Substrate inhibition kinetics of phenol degradation by binary mixed culture of <i>Pseudomonas aeruginosa</i> and <i>Pseudomonas fluorescence</i> from steady state and wash- out data

Abstract

Steady states of a continuous culture with an inhibitory substrate were used to estimate kinetic parameters under substrate limitation (chemo stat operation). Mixed cultures of an indigenous Pseudomonas fluorescence and Pseudomonas aeruginosa were grown in continuous culture on phenol as the sole source of carbon and energy at dilution rates of 0.01 – 0.20 h-1. Using different dilution rates several steady states were investigated and the specific phenol consumption rates were calculated. In addition, phenol degradation was investigated by increasing the dilution rate above the critical dilution rate (washout cultivation). The results showed that the phenol degradation by mixed culture of P. fluorescence and P. aeruginosa can be described by simple substrate inhibition kinetics under substrate limitation but cannot be described by simple substrate inhibition kinetics under washout
cultivation. The phenol consumption rate (degradation rate) increased with increase in dilution rate. Fitting of the steady state data from continuous cultivation to six inhibition models resulted in the best
fit for Haldane, Yano and Koga, Aiba et al. and Teissier models, respectively. The rsmax value of 0.322 mg/mg/h obtained from these model equations was comparable to the experimentally calculated rsmax value of 0.342 mg/mg/h obtained under washout cultivation.