Kinetic characterization of toluene biodegradation by Rhodococcus erythropolis: Towards a rationale for microflora enhancement in bioreactors devoted to air treatment

• The kinetic characterization of Rhodococcus erythropolis was performed using toluene as a model VOC.
• The Luedeking–Piret correlation described accurately the CO2 production.
• R.erythropolis can be used for boosting bioreactors treating low toluene concentrations.
• Toluene mineralization was mainly related to biomass growth.

The kinetic characterization of microorganisms degrading volatile organic compounds (VOCs) is difficult due to the low substrate concentration prevailing in these processes. In this work, a simple, accurate and easy-to-implement methodology was proposed to perform the kinetic characterization of VOC-degrading microorganisms. The methodology was applied to Rhodococcus erythropolis using toluene as a model VOC. Besides the assessment of traditional kinetic parameters such as the maximum specific growth rate (μmax), substrate half-saturation (KS) and substrate inhibition (KI), the methodology here proposed yielded the α/β kinetic parameter, which indicates the relative relevance of the biomass growth rate and bacterial density on the VOC mineralization performance. R.erythropolis exhibited KS, KI and μmax values of 0.39 g m−3, 54 g m−3 and 0.21 h−1, respectively. The potential of this microorganism (supporting extremely low KS and high KI values) for boosting the performance of bioreactors treating low toluene concentrations was highlighted. Furthermore, α/β ratios of ∼50 to ∼500 were recorded at initial toluene gas concentrations of 1.5–5.2 g m−3, respectively. These α/β ratios indicated that toluene mineralization under the working conditions was mainly related to the biomass growth rather than to the biomass concentration.

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