Influence of phenolic substrates utilised by yeast Trichosporon cutaneum on the degradation kinetics

The degradation kinetics of different phenolic substrates utilised by Trichosporon cutaneum R57 was studied. The following compounds were used as substrates: phenol, resorcinol, hydroquinone, 3-nitrophenol, 2,6-dinitrophenol, 3-chloro phenol and p-cresol. The specific degradation rates (Qs ) were described by a Haldane kinetic model. The unknown model parameters were estimated using the mathematical optimisation procedure for direct search. The results obtained demonstrated that Qs varied greatly in the experiments carried out. The level of biodegradability depended on the different structure and toxicity of compounds used as carbon substrates. The highest Qs values were observed for less toxic hydroxylated phenols (0.77-0.85 h-1), while the most toxic chlorinated phenols were characterised with the lowest Qs values (0.224 h-1). The results obtained with different concentrations of resorcinol (from 0.2 to 0.8 g L-1) and 2,6-dinitrophenol (from 0.2 to 0.7 g L-1) demonstrated a growing inhibitory effect directly correlating with the extended time necessary for complete degradation of both compounds.