Sun Wuyang, Cao Wenrui, Jiang Mingyu, Saren Gaowa, Liu Jiwei, Cao Jiangfei, Ali Imran, Yu Xinke, Peng Changsheng, Naz Iffat
The Key Lab of Marine Environmental Science and Ecology, Ministry of Education, Ocean University of China Qingdao 266100 China
College of Environmental Science and Engineering, Ocean University of China Qingdao 266100 China.
RSC Adv. 2018 Nov 27;8(69):39710-39720. doi: 10.1039/c8ra07721e. eCollection 2018 Nov 23.
In the present research investigation, 13 indigenous bacteria (from CQ1 to CQ13) were isolated from soil collected from Changqing oil field of Xi'an, China. Four promising biosurfactant producers (CQ1, CQ2, CQ4, and CQ13) were selected through primary screening among these 13 strains, including drop collapse and oil-spreading methods. However, only the strain CQ2 showed the best biosurfactant production and was further screened by hemolytic assay, cetyl trimethyl ammonium bromide (CTAB), surface tension and emulsifying activity. The bacterium CQ2 has the ability to produce about 3.015 g L of biosurfactant using glucose as the sole carbon source without any optimization. The produced biosurfactant could greatly reduce surface tension from 72.66 to 24.72 mN m with a critical micelle concentration (CMC) of 30 mg L and emulsify diesel oil up to 60.1%. The cell-free broth was found to be stable in wide temperature (4-100 °C), pH (6-12) and salinity (2-20%) ranges for surface and emulsifying activity. This biosurfactant was preliminarily found to be of a glycolipid nature as evident from thin-layer chromatographic (TLC) and Fourier transform infra-red spectroscopic (FTIR) analyses. Moreover, CQ2 was able to degrade 54.7% of diesel oil, which surprisingly could form a substantial amount of bioflocculants during the degradation process. Furthermore, the 16S rDNA sequence using the Genbank BLAST tool revealed that isolated CQ2 was closely related to species of genus and, thus, was entitled sp. CQ2. The results of residual diesel oil contents measured by GC-MS showed that C7-C28 hydrocarbons could be degraded by sp. CQ2. Thus, these findings revealed that CQ2 could be applied for remediation of diesel oil/petroleum-contaminated waters and soils on a large scale.
在本研究中，从中国西安长庆油田采集的土壤中分离出13株本土细菌（从CQ1到CQ13）。通过包括液滴塌陷和油扩散法在内的初步筛选，从这13株菌株中选出了4株有潜力的生物表面活性剂产生菌（CQ1、CQ2、CQ4和CQ13）。然而，只有菌株CQ2表现出最佳的生物表面活性剂生产能力，并通过溶血试验、十六烷基三甲基溴化铵（CTAB）、表面张力和乳化活性进行了进一步筛选。细菌CQ2在没有任何优化的情况下，以葡萄糖作为唯一碳源能够产生约3.015 g/L的生物表面活性剂。所产生的生物表面活性剂能够将表面张力从72.66 mN/m大幅降低至24.72 mN/m，临界胶束浓度（CMC）为30 mg/L，并能将柴油乳化至60.1%。发现无细胞发酵液在较宽的温度（4 - 100°C）、pH（6 - 12）和盐度（2 - 20%）范围内，其表面和乳化活性保持稳定。从薄层色谱（TLC）和傅里叶变换红外光谱（FTIR）分析可以初步看出，这种生物表面活性剂具有糖脂性质。此外，CQ2能够降解54.7%的柴油，令人惊讶的是，在降解过程中它能够形成大量的生物絮凝剂。此外，使用Genbank BLAST工具进行的16S rDNA序列分析表明，分离出的CQ2与 属的物种密切相关，因此被命名为 sp. CQ2。通过气相色谱 - 质谱联用（GC - MS）测定的残留柴油含量结果表明，C7 - C28烃类能够被 sp. CQ2降解。因此，这些发现表明CQ2可大规模应用于柴油/石油污染水体和土壤的修复。
