De novo production of mandelic- and 3-phenyllactic acid from lignocellulosic feedstock through Phlebia radiata IBWF-87241

Background Phlebia radiata is a white-rot basidiomycete that secretes a repertoire of oxidative enzymes making it a promising organism for the sustainable bio-production of aromatic compounds during lignocellulose-containing cultivation. Here, we investigate the association between wood supplementation and extracellular production of aromatic α-hydroxy acids by P. radiata IBWF 87241 under defined axenic conditions, while accompanying changes in extracellular oxidative enzyme activity and residual wood fibres were characterized using enzyme assays and ATR-FTIR spectroscopy. Results GC–EI–MS analysis of culture filtrate extracts, confirmed by authentic standards, revealed two aromatic α-hydroxy acids produced exclusively under wood-containing conditions. Mandelic acid and 3-phenyllactic acid were produced by P. radiata in ½ soy medium supplemented with 1% (w/v) spruce wood powder, but were absent from un-supplemented and uninoculated controls across repeated cultivation experiments. Continuous monitoring of the cultivation shows that extracellular laccase activity increased throughout fermentation and reached a maximum on day 7, whereas H₂O₂-dependent ABTS oxidation remained low throughout the experiment, while esterase activity showed a minor transient increase. ATR-FTIR analysis of recovered wood powder revealed reproducible treatment-associated spectral differences relative to untreated controls in regions assigned to lignin- and carbohydrate-associated functional groups. Scale-up cultivation in a 20 L stirred-tank bioreactor yielded preliminary titers of 0.79 mg/L mandelic acid and 4.11 mg/L 3-phenyllactic acid, establishing baseline production levels under controlled process conditions. Conclusions These findings establish P. radiata IBWF 87241 as a non-engineered fungal host for the production of aromatic α-hydroxy acids under wood-containing cultivation conditions and provide a quantitative baseline for future metabolic engineering and bioprocess optimisation strategies targeting mandelic acid and 3-phenyllactic acid production. To our knowledge, this is the first report of production of mandelic acid and 3-phenyllactic acid by P. radiata under defined cultivation conditions. The combined characterization of extracellular oxidative activity, FTIR spectral differences in recovered wood, and aromatic α-hydroxy acid production provides a framework for future investigations of extracellular oxidative metabolism, substrate-associated spectral alterations, and aromatic metabolite formation during fungal lignocellulose conversion.