鼠李糖脂组分可控生产菌的构建及其鼠李糖脂性能

Construction of mono/di-rhamnolipid ratios-manipulable strains and characterization of their corresponding surfactants' activity

摘要:

鼠李糖脂(rhamnolipids, RLs)被认为是最具有应用潜力的生物表面活性剂之一。由于其单鼠李糖脂与双鼠李糖脂的比例对其性能有着重要的影响，因此构建鼠李糖脂组分可调控的生产菌更有利于其在不同的场景中应用。本研究通过敲除铜绿假单胞菌PAO1中编码鼠李糖基转移酶的基因(rhlC)，获得只产单鼠李糖脂的菌株；然后通过将受阿拉伯糖诱导表达的P_BAD-rhlC基因以整合到染色体上的方式或在质粒上表达的方式进行回补，得到两种类型的回补菌株。结果表明，随着阿拉伯糖诱导浓度的增加，回补菌株合成的鼠李糖脂中单鼠李糖脂所占的比例逐渐降低，表面张力逐渐升高、临界胶束浓度(critical micelle concentration, CMC)值逐渐升高和乳化能力逐渐减弱。未诱导的回补菌株可以产生少量的双鼠李糖脂，合成的鼠李糖脂的表面性能更优，而0.10%阿拉伯糖诱导的鼠李糖脂表现出更好的抑菌效果。

Abstract:

Rhamnolipids (RLs) have emerged as one of the most promising classes of biosurfactants. The ratio of mono-RL to di-RL plays a significant role in determining its performance. Therefore, strains whose production of mono-RL and di-RL are manuplable, have advantage on applications in various scenarios. In this study, we developed a rhlC deletion mutant strain in Pseudomonas aeruginosa PAO1, which produced primarily mono-RL. Subsequently, we generated two complemented strains by integrating the arabinose-induced P_BAD-rhlC gene, either directly into the chromosomes or expressing it on plasmids. Our results indicate that the ratio of mono-RL to di-RL synthesized by the complemented strain gradually decreased as the concentration of arabinose (the inducer) increased. Consequently, there was a decrease in emulsification ability and an increase in surface tension and critical micelle concentration (CMC) of the corresponding rhamnolipids. The complemented strains without inducer can produce a small amount of di-rhamnolipids, which enhanced the surfactant properties. Notably, the rhamnolipids induced by 0.10% arabinose exhibited the most potent antibacterial effect.