Helena Podgornik

Transformation of Indigo carmine by Phanerochaete chrysosporium ligninolytic enzymes

Abstract The reaction between P. chrysosporium extracellular ligninolytic peroxidases and the dye Indigo carmine was studied. This dye can be successfully decolorized by both manganese (MnP) and lignin (LiP) peroxidases. By using a proper culture medium composition, a growth medium exhibiting high MnP or high LiP activity was obtained. Additionally, some peroxidase isoenzymes were isolated. Although the dye was successfully decolorised by both groups of extracellular peroxidases, the reaction by MnP was faster. Besides a yellow final product, the decolorization of Indigo carmine by MnP resulted in a red product formation that was not observed at the decolorization by LiP. The final concentration of the red product can be influenced by the pH value of the reaction mixture as well as by the initial dye concentration. The maximum formation of the red product was achieved at pH 5 with 60 mg/liter of the Indigo carmine in the reaction mixture. The red product was isolated and partially characterized using UV-VIS and 1 H NMR spectroscopy, and TLC.

Decolorization rate of dyes using lignin peroxidases of Phanerochaete chrysosporium

The basidiomycetous fungus Phanerochaete chrysosporium excretes extracellular lignin peroxidases (LiP) which were used in decolorization experiments with different commercial dyes. Very similar patterns in the kinetic curves of decolorization for dyes of different chemical classes and structures were observed. Decolorization is nonspecific, i.e., not dependent on the chromophoric system, slightly dependent on the auxochromic group, and not dependent on the sign and distribution of the charge. It is useful for decolorizing a large number of dyes of diverse structural classes.

Laccase production by Phanerochaete chrysosporium– an artefact caused by Mn(III)?

Aims: The possibility of laccase production by Phanerochaete chrysosporium was studied.

The effect of agitation and nitrogen concentration on lignin peroxidase (LiP) isoform composition during fermentation of Phanerochaete chrysosporium.

Convective Interaction Media (CIM) monolithic columns were applied for the HPLC monitoring of Phanerochaete chrysosporium lignin peroxidase (LiP) isoforms during cultivation. The influence of the agitation mode (circular, elliptic) and rate (130 and 200 rpm), as well as the initial nitrogen concentration (1.6-6 mM) in the growth medium was investigated. Identical rotation rate but different agitation modes resulted in different LiP activities and isoenzyme compositions. On the other hand, at different agitation types and rates, similar LiP activities were obtained at different isoenzyme compositions. Although LiP H2 and LiP H6/H7 were predominant isoenzymes obtained at various cultivation conditions, relative isoenzyme amounts differ considerably when initial nitrogen concentration was changed between 1.6 and 5 mM.

Polyoxyethylene stimulates lignin peroxidase production inPhanerochœte chrysosporium

In shaken cultures ofPhanerochœte chrysosporium, different Tweens gave rise to similar and high lignin peroxidase (LiP) activities. The polyoxyethylene-sorbitan (POE-S) moieties isolated from Tweens gave rise to somewhat lower LiP activities, whereas fatty acids isolated from Tweens gave rise to much lower LiP activities than parent Tweens. LiP activity appeared 3 d after addition of Tween 80 if this was added within the first 4 d after inoculation. Of the three chemical moieties contained in Tweens,i.e., fatty acids, sorbitan, and polyoxyethylene (POE), only the latter one significantly stimulated the LiP activity of the culture. The stimulatory effect of POE on the LiP activity increased till its molar mass of approx. 1 kDa, then it levelled off. The quantity of POE in the culture decreased with time. Tween 80, its POE-S moiety and POEs seem to enhance LiP production and not only their release.

Improvements in the determination of manganese peroxidase activity

The existing method of determining the activity of manganese peroxidase (MnP), produced by Phanerochaete chrysosporium, was improved. 2,6-Dimethoxyphenol at 80 mM was used as a substrate and, after the decolorization of the reaction mixture, H2O2 was added and the initial reaction rate was used to determine MnP activity.