Role of Organic Acids in the Manganese-Independent Biobleaching System of Bjerkandera sp. Strain BOS55

Abstract

Bjerkandera sp. strain BOS55 is a white rot fungus that can bleach EDTA-extracted eucalyptus oxygen-delignified kraft pulp (OKP) without any requirement for manganese. Under manganese-free conditions, additions of simple physiological organic acids (e.g., glycolate, glyoxylate, oxalate, and others) at 1 to 5 mM stimulated brightness gains and pulp delignification two- to threefold compared to results for control cultures not receiving acids. The role of the organic acids in improving the manganese-independent biobleaching was shown not to be due to pH-buffering effects. Instead, the stimulation was attributed to enhanced production of manganese peroxidase (MnP) and lignin peroxidase (LiP) as well as increased physiological concentrations of veratryl alcohol and oxalate. These factors contributed to greatly improved production of superoxide anion radicals, which may have accounted for the more extensive biobleaching. Optimum biobleaching corresponded most to the production of MnP. These results suggest that MnP from Bjerkandera is purposefully produced in the absence of manganese and can possibly function independently of manganese in OKP delignification. LiP probably also contributed to OKP delignification when it was present.

Decolorization of salt-alkaline effluent with industrial reactive dyes by laccase-producing basidiomycetes strains

“…For the in vivo decolorization, 5 ml of the synthetic textile effluent (pH 8Á1) was added to the Erlenmeyer flasks containing the microorganism cultivated in synthetic medium, and the medium decolorization was assessed after 24 h. For the in vitro decolorization, the content of the Erlenmeyer flasks was filtered to obtain free cell extracts. The presence of H 2 O 2 in the enzymatic extract was determined using horseradish peroxidase (Moreira et al 1998). Then, 5 ml of the synthetic textile effluent was added to the extracts, and the decolorization was verified during several time intervals, up to 24 h. The colour reduction was determined spectrophotometrically at 625 nm.…”

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

“…These results suggest that LiP, but not MnP, is involved in the brightening of E-OKP by whiterot fungi under Mn(II)-less culture conditions. Moreira et al, reported that an increase in the physiological concentration of VA and oxalate as well as an enhancement of MnP and LiP production were observed, and that these factors contributed to greatly improved production of superoxide anion radicals, which may have accounted for the more extensive biobleaching observed [11]. However, since Mn(II) is essential for the production of superoxide anion radicals under the MnP reaction system [12,13], it is questionable whether superoxide anion radicals were produced under Mn(II)-free culture conditions.…”

“…These results suggest that LiP plays an important role in the brightening of manganese-less E-OKP by both P. sordida YK-624 and P. chrysosporium under Mn(II)-free culture conditions. Moreira et al, reported that the addition of simple physiological organic acids results in two-to three-fold gains in brightness compared with control cultures without organic acids, and that the stimulation is attributed to enhanced production of MnP and LiP ( [11]). Therefore, the effect of malonate and glyoxylate addition on the brightening of E-OKP by P. sordida YK-624 was examined ( Figs.…”

“…Moreover, the same group proposed that MnP from Bjerkandera sp. BOS55 is intentionally produced in the absence of Mn and can possibly function independently of Mn in OKP delignification [11]. However, as Mn (II) is thought to be essential for production and expression of MnP produced by typical white-rot fungi, it is questionable whether MnP is involved in the delignification of manganese-less OKP.…”

Conifer root and butt rot caused by Heterobasidion annosum (Fr.) Bref. s.l.

“…Oxalate appears to have versatile roles in fungi. It has been proposed to have an important connection with manganese peroxidase (MnP) and manganese in the oxidation of aromatics (Lequart et al ., 1998; Moreira et al ., 1998; Shimada et al ., 1994). Oxalate can also function in lignin peroxidase (LiP) systems (Popp et al ., 1990).…”