Biodegradation of 2-chlorobenzoic acid by klebsiella oxytoca: Mathematical modeling and effect of some growth conditions

Klebsiella oxytoca was grown in batch cultures using a 2-chlorobenzoic acid (2-CBA) containing minimal salt medium. 2-CBA was the sole source for carbon and energy.¹H NMR and electron-impact mass spectra results suggested an ortho-cleavage pathway of the 2-CBA degradation. An unstructured model with substrate inhibition was successfully applied to the 2-CBA experimental data at different concentrations. The maximum specific growth rate, saturation constant, and substrate inhibition constant were found to be 0.8573 h^-1, 10.441 mM, and 50.95 mM, respectively. All carbon sources exhibited different growth kinetics and caused an increase in bacterial growth several times (2-4 fold). Glucose, sorbitol, and fructose at 0.2% concentration, as additional carbon sources, decreased the initial degradation rates of 2-CBA at ranges of 20-70% lower than that of the control. At the same time, lactose, maltose, and sucrose led to the increase in the 2-CBA biodegradation. Nitrogen sources (except l-prolin) caused an inhibition in 2-CBA degradation by 55, 60, and 33% for yeast extract, casein, and trypton, respectively. The data showed that different initial (inocula) densities affected the induction time for 2-CBA degradation and resulted in the different degradation rates by concentration-dependent manner. 2-CBA degradation was optimally achieved at a 37 °C incubation temperature and a pH of 7.0.