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

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 maxima l biomass concentration of 7 g l(-1) was obtained using 150 mu l of toluene and 15 mu l 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(D )W g s(-1), respectively. Higher quantities of substrate added by pulses, t hat is 200 mu l of toluene with 20 mu l of xylenes and 300 mu l of toluene with 30 mu l of xylenes, caused an accumulation of metabolites. These highe r quantities of substrates caused inhibition of microbial growth. Among the metabolites produced, 4-methyl catechol was found in large quantities in t he culture medium and in the cells.