Modeling of growth kinetics for Pseudomonas putida during toluene degradation

Abstract

Glucose has been often used as a secondary substrate to enhance the degradation of primary substrate as well as the increase of biomass, especially for the inhibitory range of substrate concentration. In this study, we investigated the effect of glucose concentration on growth kinetics of Pseudomonas putida during toluene degradation for a wide concentration range (60-250 mg/l). Batch microcosm studies were conducted in order to monitor bacterial growth for three different initial concentrations (2, 5, 10 mg/ml) of glucose for a given toluene concentration. Modeling of growth kinetics was also performed for each growth curve of glucose dose using both Monod and Haldane kinetics. Batch studies revealed that bacterial growth showed a distinct inhibitory phase above some limit (similar to 170 mg/l) for the lowest (2 mg/ml) glucose dose, but the degree of inhibition decreased as the glucose dose increased, leading to three different growth patterns. The bacterial growth followed each of the modified Wayman and Tseng, Wayman and Tseng, and Luong model as the glucose dose increased from 2 to 10 mg/ml. This indicates that glucose has a prominent influence on bacterial growth during toluene degradation and that different kinetics should be adopted for each broth condition.