Comparison of growth kinetics and phenol metabolizing enzymes of Trichosporon cutaneum R57 and mutants with modified degradation abilities

The model kinetic coefficients of the growth and phenol degradation processes of Trichosporon cutaneum R57 strain and the investigated mutants in culture media containing phenol as a sole carbon and energy source are reported. Successfully simulated phenol degradation profiles in all studied strains were obtained by Haldane-type kinetics. The data presented in the paper showed no direct correlation between efficiency of phenol degradation by the strains studied and biomass productivity. The observed significant increase of inhibitory coefficients in both 2R (K-i = 0.46 g l(-1)) and 4R (K-i = 0.44 a l(-1)) mutants corresponded with their improved capacity to degrade phenol and increased phenol hydroxylase activity. The intracellular specific activities of phenol hydroxylase (EC 1.14.13.7) and catechol 1,2-dioxygenase (EC 1.13.11.1) in T cutaneum R57 strain and its mutants are measured. The comparison of data for phenol hydroxylase and catechol 1,2-dioxygenase activities in cell-free extracts obtained by ultra sonication and in permeabilized cells showed that the method of cell permeabilization was more favorable for enzyme analyses. The obtained specific activity of phenol hydroxylase in T cutaneum R57 was 0.8 U mg(-1) protein while those in 2R and 4R mutant strains were 1.47 U mg(-1) protein and 1.28 U mg(-1) protein, respectively. The value of catechol 1,2-dioxygenase activity showed quite less variability and was kept about 0.2 U mg(-1) protein in all investigated strains. The results received in these experiments demonstrated that the increased rate of the initial phenol degradation reaction enhanced phenol utilization by cells and vice versa. (C) 2003 Elsevier Inc. All rights reserved.