Screening Of N-alkanes-degrating Strains And The Variation Characteristics In The Process Of Degradation

This study illustrated the n-hexadecane degrading-bacteria isolated from petroleum-contaminated soil sampled from Liaohe Oilfield. The identification of physical and chemical properties and the classification of the strains were carried out and also, of which function to metabolize n-hexadecane was determined. The adaptability of bacteria to soil environment was confirmed through the n-hexadecane degradation experiment in a slurry system mixed with the artificial contaminated soil and water. The experiments of the bioremediation and electrokinetic remediation of petroleum-contaminated soil in Liaohe Oilfield tested the variation characteristic of the bacteria community, especially for the target degrading-bacteria in soil environment. The conclusions of the study were as follows:(1) Three strains with great n-hexadecane degradation ability were obtained from the petroleum-contaminated soil in Liaohe Oilfield, named as T1, T2 and T5 respectively. Through the analysis of the growth morphology and the 16 s rDNA sequence, T1 and T5 were identified as Pseudomonas aeruginosa(KR054697), and T2 was identified as Spingopyxis terrae(KR054698). The optimal experimental conditions for the n-hexadecane degradation were temperature 30 °C, pH of 7, C: N: P of 100: 10: 2 and the salinity of 1.5% confirmed by the shaking flasks experiments for the mixed strains.(2) The results of the slurry experiment indicated the great degradation ability of the degrading-bacteria, with 29.3% degradation ratio of n-hexadecane after 30 days of testing. There was high abundance for T2 strain(Spingopyxis terrae) at the primary stage of experiment, and then replaced by T1 and T5 strains(Pseudomonas aeruginosa) showing the advantage of the multiple strains combination applied in bioremediation process. Furthermore, under the weak electric condition(1.2 V·cm-1), the metabolic activity of degrading bacteria was enhanced, with the degradation ratio of n-hexadecane improved by 35.80 % compared to bioremediation after 30 days of treatment. It reflected the synergistic action between electrokinetics and bioremediation and confirmed the feasibility of the application of degrading-bacteria in electric field.(3) In the remediation test of the petroleum-contaminated soil sampled in Liaohe Oilfield, the degradation ratio of alkane reached 37.58 % after 48 days of treatment. The degradation extent of alkane was also improved by 24.39 % under electrokinetics and bioremediation combination. The activity of soil dehydrogenase(DHA) showed the higher value in BIO and EK-BIO treatments than that in EK treatment and a positive correlation exists between the degradation rate of n-hexadecane and DHA activity both in BIO and EK-BIO treatments. The enhanced degradation function originated from the electrical stimulation was illustrated by the higher DHA activity of soil samples in EK-BIO treatment than that in BIO treatment. Others, the soil microbial community diversity was intensified under electrokinetics treatment for the optimized adaptability of the bacteria to the soil environment.This research indicated that the degrading-bacteria screened from the petroleum contaminated soil is not only applicable to bioremediation in soil, but also can be combined with the electrokinetics remediation for organics removal. The experiment conducted in this study provided the theoretical basis for the regulation of the bioremediation and the establishment of the combined remediation technology for the petroleum contaminated soil remediation.