Growth inhibition of biomass adapted to the degradation of toluene and xylenes in mixture in a batch reactor with substrates supplied by pulses.

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A biomass adapted to degrade toluene and xylenes in mixture was grown in a batch reactor with substrates supplied by pulses. The inhibition of biomass growth in the course of substrate degradation was investigated. The maximal biomass concentration of 7 g l-1 was obtained using 150 microliters of toluene and 15 microliters of a mixture of xylenes in one litre of liquid medium, and the maximal biomass productivity and yield were 53 mg l-1 h-1 and 0.32 gDW gs-1, respectively. Higher quantities of substrate added by pulses, that is 200 microliters of toluene with 20 microliters of xylenes and 300 microliters of toluene with 30 microliters of xylenes, caused an accumulation of metabolites. These higher quantities of substrates caused inhibition of microbial growth. Among the metabolites produced, 4-methyl catechol was found in large quantities in the culture medium and in the cells.