The biosurfactants have extensive applications in food and petroleum microbiology. The aims of this research were isolation and characterization of thermo-tolerant biosurfactants from highly producing yeast strains. The Bushnell Hass medium was used for screening the biosurfactant-producing yeasts. Biosurfactant presence was evaluated using oil displacement assay and surface tension test. The best biosurfactant-producing strain was named Candida keroseneae GBME-IAUF-2 and its 5.8s-rDNA sequence was deposited in GenBank, NCBI, under the accession number MT012957.1. The thin layer chromatography and Fourier-transform infrared spectroscopy analysis confirmed that the extracted biosurfactant was sophorolipid with a significant surface activity. The purified sophorolipid decreased the surface tension of water from 72 to 29.1 mN/m. Its maximum emulsification index, E_24%, was recorded as 60% and preserved 92.06–97.25% of its original activity at 110–120°C. It also preserved 89.11% and 84.73% of its original activity in pH of 9.3 and 10.5, respectively. It preserved 96.66–100% of its original activity in saline extreme conditions. This is the first report of sophorolipid production by the yeast C. keroseneae. According to the high thermal, pH and saline stability, the sophorolipid produced by C. keroseneae GBME-IAUF-2 could be highly recommended for applications in microbial enhanced oil recovery as well as food industries as an excellent emulsifying agent.

中文翻译：

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新型生产槐糖脂的念珠菌念珠菌GBME-IAUF-2作为微生物提高油采收率（MEOR）的潜在药物。

生物表面活性剂在食品和石油微生物学中具有广泛的应用。这项研究的目的是从高产酵母菌株中分离和鉴定耐热生物表面活性剂。Bushnell Hass培养基用于筛选产生生物表面活性剂的酵母。使用油置换试验和表面张力测试评估生物表面活性剂的存在。产生最佳生物表面活性剂的菌株命名为假丝酵母念珠菌GBME-IAUF-2及其5.8s-rDNA序列存放在NCBI的GenBank中，登录号为MT012957.1。薄层色谱和傅里叶变换红外光谱分析证实，提取的生物表面活性剂是槐糖脂，具有明显的表面活性。纯化的槐糖脂将水的表面张力从72降低到29.1 mN / m。它的最大乳化指数E _24％记录为60％，在110-120°C时保留其原始活性的92.06-97.25％。在pH 9.3和10.5时，它还分别保留了其原始活性的89.11％和84.73％。在极端盐碱条件下，它保留了其原始活性的96.66–100％。这是酵母C. oseoseneae生产槐糖脂的首次报道。。根据高的热，pH和盐水稳定性，所生产的槐糖脂C. keroseneae GBME-IAUF-2可高度推荐用于微生物采油应用以及食品工业中作为优良的乳化剂。