Optimization of nutrient component for diesel oil degradation by Acinetobacter beijerinckii ZRS.

A new bacterial strain that is capable of using diesel as the sole carbon source was isolated from the petroleum-contaminated soil of Xinjiang oil field, Northwest China. This bacterium was identified on the basis of its morphological and physiological characteristics and 16S rRNA gene sequence analysis, and it showed the greatest similarity with Acinetobacter beijerinckii 302-PWB-OH1 (99.86%). In order to enhance degradation efficiency, single-factor experiments and response surface methodology (RSM) were employed to optimize the nutrients used in artificial seawater. The results of this study revealed that 2.05 g L(-1) (NH4)2SO4, 1.46 g L(-1) Na2HPO4, and 14 mg L(-1) yeast extract in artificial seawater resulted in increasing the diesel degradation rate of the bacterial strain from 20.87% to 80.40% within 7 days. The actual experimental results were in agreement with the prediction.

[Biological toxicity effect of petroleum contaminated soil before and after physicochemical remediation].

Toxicity analysis was studied from using seed germination as an ecological indicator, and the earthworm was considered as a suitable biomonitor animal to determine the ecological hazard of polluted soil. The main results are as follows: These crop seeds have significantly different responses to petroleum pollution. Compared with those plants in clean soil, the germination of most crop seeds planted in contaminated soils is obviously inhabited. Soybean, horse bean and maize are the crop affected most adversely. Fortunately, strong endurance is observed for green soybean under 4 different levels of petroleum pollution, and the seed germination rate are all above 90%. When exposed to pollutants, earthworms could be changed obviously on the level of physiology. That might affect the survival and growth capacity of earthworms, and changed population finally. In high petroleum contaminated soil (concentration of petroleum > 30 000 mg/kg) earthworms can only survive about 5 days. The results suggest that petroleum pollution has great poison to earthworms and can kill earthworms finally. Because pollutants make them dehydrate. Even on the low pollution level, the survival time of earthworm is still very short (3 d or so) in the treated petroleum-contaminated soil. Because after a petroleum ether-treated, the nutrients of soil are disposed with the oil, and the organic matter and other nutrients of the soil have a great impact on the survival of earthworms.

Degradation of MTBE and TBA by a new isolate from MTBE-contaminated soil.

Methyl tert-butyl ether (MTBE), a gasoline additive, possesses serious problems to the environmental health. In the present study, a bacterial culture named A-3 which could effectively degrade MTBE was isolated from the MTBE contaminated soil. The isolate was identified as Chryseobacterium sp., a new species capable of degrading MTBE. In order to enhance its degradation ability, selected environment factors were investigated. The results showed that the optimal temperature was in the range of 25-30 degrees C, the pH was 7.0, the inoculum size was 2 x 10(8) CFU/ml and the optimal concentration of MTBE was from 50 to 100 mg/L. The maximum MTBE utilization rate (upsilon(max)) was 102 nmol MTBE/(mg cell protein x h). Furthermore, it was found that the isolate could also degrade tert-butyl alcohol (TBA). The degradation rates of TBA were much faster than those of MTBE. The additional TBA would lead to the decrease of the initial MTBE degradation rate and the inhibitory effect of TBA increased with the increase of TBA concentration. Similar protein profiles at least seven peptides were demonstrated after SDS-PAGE analysis of crude extracts obtained from the cells growing in MTBE and TBA culture.