Nutritional Regulation of Lignin Degradation by Phanerochaete chrysosporium

Abstract

Previous studies have shown that a lignin-degrading system appears in cultures of the white rot fungus P. chrysosporium in response to nitrogen starvation, apparently as part of secondary metabolism. The influence of limiting carbohydrate, sulfur, or phosphorus and the effect of varying the concentrations of 4 trace metals, Ca2+ and Mg2+ were examined. Limitation of carbohydrate or sulfur but not limitation of phosphorus triggered ligninolytic activity. When only carbohydrate was limiting, supplementary carbohydrate caused a transient repression of activity. In carbohydrate-limited cultures, ligninolytic activity appeared when the supplied carbohydrate was depleted and this activity was associated with a decrease in mycelial dry weight. The amount of lignin degraded depended on the amount of carbohydrate provided, which determined the amount of mycelium produced during primary growth. Carbohydrate-limited cultures synthesized only small amounts of the secondary metabolite veratryl alcohol compared with nitrogen-limited cultures. L-glutamate sharply repressed ligninolytic activity in carbohydrate-starved cultures but NH4+ did not. Ligninolytic activity was also triggered in cultures supplied with 37 .mu.M sulfur as the only limiting nutrient. The balance of trace metals, Mg2+ and Ca2+ was important for lignin degradation.