SECRETION OF LIGNINOLYTIC ENZYMES AND MINERALIZATION OF C-14 RING-LABELED SYNTHETIC LIGNIN BY 3 PHLEBIA-TREMELLOSA STRAINS

Production of ligninolytic enzymes by three strains of the white rot f ungus Phlebia tremellosa (syn. Merulius tremellosus) was studied in bi oreactor cultivation under nitrogen-limiting conditions. The Mn(II) co ncentration of the growth medium strongly affected the secretion patte rns of lignin peroxidase and laccase. Two major lignin peroxidase isoe nzymes were expressed in all strains. In addition, laccase and glyoxal oxidase were purified and characterized in one strain of P. tremellos a. In contrast, manganese peroxidase was not found in fast protein liq uid chromatography profiles of extracellular proteins under either low (2.4 mu M) or elevated (24 and 120 mu M) Mn(II) concentrations. Howev er, H2O2- and Mn-dependent phenol red-oxidizing activity was detected in cultures supplemented with higher Mn (II) levels. Mineralization ra tes of C-14-ring-labelled synthetic lignin (i.e., dehydrogenation poly merizate) by all strains under a low basal Mn(II) level were similar t o those obtained for Phanerochaete chrysosporium and Phlebia radiata. A high manganese concentration repressed the evolution of (CO2)-C-14 e ven when a chelating agent, sodium malonate, was included in the mediu m.