Study On The Improvement Of Thermostable Petroleum Degradation Strains And The Promotion Factors Of Degradation

To modify the bioremediation of the petroleum contaminated soil in high temperature and arid area, UV-microwave mutagenesis technology was used to improve the existing petroleum degradation strains. The three factors of environment, nutrient balance and biology were studied on their promotion on the efficient and thermostable petroleum degradation strains UM1. Then UM1was used in bioremediation of the petroleum contaminated gray-brown desert soil in high temperature and arid area.After4times of UV mutagenesis (100s for each) and twice microwave mutagenesis (45s for each) on KO5-2-11, the efficient and thermostable petroleum degradation strain UM2-6was obtained. Refering to this method,KL9-1-2and KL8-2-5were improved to UM4-land UM3-4, respectively. The mixed strain UM1was the mixture of the above three petroleum degradation strains in equal ratio. After being cultured for7days at50℃and160rpm, its petroleum degradation rate was50.68%with very good genetic stability. Even at the high temperature of60℃, UM1still had a petroleum degradation rate of25.45%, showing good thermostable performance. The petroleum degradation rate of UM1reached the highest value of56.14%at45℃, showing obvious improvement. Meanwhile, UM1grew rapidly and the petroleum degradation rate could reached the highest value after6days of culture.The various following factors could promote the petroleum degradation effects of UM1: the temperature of environment, initial pH, rotation speed, concentration of NaCl and initial concentration of petroleum, the kinds of nitrogen and phosphorus sources of nutrition balance factors, nitrogen-phosphorus ratio, content of calcium and magnesium ions, biological factor of inoculation amount and the additiveamount of yeast extract. Based on the analysis of orthogonal experiment, rotation speed and inoculation were the main factors affecting the petroleum degradation and pH was the least factor. The optimal promotion factors for UM1wereinitial pH7, inoculation amount4mL, nitrogen-phosphorus ratio5:1, rotation speed140rpm, culture time6d. Under these conditions, the petroleum degradation rate reached65.04%. The simulation experiment of single factor soil remediation showed that with25mL of the UM1strain suspension, nitrogen-phosphorus ratio of5:1,0.75%of the SDBS,8%of sawdust and the petroleum content of3%, the remediation performed well. Response surface optimization of the four factors of inoculation amount, nitrogen-phosphorus ratio, SDBS dosage and the sawdust addition showed that and the optimal remediation conditions were inoculation amount27.9mL, nitrogen-phosphorus ratio5.3:1, SDBS dosage0.9%and the sawdust additiveamount9.1%. In addition, the petroleum degradation prediction model fitting was also achieved. During the remediation, the urease activity rose rapidly at the beginning, then decreased slightly. However, dehydrogenase and polyphenol oxidase activity continued to increase, showing positive correlation with petroleum degradation rate. The number of bacteria and actinomycetes in the repairing process increased constantly. After entering the logarithmic growth phase, the number of fungi began to decline and the number of microorganism and petroleum degradation rate was positively correlated. In the process of remediation, the biodegradability on the four components in petroleum hydrocarbons deceased in the order of saturated hydrocarbon, aromatics, colloid and asphaltene.