Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Tianjin Engineering Center of Environmental Diagnosis and Contamination Remediation, College of Environmental Science and Engineering, Nankai University, Tianjin 300071, China.
Sci Total Environ. 2019 Aug 15;678:438-447. doi: 10.1016/j.scitotenv.2019.04.383. Epub 2019 Apr 27.
Anaerobic degradation of petroleum hydrocarbons (PH) is an important process in contaminated environment. The application of rhamnolipids in anaerobic degradation of PH was not extensively studied and inconclusive. This study explored the combined effect of rhamnolipids and electron acceptors on the anaerobic degradation process of total petroleum hydrocarbons (TPH) in sediment from an oil field. The results indicated that rhamnolipids decreased the surface tension of the medium and increased the desorption of TPH from the sediment. After 10-wk culture, the maximum degradation rate of TPH in nitrate and sulfate condition was found to be 32.2% and 24.0%, respectively, with rhamnolipids concentration of 150 mg/L. The addition of 45 and 150 mg/L rhamnolipids increased the degradation rate of TPH but the promotion effect was weakened in the treatment with 450 mg/L rhamnolipids. The copy number of two degradation genes (1-methylalkyl) succinate synthase gene (masD) and 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase gene (bamA) increased with incubation time and showed higher copy numbers in treatments with 45 and 150 mg/L rhamnolipids. In the first week, with the increase of rhamnolipids concentration, the copy number of 16S rDNA increased rapidly and the concentration of electron receptors decreased correspondingly. Moreover, no nitrate was detected in treatments of nitrate with 450 mg/L rhamnolipids after the first week. Microbial community structure analysis result showed that Thiobacillus was the dominant bacteria in all treatments with nitrate as electron acceptor and its proportion gradually decreased with the increase of rhamnolipids concentration. The addition of rhamnolipids changed the subdominant bacteria in the treatments with nitrate as electron acceptor. Methanothrix was the dominant archaea in all treatments with rhamnolipids content of lower than 45 mg/L. When the rhamnolipids concentration increased, the dominant archaea changed to Methanogenium or Methanobacterium. In conclusion, suitable concentrations of rhamnolipids could promote the anaerobic degradation of PH in the sediment.
石油烃 (PH) 的厌氧降解是污染环境中的一个重要过程。鼠李糖脂在 PH 的厌氧降解中的应用尚未得到广泛研究，结论也不一致。本研究探讨了鼠李糖脂和电子受体联合作用对油田沉积物中总石油烃 (TPH) 厌氧降解过程的影响。结果表明，鼠李糖脂降低了介质的表面张力，增加了 TPH 从沉积物中的解吸。在 10 周的培养后，发现硝酸盐和硫酸盐条件下 TPH 的最大降解率分别为 32.2%和 24.0%，鼠李糖脂浓度为 150mg/L。添加 45 和 150mg/L 鼠李糖脂可提高 TPH 的降解率，但在添加 450mg/L 鼠李糖脂的处理中，促进作用减弱。两种降解基因（1-甲基烷基琥珀酸合酶基因 (masD) 和 6-氧环己-1-烯-1-羰基-CoA 水解酶基因 (bamA) 的拷贝数随孵育时间增加而增加，在添加 45 和 150mg/L 鼠李糖脂的处理中具有更高的拷贝数。在第一周，随着鼠李糖脂浓度的增加，16S rDNA 的拷贝数迅速增加，相应地，电子受体的浓度降低。此外，在添加 450mg/L 鼠李糖脂的硝酸盐处理中，第一周后未检测到硝酸盐。微生物群落结构分析结果表明，硝酸盐作为电子受体的所有处理中，硫杆菌是优势细菌，随着鼠李糖脂浓度的增加，其比例逐渐降低。添加鼠李糖脂改变了硝酸盐作为电子受体的处理中的次优势细菌。所有添加鼠李糖脂浓度低于 45mg/L 的处理中，甲烷八叠球菌是优势古菌。当鼠李糖脂浓度增加时，优势古菌变为甲烷生成菌或甲烷杆菌。总之，适当浓度的鼠李糖脂可以促进沉积物中 PH 的厌氧降解。
