LAUSR

The effect of combined quinone reductase (QR) and lignin peroxidase (LiP) on the depolymerization of technical lignins isolated from soda-anthraquinone (SAQ), steam explosion (S-E), and two sulfite processes (NaE and NaPE) was investigated. While LiP is best known for its ability to degrade lignins, it may also cause lignin re-polymerization due to the random coupling of phenoxy radicals and quinoid intermediates. This study evidenced that the addition of the bioreactor produced QR can to some extent limit the lignin re-polymerization by LiP. The synergistic application of QR and LiP lowered the molecular weights (Mw) of SAQ, NaE, S-E, and NaPE lignins by 31%, 34%, 41%, and 52%, respectively. The thermogravimetric analysis also showed that the thermal stability of the four lignins was reduced, whereas gas chromatography-mass spectrometry analysis showed that the degradation products included monomeric phenols. Therefore, the combined QR and LiP system is a promising approach for lignin valorization.