Rapid Degradation of Isolated Lignins by Phanerochaete chrysosporium

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Abstract
Phanerochaete chrysosporium degraded purified Kraft lignin, alkali-extracted and dioxane-extracted straw lignin, and lignosulfonates at a similar rate, producing small-molecular-weight (∼1,000) soluble products which comprised 25 to 35% of the original lignins. At concentrations of 1 g of lignin liter −1 , 90 to 100% of the acid-insoluble Kraft, alkali straw, and dioxane straw lignins were degraded by 1 g of fungal mycelium liter −1 within an active ligninolytic period of 2 to 3 days. Cultures with biomass concentrations as low as 0.16 g liter −1 could also completely degrade 1 g of lignin liter −1 during an active period of 6 to 8 days. The absorbance at 280 nm of 2 g of lignosulfonate liter −1 increased during the first 3 days of incubation and decreased to 35% of the original value during the next 7 days. The capacity of 1 g of cells to degrade alkali-extracted straw lignin under optimized conditions was estimated to be as high as 1.0 g day −1 . This degradation occurred with a simultaneous glucose consumption rate of 1.0 g day −1 . When glucose or cellular energy resources were depleted, lignin degradation ceased. The ability of P. chrysosporium to degrade the various lignins in a similar manner and at very low biomass concentrations indicates that the enzymes responsible for lignin degradation are nonspecific.