Substrate inhibition kinetics of phenol biodegradation

Phenol biodegradation was studied in batch experiments using an acclimated inoculum and initial phenol concentrations ranging from 0.1 to 1.3 g/L. Phe nol depletion and associated microbial growth were monitored over time to p rovide information that was used to estimate the kinetics of phenol biodegr adation. Phenol inhibited biodegradation at high concentrations, and a gene ralized substrate inhibition model based on statistical thermodynamics was used to describe the dynamics of microbial growth in phenol. For experiment al data obtained in this study, the generalized substrate inhibition model reduced to a form that is analogous to the Andrews equation, and the biokin etic parameters mu(max). maximum specific growth; K-s, saturation constant; and K-i, inhibition constant were estimated as 0.251 h(-1), 0.011 g/L, and 0.348 g/L, respectively, using a nonlinear least squares technique. Given the wide variability in substrate inhibition models used to describe phenol biodegradation, an attempt was made to justify selection of a particular m odel based on theoretical considerations. Phenol biodegradation data from n ine previously published studies were used in the generalized substrate inh ibition model to determine the appropriate form of the substrate inhibition model. In all nine cases, the generalized substrate inhibition model reduc ed to a form analogous to the Andrews equation suggesting the suitability o f the Andrews equation to describe phenol biodegradation data.