Jiang Ruizhao, Cai Lu, Wang Miaomiao, Yu Huimin
Department of Chemical Engineering, Tsinghua University, Beijing, 100084, PR China.
Key Laboratory for Industrial Biocatalysis, The Ministry of Education, PR China.
Biotechnol Notes. 2022 Oct 22;3:75-78. doi: 10.1016/j.biotno.2022.10.001. eCollection 2022.
Lipopeptides, novel biosurfactants showing versatile promising applications in enhanced oil recovery, textile industry, agriculture and daily chemical products, etc., are profoundly highlighted recently. Surfactin is one of the most typical representatives of lipopetide family. The critical micelle concentration (CMC) of surfactin is as low as 10-20 mg/L. When its concentration reaches above the CMC, different micelle structure will be formed and the surface-active performances might be changed with varied micelle morphologies. Thus, observation of the changes of surfactin micellar form at different concentrations is of great significance for its new applications. But so far, the micelle structure of surfactin (and also other lipopeptide molecules) is not reported yet, and the method for effectively observing the micelle morphology is limited as well. Here, we developed a method based on transmission electron microscopy combined with negative staining to observe the morphology of surfactin micelles, with which we can clearly observe the changes of micelle morphology of surfactin (or other lipopeptides) at different concentrations. Spherical micelles only form when the concentration of surfactin is low. With the increase in concentration, rod-shaped micelles of surfactin can form. Furthermore, complex rod-shaped-micelle-layer and big ring structure will form when the concentration of surfactin is very high.
脂肽作为一种新型生物表面活性剂，在提高石油采收率、纺织工业、农业和日用化工产品等领域展现出广泛且具有前景的应用，近来受到了广泛关注。表面活性素是脂肽家族最典型的代表之一。表面活性素的临界胶束浓度（CMC）低至10 - 20毫克/升。当其浓度达到CMC以上时，会形成不同的胶束结构，且表面活性性能可能会随胶束形态的变化而改变。因此，观察不同浓度下表面活性素胶束形态的变化对其新应用具有重要意义。但迄今为止，表面活性素（以及其他脂肽分子）的胶束结构尚未见报道，有效观察胶束形态的方法也很有限。在此，我们开发了一种基于透射电子显微镜结合负染色的方法来观察表面活性素胶束的形态，利用该方法我们可以清晰地观察到不同浓度下表面活性素（或其他脂肽）胶束形态的变化。当表面活性素浓度较低时仅形成球形胶束。随着浓度的增加，表面活性素会形成棒状胶束。此外，当表面活性素浓度非常高时，会形成复杂的棒状胶束层和大环结构。
