KINETICS OF BIODEGRADATION OF GASOLINE AND ITS HYDROCARBON CONSTITUENTS

Aerobic biodegradation of gasoline and its constituents: benzene, tolu ene and ethylbenzene were studied by an enrichment from soil indigenou s microbial population. The enrichment culture completely degraded 16. 1-660 mg/l gasoline in 2.5-16 days respectively, without accumulation of any by-products. The kinetics of gasoline as well as benzene, tolue ne and ethylbenzene biodegradation was investigated with initial gasol ine concentrations of 16.1-62.6 mg/l. The maximum specific rates of bi odegradation of benzene, toluene and ethylbenzene were 0.12, 0.38 and 0.19 mg mg biomass(-1) day(-1) respectively. When benzene and toluene were used as sole substrate? the maximum specific rates of their biode gradation were 62.9 and 16.4 times greater than the corresponding valu es for a mixture (gasoline). The microbial culture was able to mineral ize up to 200 mg/l pure toluene and benzene. Maximum mineralization ef ficiencies of benzene and toluene were 76.7 +/- 5.1% and 76.8 +/- 1.3% respectively. Self-inhibition and competitive inhibition patterns wer e observed during the biodegradation of benzene and toluene alone and in the mixture respectively. The observed kinetics was modeled accordi ng to Andrews' inhibition model.