Peroxidase and Aryl Metabolite Production by the White Rot Fungus Bjerkandera sp. Strain BOS55 during Solid State Fermentation of Lignocellulosic Substrates

Ligninolytic enzymes and secondary metabolite production by Bjerkandera sp. strain BOS 55 were monitored during solid state fermentation (SSF) on two lignocellulosic substrates, beech wood and hemp stem wood (HSW). After 6 weeks of SSF, the fungus was responsible for removing 27 and 39% of the Klason lignin as well as 43 and 70% of the apolar extractives on beech and HSW, respectively. The lignin degradation during beech wood decay was very selective. On both substrates, high activities of lignin peroxidase (LiP) and manganese peroxidase (MnP) were detected. The peak activity of LiP was 660nmol ml^-1 min.^-1 on HSW and that of MnP was 1320nmol ml^-1 min.^-1 on beech wood. The presence of several LiP and MnP isoenzymes at different times during the SSF was demonstrated by FPLC profiles of these heme proteins. The production of the secondary aryl metabolites, veratryl alcohol and 3-chloro-p-anisaldehyde, reached peak concentrations of 820 and 90μM, respectively. The enhanced production of these secondary metabolites compared to defined liquid cultures is suggested to be due to the release of lignin degradation products serving as alternative precursors for their biosynthesis. The high production of veratryl alcohol, which is a cofactor known to protect LiP from inactivation by physiological levels of H₂O₂, may account for the high production of active LiP on the lignocellulosic substrates.