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To determine the liquid culture conditions under which the wood-degrading system of the brown-rot fungus Gloeophyllum trabeum is expressed, enzymes and metabolites from liquid and solid substrate cultures were characterized. Enzymes were analyzed by 2-D gel electrophoresis and also assayed. Growth conditions were varied by using liquid media containing: (1) low carbon, low nitrogen, (2) low carbon, high nitrogen, (3) high carbon, low nitrogen, or (4) high carbon, high nitrogen. The protein arrays expressed under the four conditions were very similar, and endo-1,4-β-glucanase (detected by 2-D gels) activity along with β-glucosidase, xylanase, and NADH/quinone oxidoreductase activities were detected. Maximal expression of the hydrolytic enzymes was observed in high carbon/high nitrogen medium, whereas the highest oxidoreductase activity was in the high carbon low nitrogen medium. Oxalate and 2,5-dimethoxybenzoquinone were detected under all culture conditions, with higher production in high carbon/low nitrogen medium. Cultures grown in this medium also yielded the highest rate of hydroxylation of p-hydroxybenzoic acid, yielding protocatechuic acid, a product of hydroxyl radical attack.