College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing, 211816, PR China.
Oil Production Research Institute, Shengli Oil Field Ltd. Co. Sinopec, Dongying, 257000, PR China.
Colloids Surf B Biointerfaces. 2021 Apr;200:111602. doi: 10.1016/j.colsurfb.2021.111602. Epub 2021 Feb 3.
Due to its special structure, the cyclic lipopeptide surfactin showed remarkable responsiveness to stimuli such as pH, temperature and metal ions. However, few studies investigated the effect of fermented by-products on the conformational change and interfacial assembly of surfactin. Here, the effect of acetoin, a primary metabolite of Bacillus subtilis, on the conformational change and interfacial assembly of surfactin was studied in detail. Surface tension measurements showed that the critical micelle concentration (CMC) of surfactin increased from 1.14 × 10 to 4.32 × 10 M in the presence of acetoin. Moreover, acetoin has increased the interfacial tension of surfactin aqueous solution-crude oil from 1.08 mN/m to 3.01 mN/m. Circular dichroism (CD) spectra and dynamic light-scattering (DLS) further demonstrated that acetoin had induced the conformational transition of surfactin from β-sheet to β-turn structure, and caused surfactin forming some larger micelle aggregations. Afterwards, it was further found that acetoin decreased the oil sand cleaning efficiency of surfactin from 59.7% to 6.6%, and deteriorated the O/W emulsion stability and altered the silicate wettability toward less water wet state. Based on the experimental results, a possible mechanism of the interaction between surfactin and acetoin was proposed.
由于其特殊的结构，环状脂肽表面活性剂对 pH 值、温度和金属离子等刺激表现出显著的响应性。然而，很少有研究探讨发酵副产物对表面活性剂构象变化和界面组装的影响。在这里，详细研究了丁二酸芽孢杆菌的一种主要代谢产物乙酰**，对表面活性剂构象变化和界面组装的影响。表面张力测量表明，在乙酰存在下，表面活性剂的临界胶束浓度（CMC）从 1.14×10 增加到 4.32×10 M。此外，乙酰增加了表面活性剂水溶液-原油的界面张力从 1.08 mN/m 增加到 3.01 mN/m。圆二色性（CD）光谱和动态光散射（DLS）进一步表明，乙酰诱导了表面活性剂从β-折叠结构到β-转角结构的构象转变，并导致表面活性剂形成一些较大的胶束聚集物。之后，进一步发现乙酰降低了表面活性剂对油砂的清洁效率从 59.7%到 6.6%，并恶化了 O/W 乳液稳定性，改变了硅酸盐的润湿性，使其向更疏水的状态转变。基于实验结果，提出了表面活性剂与乙酰**相互作用的可能机制。
