Pyrolysis-gas chromatography-mass spectrometry characterization of wheat straw alkaline-cooking effluents after biological treatment with the fungi Phanerochaete chrysosporium and Ganoderma australe

Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was applied in order to monitor the extent of chemical modification of lignin units after seven-day treatment of paper-industry wastewaters using two ligninolytic fungi. Py-GC-MS after the effluent treatment with Ganoderma australe revealed an increase in the lignin compounds, in which oxidation and shortening of the side chain of lignin molecules have occurred. In addition, no significant alkalilignin weight-loss nor reduction of lignin pyrolysis products were detected. On the other hand, these chemical transformations of lignin units were not observed after the effluent treatment with Phanerochaete chrysosporium. However, a remarkable reduction of lignin pyrolysis products and a large alkalilignin weight-loss were observed. The percentages of decolorization attained at day seven of culture were similar for both fungi. These results are possibly due to the different lignin-degrading mechanisms and/or to the earlier expression of the ligninolytic system of P. chrysosporium, under the experimental conditions assayed. Effluent decolorization could not be attributed to adsorption on the mycelia, since no significant quantity of alkalilignin was found attached to the mycelia of either fungi.