Enzyme patterns during substrate shifts between phenol, acetate and glucose in continuous culture of Trichosporon cutaneum

Abstract

The soil yeast Trichosporon cutaneum was grown in continuous culture on phenol, acetate or glucose as sole carbon source. The activities of enzymes participating in the tricarboxylic acid cycle, glyoxylate cycle, 3-oxoadipate pathway, pentose phosphate pathway and glycolysis were determined in situ during shifts of carbon sources. Cells grown on phenol or glucose contained basal activity of the glyoxylate-cycle-specific isocitrate lyase. The derepression of the glyoxylate cycle enzymes was partly hindered in the presence of phenol but not in the presence of low levels of glucose. Phenol and glucose caused repression of isocitrate lyase. In the presence of either phenol or glucose, acetate accumulation in the medium increased. However, part of the supplied acetate was utilized simultaneously with phenol or glucose, the utilization rate of either carbon source being reduced in the presence of the other carbon source. Acetate caused repression but not inactivation of the phenol-degrading enzymes, phenol hydroxylase and catechol 1,2-dioxygenase. The simultaneous utilization of phenol and other carbon sources in continuous culture as well as the observed repression-derepression patterns of the involved enzymes reveal T. cutaneum to be an organism of interest for possible use in decontamination processes.