Abstract: A bacterial strain，designated as X3，which had the capability to degrade crude oil，was isolated from crude oil-polluted soil in the Dagang oil-field. The ability of strain X3 in the biodegradation of crude oil was studied，and the effects of different crude oil concentrations on the biodegradation of oil and the growth of bacteria were compared . The influence of different pH values and the concentration of NaCl on the biodegradation of crude oil were also investigated. The results showed that strain X3 was resistant to alkali and salt. The concentration of crude oil had a significant influence on the degradation rate of total petroleum hydrocarbons (TPH). When pH was 7 and the concentration of NaCl was 5g/L，X3 degraded approx. 72.6% of crude oil at 30℃ for 7 days. GC analysis showed that carbon number was the greatest factor that influenced the biodegradation. Degradation became more difficult with increasing carbon number of hydrocarbon.

摘要： 从大港油田的石油污染土壤中筛选出一株高效原油降解菌株X3，研究了该菌株对原油的降解能力，比较了不同浓度下的原油对细菌生长和降解率的影响，同时还研究了pH值和盐浓度对该菌株降解原油能力的影响。研究结果表明该菌株具有一定的耐碱性和耐盐性，原油浓度对总石油烃（TPH）的降解速率有很大影响，在30℃、原油初始浓度为1000 mg/L、pH值为7、NaCl浓度为5 g/L的条件下，该菌株对原油的去除效果最佳，可达到72.6%。色谱分析表明碳数是影响石油烃组分降解的最大因素，碳数越大降解越难进行。