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

Abstract

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 μl of toluene and 15 μl 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 g_DW g ⁻¹_s , respectively. Higher quantities of substrate added by pulses, that is 200 μl of toluene with 20 μl of xylenes and 300 μl of toluene with 30 μl 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.