The growth behaviour of using various concentrations of benzoate was investigated. In batch culture, growth was exponential and growth rate (μ) and yields () were high [μ = 0.51 h and = 0.56 mol carbon (mol carbon)] when low concentrations of benzoate (< 5 mM) were used. These kinetic parameters were close to the maxima determined in a benzoate-limited chemostat [μ = 0.55 h and = 0.57 mol carbon (mol carbon)] and the part of the energy for maintenance was limited ( = 4.3 ± 2.2 mmol ATP g h). When higher concentrations of benzoate were used (up to 40 mM), several metabolic limitations appeared. The specific rate of benzoate consumption was not altered, whereas growth was inhibited [i (benzoate) # 27 mM]. Furthermore, high concentrations of catechol together with some 1,2-dihydro-1,2-dihydroxybenzoate (DHB) transiently accumulated in the medium. The accumulation of catechol was attributed to limiting flux through catechol 1,2-dioxygenase estimated to be 5-2 mmol g h, whereas that of DHB was provoked by an imbalance in the NADH/NAD intracellular content. The direct consequence of DHB accumulation was the induction of the pathway for the degradation of catechol, and this pathway contributed up to 20% of the total flux of catechol to the central metabolism. Finally, when very high concentrations of benzoate were used (55 mM), both growth and the specific rate of benzoate degradation were diminished due to a strong decrease in benzoate 1,2-dioxygenase specific activity.


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