CONTRIBUTION TO LIGNOCELLULOSE DEGRADATION AND DOC FORMATION FROM A SALT-MARSH MACROPHYTE BY THE ASCOMYCETE PHAEOSPHAERIA-SPARTINICOLA

Specifically radiolabeled [C-14-lignin] lignocellulose and uniformly [U-C-14] lignocellulose from the salt marsh grass Spartina alterniflora were incubated with the ascomycete Phaeosphaeria spartinicola. This fungus is the predominant one found on decaying standing dead S. alterniflora leaves in the salt marsh ecosystem. After 45 days of incubation at 20-degrees-C, 3.3% of the lignin moiety was mineralized to (CO2)-C-14 and 2.7% solubilized to (DOC)-C-14. Mineralization of the polysaccharides was seven times faster than that of the lignin. About 22% of the radioactivity was evolved as (CO2)-C-14 but merely 4% was solubilized to (DOC)-C-14 within the incubation time. Experiments monitoring the ergosterol content of the mycelium incubated with date the carbon conversion efficiency of the fungus as well as the influence of the cinnamyl phenols p-coumaric and ferulic acid on lignocellulose degradation. After 21 days of incubation, P. spartinicola showed a growth yield of 0.45 and 0.38 with and without the additional cinnamyl phenols, respectively. Grown on unextracted S. alterniflora, the fungus caused a loss of organic plant material of about 50% with a corresponding growth yield of 0.38 during the incubation period. Investigation of cupric oxide oxidation products of sound and degraded lignocellulose revealed a preferential utilization of the syringyl and cinnamyl phenols compared with vanillyl phenols.