Biological Delignification of ¹⁴C-Labeled Lignocelluloses by Basidiomycetes: Degradation and Solubilization of the Lignin and Cellulose Components

ABSTRACT

Three basidiomycetes, NRRL 6464, Pleurotus ostreatus, and Phanerochaete chrysosporium, were evaluated for their ability to both solubilize and metabolize to CO₂ differentially ¹⁴C-labeled, naturally complexed lignocellulosics (LC). The fungi were grown on either ¹⁴C-lignin (L*C) or ¹⁴C-glucan (LC*) substrates for 20 da at 26 C. Several nutrient nitrogen (N) levels were employed to determine if this variable could influence these fungi to preferentially degrade the lignin or glucan component of LC. Pleurotus ostreatus and P. chrysosporium degraded 20% of the L*C component, whereas NRRL 6464 converted 40% of the ¹⁴C-lignin component to ¹⁴CO₂ at 2 mM N or less. At 20 mM N, lignin degradation was suppressed 15 and 60% for P. ostreatus and P. chrysosporium, respectively, after 20 da growth. NRRL 6464 was relatively unaffected by the N levels. With all three fungi, increasing levels of N yielded progressively higher ¹⁴CO₂ evolution from the LC* substrates.

Key Words:

• biological delignification
• Basidiomycetes
• lignin solubilization