Studies of enzymatic oxidation of TMP-fibers and lignin model compounds by a Laccase-Mediator-System using different C-14 and C-13 techniques

In this work, the results of the enzymatic oxidation of TMP-fibers (thermomechanical pulp) and a well-structured lignin model compound, the dehydropolymer (DHP), were investigated by different C-14 and C-13 methods, caused by a Laccase-Mediator-System (LMS). These methods are the nuclear magnetic resonance spectroscopy (C-13-NMR) with DHP (unmarked) and the determination of the (CO2)-C-14 release of C-14-marked DHP and TMP-fibers. The C-13-NMR measurements were chosen to analyze the structural changes of the LMS-treated DHP model compounds and TMP-fibers qualitatively and quantitatively. The data of (CO2)-C-14 release give an explanation of the demethylation of DHP and TMP-fibers. The effect of the LMS is shown by comparing the results in respect of DHP and TMP-fibers, which were only treated with laccase and of an inactivated LMS as the control. Comparing the results of the C-13-NMR method, in particular the use of the Mediator during the enzymatical treatment, showed significant changes in the structure of the DHP. Also, the TMP-fibers were materially influenced by the LMS. The analysis of the (CO2)-C-14 release data of the C-14-marked DHP and TMP-fibers revealed that the rate of (CO2)-C-14 increases in the C-14-2 atom as well as in the (OCH3)-C-14 group within the first hour of Laccase-Mediator incubation. Therefore, the (CO2)-C-14 release from the DHP was higher than from the TMP-fibers.