Removal of monomer delignification products by laccase from Trametes versicolor

► Effect of laccase on lignin derived phenolic monomers in wheat straw hydrolyzates. ► Identification of three reaction groups of phenolic monomers towards laccase (LRG). ► Compounds of LRG-B and -C important in respect to detoxification for fermentation. ► Different results comparing phenolic monomer analytic and total phenol content. ► HS-SPME/GC–MS powerful method analyzing volatile compounds in hydrolyzates. The influence of a laccase from Trametes versicolor on the removal of phenolic monomers in liquid hot water pretreated wheat straw supernatants (LHW-S) was examined. Beside the total phenol content derived by Folin–Ciocalteu (FC-) assay, phenolic monomers were measured via headspace-solid phase micro-extraction (HS-SPME)/GC–MS. A notable decrease of the phenols was achieved using 0.2 and 0.5U/mL laccase whilst higher dosage showed no improvement. Nearly all kind of monomer phenolic compounds identified in the LHW-S were found to be removed after 24h. However, acetophenone and 4-hydroxybenzaldehyde (HBA) were obviously not affected by laccase. Summarizing, three laccase reaction groups (LRG) of phenolic monomers could be classified: immediate removal (LRG-A), degradation after 1day (LRG-B), no effect of laccase (LRG-C). Additionally, HS-SPME/GC was found to be a powerful tool to study the reaction of laccase and phenolic monomers in complex lignocellulose derived solutions.