A metabolic role of the glyoxylate and tricarboxylic acid cycles for development of the copper-tolerant brown-rot fungus Fomitopsis palustris.

Fruit bodies of the copper-tolerant brown-rot fungus Fomitopsis palustris were produced in liquid medium for the first time. To induce fruit body formation of this fungus, it was important to inoculate the liquid medium with mycelia grown on potato dextrose agar plates and also to adjust the initial pH of the medium to 5.0. The metabolic role of the glyoxylate and tricarboxylic acid cycles during fungal development in the liquid culture was investigated in relation to oxalate biosynthesis. The enzymes for the glyoxylate cycle and oxalate biosynthesis in mycelium showed greater activities at the vegetative growth stage than at the fruiting stage. The ratios of isocitrate dehydrogenase activity to isocitrate lyase activity in mycelium were 0.3 and 4.0 at the vegetative and fruiting stage, respectively. Thus, isocitrate lyase of the glyoxylate cycle played a more important role in oxalate synthesis at the earlier stage of the cultivation, whereas isocitrate dehydrogenase played a major role in glutamate synthesis during fruit body formation.