimens.

Transformation of Industrial Dyes by Manganese Peroxidases from Bjerkandera adusta and Pleurotus eryngii in a Manganese-Independent Reaction

“…Moreover, paper pulp bleaching by Bjerkandera sp. has been described, suggesting that there is an Mn-independent activity (18). In the present study, dye decolorization in the absence of Mn 2ϩ was also obtained with P. eryngii MnP isoenzymes but not with P. chrysosporium MnP1, suggesting that the Pleurotus and B. adusta enzymes may form a subclass of MnP isoenzymes that oxidize both Mn 2ϩ and a variety of aromatic compounds.…”

Optimization of manganese peroxidase production by the white rot fungus Bjerkandera sp. strain BOS55

“…strain BOS55 showed that MnP isoenzymes were produced in the absence of Mn and that these were distinguished from the LiP isoenzymes. The LiP isoenzymes were incapable of Mn(I1) oxidation [24,28].…”

Lignin peroxidase is involved in the biobleaching of manganese-less oxygen-delignified hardwood kraft pulp by white-rot fungi in the solid-fermentation system

“…Using a modified method of Moreira et al [10], 50 g of OKP (ISO brightness 52%, kappa number 8.5, Mn concentration 20.1 mg/kg pulp) was immersed in 2 l of 5 mM EDTA at room temperature for 12 h to remove Mn ions. The pulp was washed with water, and dried at room temperature to give manganese-less OKP (E-OKP; Mn concentration <0.1 mg/kg pulp).…”

“…Unbleached hardwood kraft pulp (HWKP) contains Mn at a concentration of about 50 mg/kg pulp [6,9], and P. sordida YK-624 utilizes Mn during the biobleaching of HWKP because this fungus can produce MnP and brighten HWKP in a culture containing only HWKP and water [5,6]. However, Moreira et al [10] found that the white-rot fungus Bjerkandera sp. BOS55 extensively delignified and bleached oxygen-delignified hardwood kraft pulp (OKP) without the requirement of Mn.…”