The ligninolytic activities of Lentinus edodes and Phanerochaete chrysosporium

Abstract

Two important lignin-degrading fungi with existing or potential applications in the production of food, feed and/or fiber products from wood are Lentinus edodes (Berk.; Sing.=Lentinula edodes [Pegler]) and Phanerochaete chrysosporium (Burds). This study discusses their relative ability to degrade lignin and the factors controlling their ligninolytic activity (synthetic 14C-lignin→14CO2). Ligninolytic activity in P. chrysosporium is known to develop after the fungus ceases vegetative growth, and to require both O2 and an exogenous carbon source such as glucose. It has an extracellular ligninase in high titer which is assayed by the oxidation of veratryl alcohol to veratraldehyde. Here, P. chrysosporium was found to have a high capacity for lignin degradation (it was not easily saturated with lignin). Certain inorganic elements, including Fe2+, Ca2+ and Mo6+, were found to stimulate its ligninolytic activity. Calcium addition was required, with 40 ppm Ca2+ giving the highest activity. As in P. chrysosporium, ligninolytic activity in L. edodes was found to require both O2 and an exogenous carbon source. However, in contrast to P. chrysosporium, L. edodes was only moderately ligninolytic, had a lower capacity for lignin degradation (was more easily saturated with lignin), and showed maximal activity only during the vegetative growth period. Also in contrast to P. chrysosporium, ligninolytic activity in L. edodes was not stimulated by Ca2+. Instead, manganese was required, with 10 ppm Mn2+ giving optimal activity. An extracellular ligninase capable of oxidizing veratryl alcohol to veratraldehyde was not detected in L. edodes.